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Throughout the 20th century, several styles of avant-garde art helped shape modern art. While many of these genres-including subconscious-based surrealism and energetic abstract expressionism -predominantly favored paintings, the Bauhaus movement encompassed a wide array of mediums, materials, and disciplines.

Ranging from paintings and graphics to architecture and interiors, Bauhaus art dominated many outlets of experimental European art throughout the 1920s and 1930s. Though it is most closely associated with Germany, it attracted and inspired artists of all backgrounds. Today, its influence can be found in art and design all over the world, whether within the walls of a museum or on a suburban street.

What is Bauhaus?

Bauhaus-literally translated to "construction house"-originated as a German school of the arts in the early 20th century. Founded by Walter Gropius, the school eventually morphed into its own modern art movement characterized by its unique approach to architecture and design. Today, Bauhaus is renowned for both its unique aesthetic that inventively combines the fine arts with arts and crafts as well as its enduring influence on modern and contemporary art.

History

In 1919, German architect Walter Gropius established Staatliches Bauhaus, a school dedicated to uniting all branches of the arts under one roof. The school acted as a hub for Europe's most experimental creatives, with well-known artists like Josef Albers, Wassily Kandinsky, and Paul Klee offering their expertise as instructors.

Bauhaus as an educational institution existed in three cities -Weimar (1919 to 1925), Dessau (1925 to 1932), and Berlin (1932 to 1933).

Weimar, aka State Bauhaus in Weimar, was where Gropius laid the groundwork for Bauhaus to come; it's where he established ideals that would be considered visionary for the time. Art, according to his manifesto and the program, should serve a social role and there should no longer be a division of craft-based disciplines.

At Weimar, the "stage workshop" was an important part of the education. It was directed by Lothar Schreyer from 1921 to 1923 and then by Oskar Schlemmer from 1923 to 1925. It brought together visual and performing arts and stressed an interdisciplinary approach.

Dessau was considered the hotspot in the heyday of Bauhaus. It arose after the politically motivated close of Weimar. During this time, it set forth on the path of designing new industrial products for mass consumption. (Most of the products and designs that are well known today came from Dessau.) It was also here that the famous Bauhaus Building was planned and built by Gropius. This iteration of Bauhaus was dissolved on September 30, 1932.

Berlin was the last phase of Bauhaus. Due to mounting pressures from the Nazis and cutbacks in funding, there was limited work done during this time. The move to Berlin happened after the closure of Dessau, and Bauhaus masters and students reconvened in October 1932 out of an abandoned telephone factory. By April 11, 1933, however, the premises were searched and closed by the police and SA.

The teaching staff dissolved the Bauhaus in July 1933. But even after facing permanent closure, the influence and aesthetic of the school persisted, culminating in the Bauhaus movement.

Style of Bauhaus

The style of Bauhaus is commonly characterized as a combination of the Arts and Crafts movement with modernism, as evident in its emphasis on function and, according to the Tate, its "aim to bring art back into contact with everyday life." Thus, typical Bauhaus designs-whether evident in painting, architecture, or interior design-feature little ornamentation and a focus on balanced forms and abstract shapes.

Bauhaus Art

In art, this emphasis on function is apparent in the balanced compositions of abstract paintings by Bauhaus artists like Wassily Kandinsky and . Undoubtedly inspired by architecture, the paintings typically pair flat planes with overlapping shapes to suggest dimensionality.

In addition to paintings, artists often produced abstract sculptures, avant-garde , and modernist posters featuring bold typography and blocks of color.

Bauhaus Architecture

Similar to Bauhaus art, architecture in this style is characterized by harmoniously balanced geometric shapes and an emphasis on function.

Featuring open plans and lots of glass, it is inspired by the simple yet polished look of the American Arts and Crafts movement-a genre popularized by master architect and Prairie School pioneer Frank Lloyd Wright.

Furthermore, this modern architecture movement heavily inspired the look of mid-century modern homes, which borrow the clean lines and functional design of Bauhaus buildings.

Bauhaus Interior Design

Bauhaus interiors are renowned for their simplicity and openness. The iconic furniture that did adorn these spaces was always highly intentional. Chairs, for instance, were reimagined by Marcel Breuer, who was the head of the cabinet-making workshop at the Bauhaus in Dessau. He wanted to create minimalistic and mass-producible pieces that were made mostly of metal. This resulted in the foldable, lightweight Wassily Chair -named after the painter Wassily Kandinsky.

Although subtle, textiles also played a role in Bauhaus interior design. In fact, students studied color theory as well as weaving in the textile workshop. Their pieces, as well as the occasional wall painting, provided some levity to the otherwise industrial rooms.

Legacy

Today, Bauhaus is often credited as the catalyst for modern architecture and furniture and as an important influence on mid-20th century painting and sculpture. Some buildings-including Bauhaus Dessau, a UNESCO World Heritage Site-have been turned into tourist destinations and house museums, while many major modern art museums incorporate the works of art into their permanent displays and popular exhibitions.

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Bauhaus: How the Avant-Garde Movement Transformed Modern Art

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Throughout the 20th century, several styles of avant-garde art helped shape modern art. While many of these genres-including subconscious-based surrealism and energetic abstract expressionism -predominantly favored paintings, the Bauhaus movement encompassed a wide array of mediums, materials, and disciplines.

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The ( Staatliches Bauhaus ( German: [ˈʃtaːtlɪçəs ˈbaʊˌhaʊs] Bauhaus ( listen )), commonly known as the German for 'building house'), was a German art school operational from 1919 to 1933 that combined crafts and the fine arts.[1] The school became famous for its approach to design, which attempted to unify individual artistic vision with the principles of mass production and emphasis on function.[1]

The Bauhaus was founded by architect Walter Gropius in Weimar. It was grounded in the idea of creating a Gesamtkunstwerk ("comprehensive artwork") in which all the arts would eventually be brought together. The Bauhaus style later became one of the most influential currents in modern design, modernist architecture, and architectural education. The Bauhaus movement had a profound influence upon subsequent developments in art, architecture, graphic design, interior design, industrial design, and typography. Staff at the Bauhaus included prominent artists such as Paul Klee, Wassily Kandinsky, and László Moholy-Nagy at various points.

The school existed in three German cities- Weimar, from 1919 to 1925; Dessau, from 1925 to 1932; and Berlin, from 1932 to 1933-under three different architect-directors: Walter Gropius from 1919 to 1928; Hannes Meyer from 1928 to 1930; and Ludwig Mies van der Rohe from 1930 until 1933, when the school was closed by its own leadership under pressure from the Nazi regime, having been painted as a centre of communist intellectualism. Internationally, former key figures of Bauhaus were successful in the United States and became known as the avant-garde for the International Style.

The changes of venue and leadership resulted in a constant shifting of focus, technique, instructors, and politics. For example, the pottery shop was discontinued when the school moved from Weimar to Dessau, even though it had been an important revenue source; when Mies van der Rohe took over the school in 1930, he transformed it into a private school and would not allow any supporters of Hannes Meyer to attend it.

The Bauhaus style tends to feature simple geometric shapes like rectangles and spheres, without elaborate decorations. Buildings, furniture, and fonts often feature rounded corners and sometimes rounded walls. Other buildings are characterized by rectangular features, for example protruding balconies with flat, chunky railings facing the street, and long banks of windows. Furniture often uses chrome metal pipes that curve at corners.

After Germany's defeat in World War I and the establishment of the Weimar Republic, a renewed liberal spirit allowed an upsurge of radical experimentation in all the arts, which had been suppressed by the old regime. Many Germans of left-wing views were influenced by the cultural experimentation that followed the Russian Revolution, such as constructivism. Such influences can be overstated: Gropius did not share these radical views, and said that Bauhaus was entirely apolitical. Just as important was the influence of the 19th-century English designer William Morris (1834-1896), who had argued that art should meet the needs of society and that there should be no distinction between form and function. Thus, the Bauhaus style, also known as the International Style, was marked by the absence of ornamentation and by harmony between the function of an object or a building and its design.

However, the most important influence on Bauhaus was modernism, a cultural movement whose origins lay as early as the 1880s, and which had already made its presence felt in Germany before the World War, despite the prevailing conservatism. The design innovations commonly associated with Gropius and the Bauhaus-the radically simplified forms, the rationality and functionality, and the idea that mass production was reconcilable with the individual artistic spirit-were already partly developed in Germany before the Bauhaus was founded. The German national designers' organization Deutscher Werkbund was formed in 1907 by Hermann Muthesius to harness the new potentials of mass production, with a mind towards preserving Germany's economic competitiveness with England. In its first seven years, the Werkbund came to be regarded as the authoritative body on questions of design in Germany, and was copied in other countries. Many fundamental questions of craftsmanship versus mass production, the relationship of usefulness and beauty, the practical purpose of formal beauty in a commonplace object, and whether or not a single proper form could exist, were argued out among its 1,870 members (by 1914).

German architectural modernism was known as Neues Bauen. Beginning in June 1907, Peter Behrens' pioneering industrial design work for the German electrical company AEG successfully integrated art and mass production on a large scale. He designed consumer products, standardized parts, created clean-lined designs for the company's graphics, developed a consistent corporate identity, built the modernist landmark AEG Turbine Factory, and made full use of newly developed materials such as poured concrete and exposed steel. Behrens was a founding member of the Werkbund, and both Walter Gropius and Adolf Meyer worked for him in this period.

The Bauhaus was founded at a time when the German zeitgeist had turned from emotional Expressionism to the matter-of-fact New Objectivity. An entire group of working architects, including Erich Mendelsohn, Bruno Taut and Hans Poelzig, turned away from fanciful experimentation and towards rational, functional, sometimes standardized building. Beyond the Bauhaus, many other significant German-speaking architects in the 1920s responded to the same aesthetic issues and material possibilities as the school. They also responded to the promise of a "minimal dwelling" written into the new Weimar Constitution. Ernst May, Bruno Taut and Martin Wagner, among others, built large housing blocks in Frankfurt and Berlin. The acceptance of modernist design into everyday life was the subject of publicity campaigns, well-attended public exhibitions like the Weissenhof Estate, films, and sometimes fierce public debate.

The Vkhutemas, the Russian state art and technical school founded in 1920 in Moscow, has been compared to Bauhaus. Founded a year after the Bauhaus school, Vkhutemas has close parallels to the German Bauhaus in its intent, organization and scope. The two schools were the first to train artist-designers in a modern manner. Both schools were state-sponsored initiatives to merge traditional craft with modern technology, with a basic course in aesthetic principles, courses in color theory, industrial design, and architecture. Vkhutemas was a larger school than the Bauhaus, but it was less publicised outside the Soviet Union and consequently, is less familiar in the West.

With the internationalism of modern architecture and design, there were many exchanges between the Vkhutemas and the Bauhaus. The second Bauhaus director Hannes Meyer attempted to organise an exchange between the two schools, while Hinnerk Scheper of the Bauhaus collaborated with various Vkhutein members on the use of colour in architecture. In addition, El Lissitzky's book Russia: an Architecture for World Revolution published in German in 1930 featured several illustrations of Vkhutemas/Vkhutein projects there.

The school was founded by Walter Gropius in Weimar on 1 April 1919, as a merger of the Grand-Ducal Saxon Academy of Fine Art and the Grand Ducal Saxon School of Arts and Crafts for a newly affiliated architecture department. Its roots lay in the arts and crafts school founded by the Grand Duke of Saxe-Weimar-Eisenach in 1906, and directed by Belgian Art Nouveau architect Henry van de Velde. When van de Velde was forced to resign in 1915 because he was Belgian, he suggested Gropius, Hermann Obrist, and August Endell as possible successors. In 1919, after delays caused by World War I and a lengthy debate over who should head the institution and the socio-economic meanings of a reconciliation of the fine arts and the applied arts (an issue which remained a defining one throughout the school's existence), Gropius was made the director of a new institution integrating the two called the Bauhaus. In the pamphlet for an April 1919 exhibition entitled Exhibition of Unknown Architects, Gropius, still very much under the influence of William Morris and the British Arts and Crafts Movement, proclaimed his goal as being "to create a new guild of craftsmen, without the class distinctions which raise an arrogant barrier between craftsman and artist." Gropius's neologism Bauhaus references both building and the Bauhütte, a premodern guild of stonemasons. The early intention was for the Bauhaus to be a combined architecture school, crafts school, and academy of the arts. Swiss painter Johannes Itten, German-American painter Lyonel Feininger, and German sculptor Gerhard Marcks, along with Gropius, comprised the faculty of the Bauhaus in 1919. By the following year their ranks had grown to include German painter, sculptor, and designer Oskar Schlemmer who headed the theatre workshop, and Swiss painter Paul Klee, joined in 1922 by Russian painter Wassily Kandinsky. A tumultuous year at the Bauhaus, 1922 also saw the move of Dutch painter Theo van Doesburg to Weimar to promote ("The Style"), and a visit to the Bauhaus by Russian Constructivist artist and architect El Lissitzky.

From 1919 to 1922 the school was shaped by the pedagogical and aesthetic ideas of Johannes Itten, who taught the Vorkurs or "preliminary course" that was the introduction to the ideas of the Bauhaus. Itten was heavily influenced in his teaching by the ideas of Franz Cižek and Friedrich Wilhelm August Fröbel. He was also influenced in respect to aesthetics by the work of the Der Blaue Reiter group in Munich, as well as the work of Austrian Expressionist Oskar Kokoschka. The influence of German Expressionism favoured by Itten was analogous in some ways to the fine arts side of the ongoing debate. This influence culminated with the addition of Der Blaue Reiter founding member Wassily Kandinsky to the faculty and ended when Itten resigned in late 1923. Itten was replaced by the Hungarian designer László Moholy-Nagy, who rewrote the Vorkurs with a leaning towards the New Objectivity favoured by Gropius, which was analogous in some ways to the applied arts side of the debate. Although this shift was an important one, it did not represent a radical break from the past so much as a small step in a broader, more gradual socio-economic movement that had been going on at least since 1907, when van de Velde had argued for a craft basis for design while Hermann Muthesius had begun implementing industrial prototypes.

Gropius was not necessarily against Expressionism, and in fact, himself in the same 1919 pamphlet proclaiming this "new guild of craftsmen, without the class snobbery", described "painting and sculpture rising to heaven out of the hands of a million craftsmen, the crystal symbol of the new faith of the future." By 1923, however, Gropius was no longer evoking images of soaring Romanesque cathedrals and the craft-driven aesthetic of the " Völkisch movement", instead declaring "we want an architecture adapted to our world of machines, radios and fast cars." Gropius argued that a new period of history had begun with the end of the war. He wanted to create a new architectural style to reflect this new era. His style in architecture and consumer goods was to be functional, cheap and consistent with mass production. To these ends, Gropius wanted to reunite art and craft to arrive at high-end functional products with artistic merit. The Bauhaus issued a magazine called and a series of books called "Bauhausbücher". Since the Weimar Republic lacked the number of raw materials available to the United States and Great Britain, it had to rely on the proficiency of a skilled labour force and an ability to export innovative and high-quality goods. Therefore, designers were needed and so was a new type of art education. The school's philosophy stated that the artist should be trained to work with the industry.

Weimar was in the German state of Thuringia, and the Bauhaus school received state support from the Social Democrat-controlled Thuringian state government. The school in Weimar experienced political pressure from conservative circles in Thuringian politics, increasingly so after 1923 as political tension rose. One condition placed on the Bauhaus in this new political environment was the exhibition of work undertaken at the school. This condition was met in 1923 with the Bauhaus' exhibition of the experimental Haus am Horn. The Ministry of Education placed the staff on six-month contracts and cut the school's funding in half. The Bauhaus issued a press release on 26 December 1924, setting the closure of the school for the end of March 1925. At this point it had already been looking for alternative sources of funding. After the Bauhaus moved to Dessau, a school of industrial design with teachers and staff less antagonistic to the conservative political regime remained in Weimar. This school was eventually known as the Technical University of Architecture and Civil Engineering, and in 1996 changed its name to Bauhaus-University Weimar.

The Bauhaus moved to Dessau in 1925 and new facilities there were inaugurated in late 1926. Gropius's design for the Dessau facilities was a return to the futuristic Gropius of 1914 that had more in common with the International style lines of the Fagus Factory than the stripped down Neo-classical of the Werkbund pavilion or the Sommerfeld House. During the Dessau years, there was a remarkable change in direction for the school. According to Elaine Hoffman, Gropius had approached the Dutch architect Mart Stam to run the newly founded architecture program, and when Stam declined the position, Gropius turned to Stam's friend and colleague in the ABC group, Hannes Meyer.

Meyer became director when Gropius resigned in February 1928, and brought the Bauhaus its two most significant building commissions, both of which still exist: five apartment buildings in the city of Dessau, and the Bundesschule des Allgemeinen Deutschen Gewerkschaftsbundes (ADGB Trade Union School) in Bernau bei Berlin. Meyer favoured measurements and calculations in his presentations to clients, along with the use of off-the-shelf architectural components to reduce costs. This approach proved attractive to potential clients. The school turned its first profit under his leadership in 1929.

But Meyer also generated a great deal of conflict. As a radical functionalist, he had no patience with the aesthetic program and forced the resignations of Herbert Bayer, Marcel Breuer, and other long-time instructors. Even though Meyer shifted the orientation of the school further to the left than it had been under Gropius, he didn't want the school to become a tool of left-wing party politics. He prevented the formation of a student communist cell, and in the increasingly dangerous political atmosphere, this became a threat to the existence of the Dessau school. Dessau mayor Fritz Hesse fired him in the summer of 1930. The Dessau city council attempted to convince Gropius to return as head of the school, but Gropius instead suggested Ludwig Mies van der Rohe. Mies was appointed in 1930 and immediately interviewed each student, dismissing those that he deemed uncommitted. He halted the school's manufacture of goods so that the school could focus on teaching, and appointed no new faculty other than his close confidant Lilly Reich. By 1931, the Nazi Party was becoming more influential in German politics. When it gained control of the Dessau city council, it moved to close the school.

In late 1932, Mies rented a derelict factory in Berlin (Birkbusch Street 49) to use as the new Bauhaus with his own money. The students and faculty rehabilitated the building, painting the interior white. The school operated for ten months without further interference from the Nazi Party. In 1933, the Gestapo closed down the Berlin school. Mies protested the decision, eventually speaking to the head of the Gestapo, who agreed to allow the school to re-open. However, shortly after receiving a letter permitting the opening of the Bauhaus, Mies and the other faculty agreed to voluntarily shut down the school.[when? ]

Although neither the Nazi Party nor Adolf Hitler had a cohesive architectural policy before they came to power in 1933, Nazi writers like Wilhelm Frick and Alfred Rosenberg had already labelled the Bauhaus "un-German" and criticized its modernist styles, deliberately generating public controversy over issues like flat roofs. Increasingly through the early 1930s, they characterized the Bauhaus as a front for communists and social liberals. Indeed, when Meyer was fired in 1930, a number of communist students loyal to him moved to the Soviet Union.

Even before the Nazis came to power, political pressure on Bauhaus had increased. The Nazi movement, from nearly the start, denounced the Bauhaus for its " degenerate art", and the Nazi regime was determined to crack down on what it saw as the foreign, probably Jewish, influences of "cosmopolitan modernism". Despite Gropius's protestations that as a war veteran and a patriot his work had no subversive political intent, the Berlin Bauhaus was pressured to close in April 1933. Emigrants did succeed, however, in spreading the concepts of the Bauhaus to other countries, including the "New Bauhaus" of Chicago: Mies decided to emigrate to the United States for the directorship of the School of Architecture at the Armour Institute (now Illinois Institute of Technology) in Chicago and to seek building commissions. The simple engineering-oriented functionalism of stripped-down modernism, however, did lead to some Bauhaus influences living on in Nazi Germany. When Hitler's chief engineer, Fritz Todt, began opening the new autobahns (highways) in 1935, many of the bridges and service stations were "bold examples of modernism", and among those submitting designs was Mies van der Rohe.

The paradox of the early Bauhaus was that, although its manifesto proclaimed that the aim of all creative activity was building, the school did not offer classes in architecture until 1927. During the years under Gropius (1919-1927), he and his partner Adolf Meyer observed no real distinction between the output of his architectural office and the school. So the built output of Bauhaus architecture in these years is the output of Gropius: the Sommerfeld house in Berlin, the Otte house in Berlin, the Auerbach house in Jena, and the competition design for the Chicago Tribune Tower, which brought the school much attention. The definitive 1926 Bauhaus building in Dessau is also attributed to Gropius. Apart from contributions to the 1923 Haus am Horn, student architectural work amounted to un-built projects, interior finishes, and craft work like cabinets, chairs and pottery.

In the next two years under Meyer, the architectural focus shifted away from aesthetics and towards functionality. There were major commissions: one from the city of Dessau for five tightly designed "Laubenganghäuser" (apartment buildings with balcony access), which are still in use today, and another for the Bundesschule des Allgemeinen Deutschen Gewerkschaftsbundes (ADGB Trade Union School) in Bernau bei Berlin. Meyer's approach was to research users' needs and scientifically develop the design solution.

Mies van der Rohe repudiated Meyer's politics, his supporters, and his architectural approach. As opposed to Gropius's "study of essentials", and Meyer's research into user requirements, Mies advocated a "spatial implementation of intellectual decisions", which effectively meant an adoption of his own aesthetics. Neither Mies van der Rohe nor his Bauhaus students saw any projects built during the 1930s.

The popular conception of the Bauhaus as the source of extensive Weimar-era working housing is not accurate. Two projects, the apartment building project in Dessau and the Törten row housing also in Dessau, fall in that category, but developing worker housing was not the first priority of Gropius nor Mies. It was the Bauhaus contemporaries Bruno Taut, Hans Poelzig and particularly Ernst May, as the city architects of Berlin, Dresden and Frankfurt respectively, who are rightfully credited with the thousands of socially progressive housing units built in Weimar Germany. The housing Taut built in south-west Berlin during the 1920s, close to the U-Bahn stop Onkel Toms Hütte, is still occupied.

The Bauhaus had a major impact on art and architecture trends in Western Europe, Canada, the United States and Israel in the decades following its demise, as many of the artists involved fled, or were exiled by the Nazi regime. In 1996, four of the major sites associated with Bauhaus in Germany were inscribed on the UNESCO World Heritage List (with two more added in 2017).

In 1928, the Hungarian painter Alexander Bortnyik founded a school of design in Budapest called Műhely, which means "the studio". Located on the seventh floor of a house on Nagymezo Street, it was meant to be the Hungarian equivalent to the Bauhaus. The literature sometimes refers to it-in an oversimplified manner-as "the Budapest Bauhaus". Bortnyik was a great admirer of László Moholy-Nagy and had met Walter Gropius in Weimar between 1923 and 1925. Moholy-Nagy himself taught at the Miihely. Victor Vasarely, a pioneer of op art, studied at this school before establishing in Paris in 1930.

Walter Gropius, Marcel Breuer, and Moholy-Nagy re-assembled in Britain during the mid-1930s and lived and worked in the Isokon housing development in Lawn Road in London before the war caught up with them. Gropius and Breuer went on to teach at the Harvard Graduate School of Design and worked together before their professional split. Their collaboration produced, among other projects, the Aluminum City Terrace in New Kensington, Pennsylvania and the Alan I W Frank House in Pittsburg. The Harvard School was enormously influential in America in the late 1920s and early 1930s, producing such students as Philip Johnson, I. M. Pei, Lawrence Halprin and Paul Rudolph, among many others.

In the late 1930s, Mies van der Rohe re-settled in Chicago, enjoyed the sponsorship of the influential Philip Johnson, and became one of the world's pre-eminent architects. Moholy-Nagy also went to Chicago and founded the New Bauhaus school under the sponsorship of industrialist and philanthropist Walter Paepcke. This school became the Institute of Design, part of the Illinois Institute of Technology. Printmaker and painter Werner Drewes was also largely responsible for bringing the Bauhaus aesthetic to America and taught at both Columbia University and Washington University in St. Louis. Herbert Bayer, sponsored by Paepcke, moved to Aspen, Colorado in support of Paepcke's Aspen projects at the Aspen Institute. In 1953, Max Bill, together with Inge Aicher-Scholl and Otl Aicher, founded the Ulm School of Design (German: Hochschule für Gestaltung - HfG Ulm) in Ulm, Germany, a design school in the tradition of the Bauhaus. The school is notable for its inclusion of semiotics as a field of study. The school closed in 1968, but the "Ulm Model" concept continues to influence international design education. Another series of projects at the school were the Bauhaus typefaces, mostly realized in the decades afterward.

The influence of the Bauhaus on design education was significant. One of the main objectives of the Bauhaus was to unify art, craft, and technology, and this approach was incorporated into the curriculum of the Bauhaus. The structure of the Bauhaus Vorkurs (preliminary course) reflected a pragmatic approach to integrating theory and application. In their first year, students learnt the basic elements and principles of design and colour theory, and experimented with a range of materials and processes. This approach to design education became a common feature of architectural and design school in many countries. For example, the Shillito Design School in Sydney stands as a unique link between Australia and the Bauhaus. The colour and design syllabus of the Shillito Design School was firmly underpinned by the theories and ideologies of the Bauhaus. Its first year foundational course mimicked the Vorkurs and focused on the elements and principles of design plus colour theory and application. The founder of the school, Phyllis Shillito, which opened in 1962 and closed in 1980, firmly believed that "A student who has mastered the basic principles of design, can design anything from a dress to a kitchen stove". In Britain, largely under the influence of painter and teacher William Johnstone, Basic Design, a Bauhaus-influenced art foundation course, was introduced at Camberwell School of Art and the Central School of Art and Design, whence it spread to all art schools in the country, becoming universal by the early 1960s.

One of the most important contributions of the Bauhaus is in the field of modern furniture design. The characteristic Cantilever chair and Wassily Chair designed by Marcel Breuer are two examples. (Breuer eventually lost a legal battle in Germany with Dutch architect/designer Mart Stam over patent rights to the cantilever chair design. Although Stam had worked on the design of the Bauhaus's 1923 exhibit in Weimar, and guest-lectured at the Bauhaus later in the 1920s, he was not formally associated with the school, and he and Breuer had worked independently on the cantilever concept, leading to the patent dispute.) The most profitable product of the Bauhaus was its wallpaper.

The physical plant at Dessau survived World War II and was operated as a design school with some architectural facilities by the German Democratic Republic. This included live stage productions in the Bauhaus theater under the name of Bauhausbühne ("Bauhaus Stage"). After German reunification, a reorganized school continued in the same building, with no essential continuity with the Bauhaus under Gropius in the early 1920s. In 1979 Bauhaus-Dessau College started to organize postgraduate programs with participants from all over the world. This effort has been supported by the Bauhaus-Dessau Foundation which was founded in 1974 as a public institution.

Later evaluation of the Bauhaus design credo was critical of its flawed recognition of the human element, an acknowledgment of "the dated, unattractive aspects of the Bauhaus as a projection of utopia marked by mechanistic views of human nature...Home hygiene without home atmosphere."

Subsequent examples which have continued the philosophy of the Bauhaus include Black Mountain College, Hochschule für Gestaltung in Ulm and Domaine de Boisbuchet.

The White City ( Hebrew: העיר הלבנה‎, refers to a collection of over 4,000 buildings built in the Bauhaus or International Style in Tel Aviv from the 1930s by German Jewish architects who emigrated to the British Mandate of Palestine after the rise of the Nazis. Tel Aviv has the largest number of buildings in the Bauhaus/International Style of any city in the world. Preservation, documentation, and exhibitions have brought attention to Tel Aviv's collection of 1930s architecture. In 2003, the United Nations Educational, Scientific and Cultural Organization ( UNESCO) proclaimed Tel Aviv's White City a World Cultural Heritage site, as "an outstanding example of new town planning and architecture in the early 20th century." The citation recognized the unique adaptation of modern international architectural trends to the cultural, climatic, and local traditions of the city. Bauhaus Center Tel Aviv organizes regular architectural tours of the city.

Centenary year, 2019

As the centenary of the founding of Bauhaus, several events, festivals, and exhibitions were held around the world in 2019. The international opening festival at the Berlin Academy of the Arts from 16 to 24 January concentrated on "the presentation and production of pieces by contemporary artists, in which the aesthetic issues and experimental configurations of the Bauhaus artists continue to be inspiringly contagious". Original Bauhaus, The Centenary Exhibition at the Berlinische Galerie (6 September 2019 to 27 January 2020) presented 1,000 original artefacts from the Bauhaus-Archiv's collection and recounted the history behind the objects.

In September 2020, President of the European Commission Ursula Von der Leyen introduced the New European Bauhaus (NEB) initiative during her State of the Union address. The NEB is a creative and interdisciplinary movement that connects the European Green Deal to everyday life. It is a platform for experimentation aiming to unite citizens, experts, businesses and institutions in imagining and designing a sustainable, aesthetic and inclusive future.

Sport and physical activity were an essential part of the original Bauhaus approach. Hannes Meyer, the second director of Bauhaus Dessau, ensured that one day a week was solely devoted to sport and gymnastics. 1 In 1930, Meyer employed two physical education teachers. The Bauhaus school even applied for public funds to enhance its playing field. The inclusion of sport and physical activity in the Bauhaus curriculum had various purposes. First, as Meyer put it, sport combatted a "one-sided emphasis on brainwork." In addition, Bauhaus instructors believed that students could better express themselves if they actively experienced the space, rhythms and movements of the body. The Bauhaus approach also considered physical activity an important contributor to wellbeing and community spirit. Sport and physical activity were essential to the interdisciplinary Bauhaus movement that developed revolutionary ideas and continues to shape our environments today.

People who were educated, or who taught or worked in other capacities, at the Bauhaus.

The closure, and the response of Mies van der Rohe, is fully documented in Elaine Hochman's Architects of Fortune.

Google honored Bauhaus for its 100th anniversary on 12 April 2019 with a Google Doodle.

1. ^ Oxford Dictionary of Art and Artists (Oxford: Oxford University Press, 4th edn., 2009), ISBN 0-19-953294-X, pp. 64-66

2. ^ Routledge international handbook of participatory design. Jesper Simonsen, Toni Robertson. New York: Routledge. 2013. p. 38. ISBN 978-0-415-69440-7. OCLC 754734489.

3. (in Russian) Great Soviet Encyclopedia; Bolshaya Sovetskaya Entsiklopediya, Вхутемас

4. Wood, Paul (1999) ^ The Challenge of the Avant-Garde. New Haven: Yale University Press ISBN 0-300-07762-9, p. 244

5. ^ Colton, Timothy J. (1995) Moscow: Governing the Socialist Metropolis. Cambridge MA: Harvard University Press ISBN 0-674-58749-9; p. 215

6. ^ Whitford, Frank, ed. (1992). The Bauhaus: Masters & Students by Themselves. London: Conran Octopus. p. 32. ISBN 978-1-85029-415-3. He invented the name 'Bauhaus' not only because it specifically referred to Bauen ('building', 'construction')-but also because of its similarity to the word Bauhütte, the medieval guild of builders and stonemasons out of which Freemasonry sprang. The Bauhaus was to be a kind of modern Bauhütte, therefore, in which craftsmen would work on common projects together, the greatest of which would be buildings in which the arts and crafts would be combined.

7. Hal Foster, ed. (2004). "1923: The Bauhaus ... holds its first public exhibition in Weimar, Germany". Art Since 1900: Volume 1 - 1900 to 1944. Rosalind Krauss, Yve-Alain Bois, Benjamin Buchloh. New York: Thames & Hudson. pp. 185-189. ISBN 978-0-500-28534-3.

8. Michael Baumgartner and Josef Helfenstein ^ At the Bauhaus in Weimar, 1921-1924 Archived 29 September 2009 at the Wayback Machine, at Zentrum Paul Klee

9. ^ Richard A. Etlin (2002). Art, culture, and media under the Third Reich. University of Chicago Press. p. 291. ISBN 978-0-226-22086-4.

10. ^ Gropius, Walter (April 1919). "Manifesto of the Staatliches Bauhaus". BauhausManifesto.com.

11. Gaston Diehl, Vasarely, New York: Crown, 1972, p. 12

12. See: William Chapin Seitz, Marla Price, ^ Art in the Age of Aquarius, Smithsonian Inst Press, 1992, p. 92; Edward Lucie-Smith, Late Modern: The Visual Arts Since 1945, London: Thames & Hudson, 1976, p. 164; Jean Louis Ferrier, Yann Le Pichon, Art of our century: the story of western art, 1900 to the present 1990, London : Longman, p. 521.

13. ^ Ulm, Ulmer Museum/HfG-Archiv. "HfG-Archiv Ulm - The HfG Ulm". www.hfg-archiv.ulm.de. Archived from the original on 4 October 2008.

14. ^ "UNESCO, Decision Text, World Heritage Centre, retrieved 14 September 2009".

15. Weber, Micholas Fox, ^ The Bauhaus at 100: science by design, Nature, 6 August 2019 (with pdf link)

16. ^ "Bauhaus in pictures: The architects exiled by Nazis". BBC News. 16 January 2019. Archived from the original on 16 January 2019.

17. ^ "Original Bauhaus, The Centenary Exhibition". Berlinische Galerie. 6 September 2019.

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The ( Staatliches Bauhaus ( German: [ˈʃtaːtlɪçəs ˈbaʊˌhaʊs] Bauhaus ( listen )), commonly known as the German for 'building house'), was a German art school operational from 1919 to 1933 that combined crafts and the fine arts.[1] The school became famous for its approach to design, which attempted to unify individual artistic vision with the principles of mass production and emphasis on function.[1] The Bauhaus was founded by architect Walter Gropius in Weimar.

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I know how much dry glass forming material is in the big base batch (3,000g). I know the total weight of all the material in the base glaze (6,825g). I know the weight of the smaller portioned out glaze batches (100g). Now I just have to solve for X (which is the amount of dry glass forming material in the small portions).

I solve for X using cross-multiplication.

3,000g X 100g / 6,825g = 43.96g
X= 43.96g

X=43.96g. This is the weight I will use to calculate the correct percentage of colorant to add to each 100g wet batch. I am testing 5% additions of stains in this glaze.

So 43.96g x 5% = 2.198g stain added to each 100g wet batch. I use a scale that measures two decimal points for greater accuracy. Measuring out each stain at 2.18g - 2.20g. Weigh the colorants in a separate container then add them to the wet glaze.

To mix all these separate little containers of glaze/colorants thoroughly and quickly, I use a milk frother wand. This allows me to mix the colorants into each little batch in a matter of a few seconds, with no additional sieving necessary. The battery powered milk frother is fine if your only going to test a few batches every so often. But if you are really into colorant / glaze testing I recommend cutting off the frother part and using it in a Dremel. I use the lowest setting on the Dremel, around 5,000 rpm, any more than this and the frother head will start to wobble and your glaze will go flying out of the container. NOTE! These milk frother wands are not meant for these kinds of rpms, it works but be safe and aware of the tool. Also if you're going to use a Dremel, make sure you get a milk frother that has the "squirrel cage" type frothing head(like in pic 4). It is centered and doesn't vibrate at the higher rpms like the other kinds do.

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Best Practice Glaze Testing - Rat City Studios

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My Introduction To Glaze Testing

I find ceramic glazes to be absolutely fascinating. I had no idea when I started working with clay that glazes would become the main focus of my life.

My first year of pottery school was mainly about learning how clay worked and different ways of making different shapes. The focus was on form, function and skill-building, not so much on colour and aesthetics just yet.

Glazing was always an afterthought and I basically ruined most of my pieces by glazing them. In first year, we didn't make our own glazes, we just used the studio glazes that were provided.

I didn't have a clue what glazes were made of, how they were made or what happened to them in the kiln. And to be honest, I wasn't all that interested. I just wanted to finally make something that looked how I imagined it should.

I was trying to be an artist. Somehow I ended up in art school which is the last place I would have imagined myself a few years prior. But life is funny like that.

Then came first semester of my second year. My very first glaze technology class. This was a major turning point in my life.

We finally learned to make glazes ourselves. We made a LOT of glazes ourselves. Collectively as a group, we made close to 1500 glaze tests. And this is when I really fell in love with ceramics.

First of all, wearing a respirator and weighing out powders using a triple beam balance scale made me feel super cool, like a scientist.

Yeah, I think scientists are cool!

The systematic testing that we did gave the right side of my brain a little break and lit up the left side of my brain that loves systems and calculations and data.

Math and chemistry were my best subjects in high school and even though I didn't understand the chemistry of glazes yet, I felt like I was being taken back to my roots. Glaze testing felt really natural and I finally understood why someone like me ended up in art school.

That semester blew my mind. As a class, we first tested 128 different base recipes with multiple variations of each.

Then we each chose 2 base recipes and did "colour runs" with 45 different colourant tests for each base recipe.
One base recipe, 45 different colourant tests
Then, we each chose 9 colourant tests that we liked from each base and made these "glaze triangles" where we blended each glaze1:1 with every other glaze, resulting in 45 more glaze colours per base.
Colourant tests blended together
We had a lot of glaze cups and a lot of test tiles!

After taking that class, I was hooked on glaze testing. I loved trying new recipes and adding and removing ingredients to see what would happen. I would do lots of mini colour runs, testing just a few colourants with a base recipe to see how they reacted and whether I wanted to explore further.

I took lots of notes and photographs and spent countless hours staring at test tiles and recipes and coming up with new things I wanted to try.

I got to the point where I was more excited about test tiles coming out of the kiln than my own pottery. I made pots just to put glazes on them. And now, 10 years later, with thousands of tests behind me, I'm still just as curious and excited about glazes as ever.

The #1 Habit That Will Deepen Your Understanding of Glazes

After leaving school and putting together my home studio, I no longer had the luxury of glaze firings happening every few days. My glaze firings were often several weeks apart since I was making pots part-time and I was the only person filling my kiln.

Since my glaze firings weren't very often, I made it a habit to put at least one test into every single glaze firing.

I didn't want a glaze firing to go by without getting new information. I needed to seize each and every opportunity to try something new and see the results. Seeing results are the only way to learn and move forward.

This one little habit, multiplied by years of glaze firings has led to a much deeper understanding of how glaze materials work.
My #1 Habit: PUT A TEST IN EVERY GLAZE FIRING
We potters are so lucky that we can create our own glazes from scratch and have an infinite number of surface possibilities to choose from. The only thing that gets in our way is a lack of understanding of how our materials work and how to solve the problems that arise.

Developing a regular glaze testing habit is going to bring you closer to that deeper level of understanding with every firing.

I would love it if my story inspires you to make glaze testing a habit in your studio as well. I have some tips and ideas for you to get started down the glaze testing rabbit hole.

15 Tips to Get Started With Glaze Testing

If you're like me and are fascinated by how glazes work, or you just want to understand glazes better so you can create unique surfaces for your pottery, here are some tips that will help you deepen your relationship with glazes and expand your palette.
1. Make lots of test tiles.
Make so many test tiles that you don't think twice about using them. Test tiles can be any shape or size that you wish. They can be extruded, rolled as a slab, squished, thrown on the wheel, smooth, textured, you name it. It doesn't matter how you make them, it just matters that you have them available and that you use them.
These are just some of the glaze tests I've done over the years 2. Make test tiles of every clay body that you use regularly.
Glazes will appear different and react differently to different clay bodies. When you're testing a glaze, test it on multiple clay bodies if you can.
Testing colourants on 3 different clay bodies 3. Make test pots.
Test tiles tend to be small and only give a certain amount of information. It can be disappointing to find a glaze that you like on a little test tile and then glaze a whole piece with it and it looks completely different. I recommend making a bunch of test pots so you can see how glazes pool and run down vertical surfaces, etc.

To make test pots, choose a method that's really fast so you can make lots and you're not worried about wasting them. Make little bowls or cups or extruded cylinders. Test pots are great for filling in the spaces between other pots in your glaze firings.
I make lots of these small dishes and use them to test runny glazes 4. Buy some glaze testing cups with lids.
You can buy a sleeve of plastic drink cups, or I like to use small, clear plastic deli containers. They have flat lids so they can easily be stacked and stored.
I prefer the containers on the right over the cups on the left because they're stackable 5. Test your current glazes at different thicknesses.
A good way to get started glaze testing is to take the glazes that you're already using and try 1 second, 3 second, 6 second and 10 second dips, each on a separate test tile. Label them accordingly and fire them. You may get some interesting results with different thicknesses, depending on the glaze.

Make sure your glazes are mixed really well before dipping, and your kiln shelves are well protected in case your glaze runs.
Same glaze, different thicknesses 6. When dipping test tiles, make it a habit to always submerge the tile for the same amount of time.
For example, I always do a 6-second dip for test tiles. If I do more or less I'll write it on the test tile for reference. This helps for consistency of results. The reason I do 6 seconds, which I consider long for dipping, is because a small test tile generally won't absorb as much glaze as a large piece would. I want the test tile to be somewhat of an accurate representation of how the glaze would look on a piece.
7. Take a glaze recipe that you like, remove the colourant and test the base recipe on its own.
This will help you really see the glaze at its core, without being aesthetically influenced by its colour. Is it glossy or matte? Is it rough or smooth? Is it opaque or transparent? Does it have flecks and variation or is it uniform? Does it craze or not? Does it run or is it stable?

Then you can compare the base to how it looks with colourants and see how the colourant has affected the melt and surface texture. Colourants can change more than just the colour.

If you're not sure which are the colourants, they're typically copper, cobalt, iron, chrome, manganese, nickel, rutile, titanium, zircopax, tin and mason stains.

Same glaze, with and without colourants 8. Test the base recipe from tip #7 with different colourants.
Examples of colourants you could try are:

There are more colourants, but those are the most common for when you're just getting started.
Same glaze with different colourants 9. When you make a test glaze batch, make at least 200g
You can go smaller but smaller batches will be less accurate unless you have a scale that measures less than 1g increments (readability). If you have a scale with a readability of 0.1g or less then go ahead and make smaller batches. If the smallest measurement your scale will weigh is 1g, then you'll get more accurate results with 200g batches.

Making 200g also gives you enough glaze to submerge your test tiles without hitting the bottom of the cup.

Of these three scales, the triple beam in the middle is the only one that will weigh less than 1 gram 10. If you want to test a few different colourants in one base, make a large batch of the base and then divide it into smaller test cups before adding colourants.
For example, if you want to test 5 different colourants, make 1000g of the base, mix and sieve the glaze and then divide it equally into 5 different test cups. This will give you approximately 200g of the base materials in each test cup. Then add the colourants as percentages of 200g.
I made 900g of the base and split it evenly into six cups of 150g each Then I added different colourants to each cup 11. After you've tested different colourants in a base recipe, try blending them together.
This will give you new colours. For example, you could take a test containing 2% copper and mix it with a test containing 1% cobalt. As long as the batch sizes are equal, the resulting glaze will have 1% copper and 0.5% cobalt. You can find some gems this way.
12. PUT A GLAZE TEST IN EVERY FIRING
This is the #1 habit that will lead to a deeper understanding of your glazes.
13. Don't forget to use witness cones in all your glaze firings.
You'd be surprised at what a difference a higher or lower temperature firing will make on your glaze results.
An example of a cone pack. I put at least one of these in every firing. 14. Take lots of notes and photos of your process and results.
Keep a glaze testing journal. Write everything down. You never know when the smallest detail can make a big difference. When you keep track of it all, you will start to connect the dots on which factors are influencing your results.
15. Have fun, experiment, be creative, try new things, follow your curiosity, enjoy the process.
Glaze testing makes unloading the kiln even more exciting. There's something about coming up with a test you want to try, making it and then seeing the results that feels so empowering.

If you see glaze testing as a chore, you're probably not going to do it very much. But if you see it as an exciting way to add a new level of creativity to the ceramics process, you'll probably make some interesting discoveries.
Me in my respirator. Safety first!
I hope this post gave you some ideas for tests you can try. This is a very broad overview of ways to test glazes. If you have any questions or want me to go deeper on one of the tips, let me know in the comments.

No knowledge of chemistry is required to do this type of glaze testing. Once you're hooked on glaze testing, there's a whole wide world of chemistry to explore. The depth of knowledge you can reach is endless. I hope you'll join me on the journey.

Do you already love glaze testing? What are some of your favourite tests or tips to share? Let me know in the comments. Do you have any kiln sitter tips to share? Please leave a comment below.

If this post helped or inspired you, please share it with others.

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15 Tips to Get Started with Glaze Testing - Sue McLeod Ceramics

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I find ceramic glazes to be absolutely fascinating. I had no idea when I started working with clay that glazes would become the main focus of my life. Glazing was always an afterthought and I basically ruined most of my pieces by glazing them...

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You can see a collection of recipes here, but the recurring elements are:

High Boron (0.3-0.4)

High AM Flux (generally 0.4:0.6 - 0.5:0.5)

Reasonably high silica and alumina

Colourants are Rutile, Iron, and Cobalt

For my Ceramic Materials Workshop Advancing Glazes class I wanted to test which of those factors could be changed while keeping the effect. From what I knew of glazes, my guess was that the most relevant would be the boron and the rutile. Those of you who have done any of the CMW classes will probably know that there are a few ways to achieve phase separation (literally where the glaze separates to form different compositions within the glaze), and those are two of the main ones. Also, the boron will increase the fluidity and the rutile will add some opacity.

Fluxes

So my first test was to take my usual Floating Blue, keeping everything else the same (boron, silica, alumina, colourants), and change the flux ratio to 0.3:0.7. Rather than keep the AE fluxes in exactly the same proportions while I did this, I did three versions. One had only calcium added (the Gerstley Borate contributes most of the AE fluxes anyway), one had only magnesium added, and the third had only strontium. I then did a blend between the calcium and each of the other two:

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Understanding Floating Blues - Old Forge Creations

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Most of my glaze combinations use a Floating Blue for at least part of the application. They're one of the most variable glazes I've ever used, as they're fluid enough to flow and mix with other glazes.

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Cake Slice Box

A piece of cake. Quite literally. A wedge-shaped box that can be used to store pieces of cake.

The box consists of an upper and a lower part. The upper part is the cover. The lower part, the tray, does not need glue because it will be locked by the cover.

By default, the cover is 5% larger then the tray but this can be adjusted in the expert settings.

The angle is a measure for how big a piece of cake can fit in. Look in the figure if you don't know what to enter here. For example, an angle of 30º is large enough for 1 piece from a 12-piece cake. The length is the length of the piece, which should be about half the diameter of the complete cake. But, be sure to add quite some allowance here.

Heart Shaped Box

The measurements are different to standard boxes because of the way the heart is modelled. It is made from an ellipse, which is rotated, cut in half vertically and then mirrored.

The "Length" measures between the two sharp corners of the heart. The width is calculated by the program to match the rotation (tilt) and shape of the ellipse. (Think of the shape as the "Body Mass Index" of the heart).

The box consists of a base and a lid. Each part has two heart shaped "caps": the smallest one goes on the inside, the larger one goes on the outside to conceal the ugly-looking glue flaps. It's easiest to glue the heart-shaped caps instead of the glue flaps. The "Paper Thickness" parameter is only used for making the outside hearts larger then the inside.

Nestable Tray

A basic tray with glued sides and a draft angle. Use 0º if you want a straight sides, but use a larger value if you want trays that can be stacked into eachother.

The length and width are measured at the top, so when you use a non-zero draft angle, the dimensions at the bottom will be smaller.

Because of the draft angle, the trays can be nested. This makes this model ideal as an organizer for storing small items. LEGO®, for example.

If you choose a too large value for the draft angle or a too small value for the height, the draft angle will be adjusted.

Passepartout

Passepartout, Photo Frame or Shadow Box. Glue-less, hollow, double-walled tray.Can also be used as box insert.

Create a photo frame for your photo's with a posh, wide frame.

Enter the dimension of the "inner space" (the size of the picture or object to display), together with how thick and wide you'd like the border of the frame to be. The final model will be larger, because of the width of border of the frame. The model can be constructed without using glue, although a bit of glue won't hurt.

When used as an insert, you might not need the inner part.

For assembly instructions, have a look at the YouTube-movie

Polygonal Box

Tube-shaped (or prismatic), polygonal box with gusseted, integrated lid.

This box is very decorative and ideal for gift wrapping odd-shaped presents. The lid uses both mountain and valley folds. The glue tabs on the bottom fit together precisely. The lid will fold easier if you remove some material from the place where the five fold lines meet.

The model does not work for 3 or less sides

Pyramid Box

A box in the shape of a pyramid. The base of the shapes functions as the lid, so to open it, you would hold it downside up.

The default values yield a pyramid in the same ratio as the Cheops pyramid.

The Platonic Solids

Models of all five so-called Platonic Solids. The Platonic Solids are the five regular convex polyhedra.

The Cube is the most famous one, of course, although he likes to be called "hexahedron" among friends. Also the other platonic solids are named after the number of faces (or hedra) they have. I.e. Tetrahedron, Octahedron,Dodecahedron, Icosahedron. (Now you know how to count in classical Greek, too!)

There is only parameter：the diameter of the midsphere. The midsphere is the sphere from the center of the object that touches all the edges exactly in middle.

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A piece of cake. Quite literally. A wedge-shaped box that can be used to store pieces of cake. The box consists of an upper and a lower part. The upper part is the cover. The lower part, the tray, does not need glue because it will be locked by the cover.

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5 Tips for Making the Most of Ceramic Glaze Testing Greg Daly shares test tile tips! Greg Daly

Search the Daily

Published Jan 20, 2021

The best way to learn about ceramic glazes and glaze materials is to test them. By studying what happens when varying amounts of various ingredients are combined in a glaze and then fired to various temperatures, you start to understand how materials affect each other, and therefore how to troubleshoot when your results are not what you wanted. But it can be intimidating to delve into glaze chemistry. It is fairly complex. It includes the word ‘chemistry’ in its name. To some—me included—that is an immediate red flag. So in today's post, Greg Daly gives five excellent tips for getting the most out of glaze testing. Read on, and then get out there and test! - Jennifer Poellot Harnetty, editor.

Figure 1.1. Greg Daly, bowl, 1986. Glazed with potash feldspar, poured, with iron brushwork. Photo: Stewart Hay.

1. Be thorough in your recording of materials, tests and firings. Without a reference to what was in a test firing, all you are left with is a glazed tile, with no information to enable you to explore it further. 2. Closely observe the fired tests; in the firing, many important pieces of information are often overlooked. Don't throw out a test for at least a month, or even up to a year. The test result may not be what you are looking for at the time, but it may turn out to be just right later on. Even sitting with the tests in full natural light, you may see something of interest, right at the edge of a glaze where it thins out. Don't keep tests locked away; I put them on windowsills, on a desk, anywhere I will constantly see them, and I swap them periodically.
3. Keep an open mind at all times. We can develop such tight concepts of what a glazeis and should do that we miss the big picture, as well as the immediate evidence of what we are holding in our hands. As a student researching copper-red glazes, I had a firm idea of what they should look like in color, tone and surface - an ox blood or peach bloom  - having seen them depicted in books. But I was liberated when seeing copper-red glazes en masse at the Victoria & Albert Museum: in a room full of copper reds, the colors were qualitatively different from each other in shade, intensity, surface depth and color. This freed me of my expectations of how a glaze should look. Glazes have families - copper reds, iron, luster glazes, shino, etc. -  but within any family there is also diversity.

Develop! your own glazes!

There's nothing more satisfying than putting one of your own glazes on a pot you made — and it's not that hard to do! All you need is a little information about what different raw materials do, how much of each to add, and VOILA! Developing Glazes can get you on your way! Learn more and download an excerpt!

glaze testing

4. Be playful. If it occurs to you to try one material with another, and others say it will not work, do it anyway. You will always learn and extend your understanding. In Chapter 3 [of Developing Glazes] I have outlined a way of testing materials for fun, called "random glazes." Taking any four materials and any four numbers between 5 and 55, you will find you have a workable surface at cones 8 to 10. I have repeated this countless times in workshops. Many potters dismiss this odd way of creating a glaze, but are then surprised when they see the results.
5. Have a quick way of testing. Testing is what puts most people off, so they turn to the last page for recipes (the answers). But when you simplify the process and results come back, there is nothing more rewarding. Systems for ease of testing are covered in Chapter 3 of Greg Daly's Developing Glazes.

**First published in 2014.

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5 Tips for Making the Most of Ceramic Glaze Testing

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Glaze chemistry is fairly complex, which to some is an immediate red flag. So Greg Daly gives five excellent tips for getting the most out of glaze testing.

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Every business needs to have some bookkeeping, and the business of glaze development is really no different. Records are for your own benefit and should be kept as simple as possible.

Recording Glaze Development

It’s amazing how many students and full-time clay workers go about making glazes with a lengthy and time-consuming process, only to forget to clearly write down just what they’ve done. It seems to be quite normal to work with scraps of paper and the odd hieroglyphic on the back or base of the test tile. I know from bitter experience that the finest glaze ever developed was, of course, the one where the scrap of paper got lost or the hieroglyphic got obliterated by an accident of firing, if any record was made at all. Somehow, that one gem that might have been a crowning glory was lost forever. I’m sure this has happened to every potter at some time, but it doesn’t have to. It’s very easy to start in the glaze-making process with good working habits such as:

1. Keep an accurate notebook.

2. Develop a serial numbering system.

3. Work as neatly as possible.

4. Write down everything in your notebook.

5. Take basic health precautions when handling materials.

1. An accurate notebook is very important and can be set up in many ways. It’s best to get a hardback book simply because these have a greater longevity in the wear and tear of studio life. The book can be sectioned for glaze development at various temperatures. It can also be vertically lined for tabulation of procedures followed, as in the accompanying illustration. Starting with this or a similar format, it’s easy to keep records.

2

2. Developing a serial numbering system or code is quite simple, and if you use a combination of letters and numbers, it is easy to follow. For example, the process is done as follows. The basic entry is MFV, which stands for Matte Flux Variations (as I was testing glaze results using various fluxes). This is followed by a number that represents the particular flux used in this series (helpful to add if you’re doing variations on one glaze base). The fourth flux tested, for example, would appear as MFV4. This gives you all you need to record the basic glaze. To this you add colorants, which I designate with a lowercase letter (a, b, c, etc.) to save time writing out the full name of a chemical symbol over and over again, and a number (1–6), which tells what percentage of color, (0.625%, 1%, 2%, 3%, 5%, 10%), is in the glaze, with 1 being the lowest percentage (0.625%), and 6 being the highest (10%). You end up with a number, both on the test and recorded in the book, along the lines of this: MFV4a4. Put simply this means Matte Flux Variation, made with the fourth tested flux, and 5% of a colorant. If testing is being done in both oxidation and reduction, it is helpful to append an O or an R as well, as the differences in the same glazes from the two atmospheres is often very marked. Note: It’s important to keep a key that lists what your letters, abbreviations, and numbers stand for, and the order you list them in on the tile.

Numbering tiles or other test pieces should be done on a section that will remain unglazed, with either a black underglaze pencil or pen, or by painting with a mixture of equal parts of iron and manganese mixed with a little gum and water (1). The gum lessens the likelihood of smudging the numbers. Some gums, such as gum arabic, should be mixed with alcohol, but other powdered gums may be mixed with hot water and allowed to soak overnight. This mixture can be kept in a jar and thinned with water when needed.

3. Neat and efficient working habits are essential to gain the most from your efforts. From accurate measuring and weighing of materials, through to serial numbering, and to recording observations and results, care and a certain amount of patience pay great dividends. The old fishing story of “the one that got away” need not become a reality if disciplined work habits are started from the beginning.

4. Make sure you write down everything in the notebook, even variations in firing, because over a period of time you tend to forget some important details. If it’s on paper, and the paper isn’t lost, recall comes more easily.

5. Safeguard your health with basic protection from materials that can be toxic, carcinogenic, or silicotic. Use a properly fitted respirator while mixing glazes to prevent breathing airborne dust particles. For some materials, such as wood ash, lead, and barium, rubber gloves are also helpful to prevent problems. Washing hands after using materials is also a good practice, and you should never eat or smoke in areas that may have dust contamination, or chew fingernails when glazing or mixing glazes.

3

Making Glaze Tests

Glaze and material testing can be done in a variety of ways, using tiles (1), small bowls or crucibles, extruded test forms, sections of thrown forms (2), or even clay squeezed between your fingers (3). The most important features to include are some alteration of surface, either throwing ridges or stamped, impressed patterns, and enough flat space on the unglazed portion to write or paint the serial numbers. The alteration of the surface gives some idea of how the glaze will behave on a textured background, or on thin edges, as the glaze generally runs slightly. Because of the tendency of glazes to flow, many people prefer to do testing on sections of thrown forms or some other vertical test surface. When testing new glazes or doing material fusion tests, it’s wise to make sure that the kiln shelves are well protected with a kiln wash (equal parts kaolin and silica, with added water to make a creamy mixture) or powdered silica or alumina hydrate to diminish the likelihood of ruined shelves. If tests are being done on small bowls or similar objects, a saucer or slice of insulating brick can be placed underneath to eliminate damage from running glazes.

It’s generally preferable to do glaze tests on clays that are as white as possible so the true colors of the glazes will show. I usually put a stripe of medium iron slip down one side of the tile to indicate the behavior of the glaze over a dark clay (see 1). On dark clays, I usually apply a stripe of white slip for the opposite reason (see 2, 3). It’s also useful to make an impression in the clay to indicate the quality of the glaze when pooled (see 1). The mixtures are tested on bisque-fired clay, except where the tests are for the development of glazes for work that will be fired only once.

4

Mixing Test Batches of a Glaze

The quantity of powdered materials required are measured out using a variety of methods. Pinches and handfuls, spoonfuls and kitchen measuring cups, and very sophisticated electronic scales used in chemistry laboratories are among the possibilities. Perhaps the most convenient method is somewhere in the middle of this range in the form of a triple-beam balance scale using grams as the unit of measurement. This makes it much easier to calculate percentages for adding colorants, opacifiers, and other textural additives. However you do the weighing out, do it as accurately as possible for consistent results. A small error in compounding a test batch of glaze mixture can easily become a giant one if the glaze later gets made up or mixed in a large volume. A few grams out in the test could mean a kilogram out in a large batch of glaze.

In most cases, all glaze guidelines are intended to be made up as “parts by weight” mixtures. The materials should be weighed out first. Then they can be mixed with water until the mixture is of a creamy, brushable consistency. The usual ratio of dry mixture to water is four to three for most glazes. When glazes are being made up in larger volumes, a convenient measure of dry mix to water is with kilograms and liters, where one kilogram (2.2 pounds) equals one liter (1 quart). Therefore, four kg of dry glaze mixture can be added to three liters of water for approximately the right consistency. This approximation can then be adjusted by the addition or removal of a small amount of water. Once an optimum thickness for a given glaze is established, its specific gravity can be recorded with a hydrometer.

Applying Glaze to Test Tiles

The mixtures are painted on the tiles with a variation of thickness from one end to the other, to give an indication of the behavior of the glaze with differing thicknesses. These variations can produce remarkably different results from the same glaze, and a glaze test should yield a good deal of information.

Glaze tests that are initially promising should be retested on pots, as they often seem to change character. These changes can be due to various factors: thickness, firing time, temperature and atmosphere variables, and even the more complete interaction of materials when used in bulk glaze. Before covering all your favorite pieces with inadequately tested glazes, it is advisable to spend a little more time with the groundwork. Glazes, like people, need to be lived with before they reveal their full potential. Good first impressions don’t always produce the best friends!

When you’re doing the work of glaze development (and are probably heartily sick of weighing out little bowls of powders), remember that a few days or weeks of careful testing can be enough to set you up with a lifetime of glazes, developed for your own personal requirements. The important part of the process isn’t just arriving at a good recipe or formula, but the search that led you there.

Excerpted from Robin Hopper’s book The Ceramic Spectrum, which is available at www.ceramicartsnetwork.orghttps://mycan.ceramicartsnetwork.org/s/shop.

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It's generally preferable to do glaze tests on clays that are as white as possible so the true colors of the glazes will show. I usually put a stripe of medium iron slip down one side of the tile to indicate the behavior of the glaze over a dark clay (see 1).

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It's important to wear a NIOSH certified mask whenever using dry glaze materials.
I guess mixing up glazes isn't that big of a deal, but I'm sharing my technique just in case there are some absolute beginners out there.

I find it easier to use a digital scale, see my article here.

Glazes "don't travel well", in other words materials, application, and firings vary from studio to studio. Even for well-known glazes, it's important to first make a small tests. For these tests, I use 50g or 100g of material and apply the test glaze to a number of different clay bodies.

I use the Glazy Batch Calculator on my phone which will show you the subtotals for arbitrary amounts of total glaze materials.

Once I'm happy with a test, I mix up a larger batch of 1-2Kg. 1Kg is enough material to glaze small cups, 2Kg is a good amount for small bowls. These larger tests should reveal any problems with glaze suspension (is bentonite required?), application (cracking, peeling, etc.), and fired glaze defects. Once you have some nice results with 1Kg, you can finally move on to a big bucket of 5-10Kg.

Mixing up a test

Flat test tiles require the least amount of glaze for application. Here's my article about how I make test tiles.

Sieve Mesh Size

For "natural" glazes containing large-grained materials or ashes, or in cases where homogeneity is not a concern, it's fine to use a larger screen of 60-80 mesh. But in all other cases I use 120 mesh or smaller. Small mesh size is very important for glazes that contain small amounts of very important materials such as coloring oxides (e.g. cobalt and iron). But it's also important to ensure that materials are adequately broken up and mixed (such as clays).

Below you can see two tests of the same batch of glaze fired in the same kiln. The glaze on the left was applied after passing the materials three times through an 80 mesh screen. The glaze on the right is the result of passing that same glaze once more through a 120 mesh screen.

Poorly dispersed colorants like iron are easy to see in fired glazes. But keep in mind that other "invisible" glaze ingredients like clays, feldspar, etc. also need to be well-dispersed and mixed in order to ensure the glaze melts properly. If you use a 60-mesh screen for tests and then a 120-mesh screen for large glaze batches, there will be differences between the fired results.

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It's important to wear a NIOSH certified mask whenever using dry glaze materials. I guess mixing up glazes isn't that big of a deal, but I'm sharing my technique just in case there are some absolute beginners out there. I find it easier to use a digital scale, see my article here.

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Glazing is my favourite part of the process (by which I mean developing and testing glazes, the actual dipping and pouring is less interesting) but I know a lot of potters dread it. It's understandable, it's the final stage in a long process and can easily ruin weeks of work. There's no magic cure for that, ceramics can be harsh and unforgiving, but there are ways to make the most of your glazes.

Test, Test, Test. (Then curate)

There is no substitute for time spent testing. Depending where you are on your glazing journey, this could mean a variety of different things. If you're using premade glazes, whether bought or from a shared studio, then you still have a variety of thing you can find out. You ideally should know:

What each glaze looks like at various thickness. Some glazes are totally different at different thicknesses, some are identical. You need to know if a glaze result requires a certain application.

What a glazes will look like over various clays/slips/underglazes (if you use them). Some glazes will totally change over different coloured clay. A thinner application of the Floating Blue recipe I use will be very sensitive to the clay it's on, and it's good to know that when applying it. I don't like the colour as much over white clay so I make sure to apply it thicker, but love a thin application over black slip/underglaze. I throw my test tiles with black slip on the reverse to see what a glaze will look like over two clays in one tile.

What the glazes do in combination. It's not always what you think! It's nothing like mixing paint, if they mix together you're combining two recipes to come up with a totally new one, and if they stay separate then you can get things like oil spot patterns where the physical movement of one glaze in the firing will create an entirely new pattern. Test a glaze over and under another glaze to see what works best.

If you have oxide washes, test the glazes over those too. This is similar to combining glazes, but generally more straightforward.

And if you're wondering whether you should be buying premade glazes or mixing your own, Kara has a great blog post about it. The simple answer is to do what's right for you. Making your own has a bunch of advantages in the long run, but if you're doing this in your spare time for fun then it might take quite a while to get to that stage.

If you make your own glazes but you're not comfortable with the chemistry, then you can try removing the colourant and swapping them for others. Again, this isn't like mixing paints, you might find it does something unexpected.

If you make your own glazes and understand the chemistry, then you probably don't need any of my suggestions!

And after all the testing, put all but the best tiles aside for reference later, and only continue with a tiny percentage of them. Curation is just as important as testing.

Most importantly, and I say this knowing full well that everyone will do it anyway, don't use untested combinations on pieces you like! I know it's tempting, you have a unique piece and you think you can make it even better by using a new combination of glazes that work perfectly in your head. I've done it so many times, and I've always regretted it. I know you'll still ignore it for the first few times, but hopefully it'll sink in faster for you than it did for me.

Thickness

Depending on the glaze, this can be the most important factor to getting the results you want. Clear glazes generally benefit from being thin to limit cloudiness and bubbles. Opaque glazes of a single colour can be thick or thin depending on how much you want the clay to show through. Where it becomes crucial is with layered flowing glazes. If you apply these too thinly you probably won't get the colour or movement you're looking for.

One thing you will almost certainly encounter if you try to apply multiple layers of glaze thickly is that there can be a tendency towards peeling off as the glaze dries. If you have this issue with a thin layer of a single glaze, then there are things you can do to resolve it. However, even if your glazes are perfectly happy going on in a single thick application, when combined in a thick layered application you can often have issues. There are two easy fixes.

The first is riskier but faster, and that's to apply the second glaze thinner than needed initially, then brush more onto the piece when it's dried. The brushed-on glaze will fill the small cracks that can start to form and stop them from crawling in the firing. This works well if the glazes are pretty much fine anyway, and you just want to add a little more to make sure the application is thick enough.

The second is a safer, more costly fix, and that's to bisque fire the first glaze before applying the second. It requires another firing, but this way the glaze is permanently fused in place and cannot crawl. That teapot was then layered in Chun Seafoam, a glaze that I stopped using because of how badly it wants to crawl. With the base layer fixed in place, the flaws in the top glaze can enhance the pattern created in the fired result. This technique is also useful if you want to build up a glaze to a thickness that would be a problem otherwise. Unfortunately it doesn't always work, and one of the glazes I've never got it to work with is the Snowflake/Kuan Crackles. It's a shame as they benefit greatly from a very thick application.

Some glazes will want to be fused at a temperature lower than your bisque, and you can find interesting results by fusing at the higher temperature.

Understanding your Glazes

As per the first section, understanding your glazes comes in several layers. At the basic end you just want to understand how your glazes (bought or made) behave in various different conditions. That will get you a long way, but comes with limitations. The next stage is to understand the chemistry that the glaze recipe represents, as that's all a ceramic recipe really is at the end of the day. The chemistry determines the behaviour, and the recipe is one of many ways to achieve that chemistry. By understanding what each ingredient brings to the mix, you can start to understand why recipes produce the results they do, and how to adjust them to change the characteristics.

I know I might sound like a stuck record and/or like I'm being paid to promote them (I wish!), but I honestly can't recommend the CMW classes highly enough for really getting to grips with the chemistry of the glaze ingredients. Prior to taking the course I just used recipes I found in books and online, if I had an issue with one I'd just abandon it and look for another recipe. I had a decent idea what the colourants did, and could adjust those as needed, but the base glaze was a mystery to me. The CMW are a systematic approach, where each new bit of information builds on the previous ones and puts it all in context.

It's like following origami instructions one at a time rather than being given a dozen pictures of finished cranes and being left to figure out the sequence yourself.

If you're interested in adjusting or creating glaze recipes, but don't know what all the numbers on Glazy mean, I really would recommend taking a course.

Other Tips

Smaller things that don't deserve a whole section, I'll edit more in as I think of them.

Clean your Bisqueware - Try to avoid handling the area that will be glazed, especially with dirty/oily hands. Clean off any dust before glazing. I wipe everything with a damp sponge before glazing.

Check for sharp points - Slightly contradictory to the previous point (just make sure your hands are clean first!), run your hands over the rim and handle before glazing. Any sharp points should be sanded off before glazing. Don't ignore them, they'll ruin the piece and can't be fixed after glazing. It's even better to get in the habit of also checking this before loading a bisque kiln, as it's so much easier to remove sharp points on greenware than bisqueware.

Drying - Let the pots dry overnight before firing if you can. Water in the kiln is never a good thing, especially if it's still in the piece when the temperature starts getting hot. I also have an hour hold at 100c at the start of every firing to fully dry out everything, just in case

Wax Resist - I dilute mine quite a lot, I find it goes on much easier and does a better job of letting the glaze run back off.

Drip Catchers - Great if you use glazes that can run or drip. Read more here.

Dent Pullers - Small car dent pullers can make a great tool for dipping. Make sure the bottom of your pots is smooth and wax resisted first though.

Suggestions from Instagram

I asked for glazing tips on my Instagram stories and on Reddit, here's a few of the top suggestions.

Document everything you do.

Make doubly sure there's no glaze on the bottom of the piece.

Measure the Specific Gravity.

Use a piece of wet carpet to clean glaze off the bottom of dipped pieces.

Have a plan before you start!

It's best to clean glaze splashes/mistakes off when they're dry by scraping, rather than trying to do it while they're still wet.

Always try to get at least one experiment into every kiln load.

Wax resist on the wheel rather than freehand.

Make sure your glaze is mixed thoroughly before applying. You can use an immersion blender or an electric drill with a mixer attachment, or just shake it if the container is small enough. And remix if you've been using a glaze for a little while, it will separate back out over time.

Try to keep an open mind when evaluating results. Give yourself the evening and sleep on it. Tiles look different the next day

When layered glazes crack: deflocculate! A drop or two of sodium silicate will make the glaze hold onto less water and it will stop it from cracking.

If your glaze hard pans, it's not worth it to use it. Spending 20 minutes mixing it up to dip a piece that doesn't turn out well because you still didn't get everything stirred up is a waste of time and kiln space.

If there's anything you'd add to the list, please leave it in the comments below!

Please let me know how you get on, message me or use the hashtag oldforgecreations (I often miss @mentions on Instagram and there's no way to find them afterwards, but I'll see the tag). Good luck!

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Glazing is my favourite part of the process (by which I mean developing and testing glazes, the actual dipping and pouring is less interesting) but I know a lot of potters dread it. It's understandable, it's the final stage in a long process and can easily ruin weeks of work.

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I know how much dry glass forming material is in the big base batch (3,000g). I know the total weight of all the material in the base glaze (6,825g). I know the weight of the smaller portioned out glaze batches (100g). Now I just have to solve for X (which is the amount of dry glass forming material in the small portions).

I solve for X using cross-multiplication.

3,000g X 100g / 6,825g = 43.96g
X= 43.96g

X=43.96g. This is the weight I will use to calculate the correct percentage of colorant to add to each 100g wet batch. I am testing 5% additions of stains in this glaze.

So 43.96g x 5% = 2.198g stain added to each 100g wet batch. I use a scale that measures two decimal points for greater accuracy. Measuring out each stain at 2.18g - 2.20g. Weigh the colorants in a separate container then add them to the wet glaze.

To mix all these separate little containers of glaze/colorants thoroughly and quickly, I use a milk frother wand. This allows me to mix the colorants into each little batch in a matter of a few seconds, with no additional sieving necessary. The battery powered milk frother is fine if your only going to test a few batches every so often. But if you are really into colorant / glaze testing I recommend cutting off the frother part and using it in a Dremel. I use the lowest setting on the Dremel, around 5,000 rpm, any more than this and the frother head will start to wobble and your glaze will go flying out of the container. NOTE! These milk frother wands are not meant for these kinds of rpms, it works but be safe and aware of the tool. Also if you're going to use a Dremel, make sure you get a milk frother that has the "squirrel cage" type frothing head(like in pic 4). It is centered and doesn't vibrate at the higher rpms like the other kinds do.

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Best Practice Glaze Testing - Rat City Studios

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I know how much dry glass forming material is in the big base batch (3,000g). I know the total weight of all the material in the base glaze (6,825g). I know the weight of the smaller portioned out glaze batches (100g).

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Mixing Recipes

Glazes "don't travel well", in other words materials, application, and firings vary from studio to studio. Even for well-known glazes, it's important to first make a few small tests. For these tests, use 50g or 100g of material and apply the test glaze to a number of different clay bodies. If a test comes out well, mix a larger batch of 1-2Kg. 1Kg is enough material to glaze small cups, 2Kg is a good amount for small bowls. These larger tests should reveal any problems with glaze suspension, application (cracking, peeling, etc.), and fired glaze defects. Once you have some nice results with 1Kg, you can finally move on to a big bucket of 5-10Kg.

Batch Calculator

The batch calculator simply multiplies each ingredient amount. It is unit-independent. In the example shown, it does not matter if we are making 2000 grams, kilograms, pounds or even tonnes of glaze.

Note that additive materials such as coloring oxides are calculated in addition to the batch amount.

In the example below, the base recipe is calculated to 1000 units (grams, pounds, whatever), while the additional materials (Tin Oxide and Yellow Iron Oxide) are added on top of 1000.

Sieves

For "natural" glazes containing large-grained materials or ashes, or in cases where homogeneity is not a concern, it's fine to use a larger screen of 60-80 mesh. But in all other cases it's good to use 120 mesh or smaller. Small mesh size is very important for glazes that contain small amounts of very important materials such as coloring oxides (e.g. cobalt and iron). But it's also important to ensure that materials are adequately broken up and mixed (such as clays).

Below you can see two tests of the same batch of glaze fired in the same kiln. The first test was applied after passing the materials three times through an 80 mesh screen. The second test is the result of passing that same glaze once more through a 120 mesh screen.

Scales

Weight measuring scales come in a wide range of types and prices. Purchasing a scale is a trade-off between cost, resolution and capacity. In general, scales that can weigh larger amounts of materials have lower resolution (e.g. 1 gram), while scales that have higher resolution (e.g. 0.01 grams) can only weigh small amounts.

For weighing small amounts of glaze materials (for example, 50 and 100 gram test batches), it is very important to use a scale that has a readability to at least 0.1 grams. (Some glaze materials such as cobalt are very strong, and a difference of even 0.1 grams in a 100 gram batch will have a noticeable impact.) Ideally, your test scale will have a capacity of over 100 grams and readability of 0.01 grams.

Note: Just because a scale has a high resolution (e.g. 0.01 grams) does not mean it has high accuracy. Price is usually a good indication of accuracy, so it's best to get the most expensive scale that you can reasonably afford.

The Ohaus Scout Pro SP4001 and SP202 digital scales during calibration. It is important to periodically calibrate your scales using accurate calibration weights.

Using a Beam Scale

For those on a budget, perhaps the most affordable solution for precise weighing of glaze materials is a triple beam scale .

1. Select a container to hold glaze materials and weigh it on the scale. In the example below, the container weighs 63 grams:

2. On the Glazy recipe page, enter the Tare Weight:

3. Enter the Batch Size. The batch size is unit independent.
In the below example, we could be measuring 400 grams, 400 pounds,
or even 400 tons of recipe material. But in this case, we are using grams.
Notice that the final subtotal equals 463, which is the Tare Weight
(weight of the container) plus the Batch Size.

4. After measuring out the first ingredient, EPK, our scale should
show 251 (63 grams container weight plus 188 grams of EPK):

5. After measuring out all of the ingredients for this batch,
the scale should read 463 (63 gram container plus 400 gram batch):

Mixing Test Glazes

It's important to wear a well-fitting, NIOSH certified mask whenever mixing ceramic materials. All materials should be handled in well-ventilated area to avoid the risk of inhalation. For more information about the hazards of mixing ceramic materials, see the article Studio Dust by Mark Goldberg.

For test glazes, try to find re-useable containers that fit your seives like these plastic restaurant soup bowls with lids. Glaze name & recipe can be written on the container with permanent marker.

Carefully measure out each ingredient into the bowl, placing into separate piles so that any extra material can be easily removed. The measurement displayed on the scale should match the "Subtotal" column in the Glazy Batch Calculator.

Dry mix the ingredients with a spoon until well dispersed.

For 100 grams of material, add about 50-60ml of water (less if your glaze has little or no clay).

Wait a few minutes until the water has thoroughly soaked the materials, then stir. Glaze should be fairly thick, do not add too much water as you will be adding more as you go along.

Use a fairly stiff rib to scrape the glaze through the sieve.

The first pass takes the most work as the clays are broken apart.

Try not to lose any material, especially if preparing for volumetric blending. Use a water sprayer to clean the container, spoon, and sieve after each pass. But don't add too much water.

Pass the glaze through the sieve two or three times. After the final pass, the glaze should be creamy without any large grains or lumps.

Now you can slowly mix in water and dip your test tiles. Flat test tiles require the least amount of glaze.

Test tiles can be dipped multiple times in order to see the result of glaze thickness. It is best to double-dip the side of a test tile rather than the top so that the two different glaze thicknesses do not run into one another.

Record as much information as you can on each test tile. On this tile, the type of clay has been stamped, while glaze information was written with an underglaze pencil. After firing, a permanent marker was used to record the firing date and actual cone reached.

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Mixing Recipes Glazes "don't travel well", in other words materials, application, and firings vary from studio to studio. Even for well-known glazes, it's important to first make a few small tests. For these tests, use 50g or 100g of material and apply the test glaze to a number of different clay bodies.

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The study of ceramic materials is at the center of all ceramic technology. While knowing the chemistry of materials gives you much control of fired the properties of glazes, knowing the physical and fired properties of materials enables control of both fired and unfired properties of bodies (and of course of the physical and working properties of glaze slurries). In education students study theoretical materials, in industry we work directly with real-world materials, we can see them and touch them. These materials normally come in bags, they are powders and we understand their properties from this view (not from the rocks they once were in a quarry). They have plasticities, melting temperatures, particle size distributions, vitrification histories, solubility or solubles contents, impurities, consistency issues, rheological properties, bulk densities, particle surface areas, costs, etc.

Materials science needs to be put into context with all the levels of assessment: oxide, mineral, material, recipe and process. For example, consider the problem of ware cracking during drying, a body issue (not likely related to chemistry). The problem could be as simple as ware being dried unevenly, a process level problem. If the cracking is occurring because the body has been formulated with too much ball clay to make it practical to dry, that is a recipe level issue. If the cracking is occurring because one material has changed or been substituted, perhaps to a much smaller particle size alternative, that is a material level issue. If the cause of the problem is difficult to asses, then the mineralogy of the ingredient materials and their interactions may need to be studied and understood better to solve the problem.

In many cases the causes of a problem have roots on multiple levels. Amazingly, this affords the opportunity to link apparently separate problems occurring on multiple levels and solve them all at once. Consider the issue of a glaze slurry that is settling quickly, powdering after drying and failing to adhere well to ware, these are happening because of lack of clay content. This problem is probably directly related to the fact that the glaze is also running off ware during firing (likely due to lack of and in the glaze). Adding kaolin (which supplies both) will help suspend and harden the glaze and it will help stabilize it during firing, solving all the problems. In addition the glaze will also be more durable and less soluble.

In this materials area of the database we avoid discussing too much about chemistry, this is done in the oxides area. For example, on the material level we see kaolin as clay powder that contributes plasticity to a body and suspension properties to a glaze (while of course contributing Al ₂O ₃ and SiO ₂ to the chemistry of the glaze and a mullite building source to the body). On the mineral level it is kaolinite, its properties compare to other clays in relation to its particle size and shape, surface chemistry on the particles, etc. On the chemistry level it is no longer kaolin, it is Al ₂O ₃ and SiO ₂, therefore studying its effects on glazes involves studying these two oxides. However there a limitations to this 'materials as chemistry sources' view, different materials of the same chemistry do not release their oxides into a melt with the same willingness. These differences can be answered on the mineral level.

The concept of distinguishing between generic materials and name-brand materials enables maintaining general information in fewer places. For example, all generic information about kaolin can be found in the generic kaolin record. Other name-brand kaolins are linked to the generic kaolin as their parent and only information specific or unique to them is recorded there. Generic kaolin is, in turn, linked to the mineral kaolinite.

If you have studied or compared data sheets over a period of time then you know how many errors they can have, how unclear they can be, how non-applicable or non-practical their data is for ceramic applications and how drastically numbers can change as companies update them. This underscores the importance of being able to test these materials for yourself to know the behaviour for specific properties that relate to your application.

Links

Lab testing a clay for its physical properties

It only takes a few minutes to make these. But you would be amazed at how much information they can give you about a clay! These are SHAB test bars, an LDW test for water content and a DFAC test disk about to be put into a drier. The SHAB bars shrink during drying and firing, the length is measured at each stage. The LDW sample is weighed wet, dry and fired. The tin can prevents the inner portion of the DFAC disk from drying and this sets up stresses that cause it to crack. The nature of the cracking pattern and its magnitude are recorded as a Drying Factor. The numbers from all of these measurements are recorded in my account at Insight-live. It can present a complete physical properties report that calculates things like drying shrinkage, firing shrinkage, water content and LOI (from the measured values).

Refined 200 mesh materials are not guaranteed to be such

Each of these eight pallets of kaolin are being sampled to screen them for oversize particles. The 50 gram samples needed can be taken without having to open the bags, they are filled through a valve at the top and it can be opened easily. Kaolins and ball clays especially are suspect and body manufacturers must be vigilant about this (each can tell you disaster stories about making product with faulty raw materials containing grit, carbon and iron particles). The samples will be washed through 70, 100 and 150 mesh screens to spot any particles that could introduce grit or fired speckle into the bodies.

Do not rely on material data sheets, do the testing

The cone 6 porcelain on the left uses Grolleg kaolin, the right uses Tile #6 kaolin. The Grolleg body needs 5-10% less feldspar to vitrify it to zero porosity. It thus contains more kaolin, yet it fires significantly whiter. Theoretically this seems simple. Tile #6 contains alot more iron than Grolleg. Wrong! According to the data sheets, Grolleg has the more iron of the two. Why does it always fire whiter? I actually do not know. But the point is, do not rely totally on numbers on data sheets, do the testing yourself.

When both mineralogy and chemistry are shown on a data sheet

Some material data sheets show both the oxide and mineralogical analyses. Dolomite, for example, is composed of calcium carbonate and magnesium carbonate minerals, these can be separated mechanically. Although this material participates in the glaze melt to source the MgO and CaO (which are oxides), it's mineralogy (the calcium and magnesium carbonates) specifically accounts for the unique way it decomposes and melts.

Lignite contamination in manufactured porcelain bodies

These particles contaminating particles are exposed on the rim of a bisque fired mug. The liqnite ones have burned away but the iron particle is still there (and will produce a speck in the glaze). Remnants of the lignite remain inside the matrix and can pinhole glazes. Since ball clays are air floated (a stream of air takes away the lighter particles and the heavier ones recycle for regrinding) it seems that contamination like this would be impossible. But the equipment requires vigilance for correct operation, especially when there is pressure to maximize production. Ores in Tennessee are higher in coal than those in Kentucky. North American clay body manufacturers who confront ball clay suppliers with this contamination find that ceramic applications have become a very small part of the total ball clay market, complaints are not taken with the same seriousness as in the past.

By Tony Hansen

https://digitalfire.com, All Rights Reserved
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The study of ceramic materials is at the center of all ceramic technology. While knowing the chemistry of materials gives you much control of fired the properties of glazes, knowing the physical and fired properties of materials enables control of both fired and unfired properties of bodies (and of course of the physical and working properties of glaze slurries).

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The Right Chemistry for a Cone 6 MgO Matte
The Trials of Being the Only Technical Person in the Club
The Whining Stops Here: A Realistic Look at Clay Bodies
Those Unlabelled Bags and Buckets
Tiles and Mosaics for Potters
Toxicity of Firebricks Used in Ovens
Trafficking in Glaze Recipes
Understanding Ceramic Materials
Understanding Ceramic Oxides
Understanding Glaze Slurry Properties
Understanding the Deflocculation Process in Slip Casting
Understanding the Terra Cotta Slip Casting Recipes In North America
Understanding Thermal Expansion in Ceramic Glazes
Unwanted Crystallization in a Cone 6 Glaze
Volcanic Ash
What Determines a Glaze's Firing Temperature?
What is a Mole, Checking Out the Mole
What is the Glaze Dragon?
Where do I start in understanding glazes?
Why Textbook Glazes Are So Difficult

Description

There is more to glazes than their visual character, they have other physical properties like hardness, thermal expansion, leachability, chemistry and they exhibit many defects. Here are some simple tests.

Article

What if you could greatly increase the quality of your fired ware by only small changes? Would you do it? Testing it thoroughly is a key ingredient. But mention the idea of testing a glaze and 99% of us think in terms of dipping a test tile and firing it to see how it looks. Many have learned that there is often little correlation between how a glaze looks on a little test tile compared with how it looks when used on ware, thus they tend to put little effort into testing. However if you already have a glaze in production, or have made an adjustment to an existing one, you are likely willing to expend much more effort to evaluate it fully.

Raw and fired glazes exhibit many properties that both production and end users are knowingly or unknowingly concerned with. These include slurry properties, dry hardness, behavior of the melt, freezing characteristics, hardness and scratch resistance of the fired glass, compatibility of host glaze and added colorants, leach resistance, glaze fit with the body, clarity of the fired glass, etc. Certain factors such susceptibility to material change and varying firing conditions are more difficult to measure.

Most people and companies do not have fancy glaze testing equipment to evaluate these properties. It is to these that this article is directed, there is much you can do to greatly increase your confidence in the true 'quality' of your product. Testing your glaze thoroughly is doubly important if you are using one or two base glazes because, in a sense, you have all your 'quality eggs in one basket'. We 'hoot' a lot about the advantages of focusing your efforts on one base glossy and matte recipe and altering these to make whatever you want. Thus the following tests all assume and depend on the fact that you are testing the transparent base without any colorants, opacifiers, or other additives. Remember that improving the base improves every recipe that is based on it.

Here are some tests you should consider:

Slurry Properties
Mix a small pail of the glaze and bring it to the proper consistency (I am assuming you are glazing bisque ware). Most glazes work best when there is enough water to make them fluid and not so much that they do not gel. Typically you should be able to stir a glaze with a stick, pull the stick out, and the slurry should remain in motion only for 2-4 seconds. Measure its specific gravity and record this amount. If in future the glaze gels, settles, or runs excessively check its specific gravity. If it is correct then you need to investigate changes in your water supply or dry materials that could flocculate or deflocculate the slurry.
Let the container of glaze sit overnight and check it the next day for any tendency to settle or gel excessively. If it settles incorporate some bentonite in the recipe. If it gels to the point that remixing does not thin it out then replace materials known to be soluble (i.e. Gerstley Borate, Nepheline Syenite) or use distilled water.

Application Properties
Dip your dry finger into the slurry and pull it out. Only one or two drips should fall and a good layer of glaze should hold itself in place. For glazes intended for application to bisque ware, dip a thick test tile (2 cm thick) all the way in for two seconds, pull it out and turn it over and watch for any tendency to run and drip. Note how quick it dries. When dry dip it again half way and hold it in for several seconds. Set it out to dry and note any tendency of the glaze cover to crack during drying (this is an indication of too much clay or too plastic clay in the recipe). When the specimen is completely dry note its tendency to 'powder off' in your hands. Will it accept overglaze painted decoration without turning to mud or will wax resist paint on and hang on well (if not the clay content is either too low or not plastic enough).
Dip a thin test tile also (5mm thick or less) and apply thick and thin layers as above (the tile should be thin enough so that the clay becomes waterlogged and the glaze thus dries slowly). Note any tendency of the glaze to bubble as it dries, this indicates that the specific gravity of the glaze may be too low.

Crystallization, Clarity, Crawling
Fire the thick and thin test specimens made above. The thick one will cool slower, note any tendency for it to devitrify (develop crystals) compared to the thin one. Note any tendency toward crawling on the thickly glazed sections of the specimens, especially near edges. Note any tendency of the glaze to cloud with bubbles in the thicker areas.

Stain Compatibility
Using a small brush paint stain ID numbers and color swatches on a flat tile of the target clay body. Glaze the whole tile over with a transparent version of the base glaze you are testing and fire. Note colors that are off and research the required chemistry to explain why.

Leaching
Add a colorant like cobalt to a transparent version of the glaze being test, make and fire a bowl, fill it with vinegar and leave it in a warm place for twenty four hours. Note any fading of color, reformulate and test again till no leaching occurs.

Hardness
Take a sharp concrete nail and attempt to scratch the glaze. Compare its performance against a benchmark glaze that has proven to be durable. Or use a hardened steel file to attempt to remove glaze on the lip or corner of a piece.

Cutlery Marking
Using the edge of a stainless spoon or fork attempt to mark the surface of the glaze. If it marks attempt to rub or clean the mark off. If you cannot consider reformulating the glaze to develop a smoother surface or fewer crystals, flux it to melt more, or fire it higher.

Crazing, Shivering
Cycle a thin glazed shard of your body-glaze combination between three-minute immersions in boiling water and ice water. Do it three times. Use a black marker to color an area of the surface. Clean the ink off using methyl hydrate. Note any craze lines highlighted by the ink. Note any areas near edges that may be flaking off (shivering). Reformulate the glaze to reduce its thermal expansion (increase it for shivering), fire, and test again.

Glaze Over Solubles
Prepare a 12cm diameter disk 5mm thick from your clay and dry it under a fan with the center 6 cm covered. Any soluble salts in your clay body will be amplified on the outer 3cm ring. Break the disk in half, glaze half, and support and fire it resting on the flat. Note any reaction between the soluble salts in your clay and the glaze (i.e. blistering, orange peeling).

Flow
Check the flow of the melt using a flow tester.

Fired Volatility
Many glazes work well at one temperature but if fired slightly higher or lower they can have a much different surface. This type of behavior is normally only tolerated in very special purpose glazes. Thus you should prepare sample tiles for firing one cone higher and lower than you working temperature. This will help you spot possible trouble in future if kiln firings are not totally consistent.

Microscope
Using a $20 30X Lightscope (available at hardware stores) look carefully at the glaze surface for any signs of poor melting (especially in matte glazes) or surface pits that could harbor bacteria. Identify any tiny specks as either impurities or the first stages of crystals. Break a shard and check for a good interface between glaze and clay. Examine any scratches you were able to make with the concrete nail.

Make Functional Ware
Mix a couple of gallons of the base glaze and make a variety of functional ceramic shapes, glaze, and fire them. Note any problems like pinholing, crawling, bubbling, devitrification, and blistering.

Related Information

A batch of fired clay test bars in the Plainsman Clays lab

A batch of fired test bars that have just been boiled and weighed, from these we get dry shrinkage, fired shrinkage and porosity. Each pile is a different mix, fired to various temperatures. Test runs are on the left, production runs on the right. Each bar is stamped with a code number and specimen number (the different specimens are the different temperatures). The measurements have all been entered into our group account at insight-live.com. Now I have to lay out and photograph each pile and upload the picture into the code-numbered record. Upon doing so I compare color and tests results to make decisions on what to do next (documenting these in insight-live).

Measuring slip viscosity using a paint-measuring device

A Ford Cup being using to measure the viscosity of a casting clip. These are available at paint supply stores. This is a #4, it holds 100ml and drains water in 10 seconds (it has a 4.25mm opening). This casting slip has a specific gravity of 1.79 and we target a 40-second drain. That being said, if you are not working in a factory, if will be sufficiently to eye-ball the viscosity as you gain experience. If you are in a high-production situation, the seconds-value that this test produces gives you something to write down in testing records, producing an audit-trail for quality control and problem solving later. One thing to note: A slurry can gel while it is draining, if this happens the value produced is not valid. First adjust the rheology so it maintains viscosity throughout the drain time.

Feldspars, the primary high temperature flux, melt less than you think.

A cone 8 comparative flow tests of Custer, G-200 and i-minerals high soda and high potassium feldspars. Notice how little the pure materials are moving (bottom), even though they are fired to cone 11. In addition, the sodium feldspars move better than the potassium ones. But feldspars do their real fluxing work when they can interact with other materials. Notice how well they flow with only 10% frit added (top), even though they are being fired three cones lower.

Links

Articles

Limit Formulas and Target Formulas
Glaze chemistries for each type of glaze have a typical look to them that enables us to spot ones that are non-typical. Limit and target formulas are useful to us if we keep in perspective their proper use.

Articles

G1214W Cone 6 Transparent Base Glaze
The process we used to improve the 20x5 base cone 6 glaze recipe

Articles

A Low Cost Tester of Glaze Melt Fluidity
This device to measure glaze melt fluidity helps you better understand your glazes and materials and solve all sorts of problems.

Projects

Frits

Projects

Tests

Troubles

Glaze Marks or Scratches
Questions to ask and strategies to try to deal with glaze cutlery marking, that is, glazes that are too easily scatched by metal.

Glossary

Characterization
In ceramics, this normally refers to the process of doing physical or chemical testing on a raw material to accurately describe it in terms of similar ones.

By Tony Hansen

https://digitalfire.com, All Rights Reserved
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Low Budget Testing of the Raw and Fired Properties of a Glaze

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There is more to glazes than their visual character, they have other physical properties like hardness, thermal expansion, leachability, chemistry and they exhibit many defects. Here are some simple tests.

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A Simplified Ceramic Chemistry Lesson A Little Ceramic Chemistry to Help You Better Understand Glaze Composition Linda Bloomfield

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Published Oct 12, 2021

Dive into some ceramic chemistry today! The recipes used on this turquoise and yellow egg tray by Andrea Denniston are included below.

If you’re like me, the mention of the word chemistry can send you into a panic–admittedly not my favorite subject. But I love ceramics, so I realized a while back that I had to face my fears and try to get a grasp on ceramic chemistry.

Yes, a general knowledge of ceramic chemistry and glaze materials can be very helpful when mixing glazes and interpreting firing results. In this post, an excerpt from Science for Potters, Linda Bloomfield breaks down what potters need to know on the Periodic Table of the Elements. We also included a couple of great cone 6 glaze recipes so you could put some of this new knowledge into practice. Get your thinking caps on! We’re going back to school! - Jennifer Poellot Harnetty, editor.

P.S. For more detailed information about elements from the periodic table that are relevant for ceramic artists, atom structure, and electrons and orbitals, check out Science for Potters by Linda Bloomfield in the CAN shop.

Ceramic Chemistry – The Elements
The elements were forged in nuclear furnaces inside stars. Ordinary stars like the sun burn hydrogen, two hydrogen atoms colliding together to make a helium atom and releasing energy in the form of heat and light. In dying stars, the hydrogen runs out and the helium atoms fuse together to make the heavier elements. Elements heavier than iron, such as lead and uranium, are only formed when a massive star explodes to become a supernova. The dust left from such an explosion eventually re-forms to make new stars and planets like our Earth. We are all literally made of stardust.
In the ancient world, the elements, or basic constituents of matter, were believed to be earth, air, fire, and water. We now know that there are in fact more than 90 naturally occurring elements, including metals, semi-metals, and non-metals. At ambient temperature, some elements exist as gases, a few as liquids, and many as solids, but their state of matter can change with temperature. As potters we are most interested in the elements in the Earth’s crust that form rocks, as these are also the elements present in clay and glazes. The most abundant are oxygen, silicon, and aluminum, followed by iron, calcium, sodium, potassium, and magnesium (1).

Ceramic Chemistry – The Potter’s Periodic Table
The periodic table explains the chemical and physical properties of the different materials used by potters (4). It is the basis for understanding the whole of chemistry. However, we are primarily interested in the elements useful to potters, which include silicon, aluminum, the alkali metals and alkaline earth metals, as well as the transition metals.
During the nineteenth century, scientists began to notice that groups of elements had similar properties. Not all the elements had yet been discovered, but when they were lined up in order of increasing atomic number in seven rows, similarities between groups became clear. We know now that is because the elements in a group all have the same number of electrons in their outer shell, so they all react in similar ways.

In the periodic table, the elements are listed in order of ascending atomic number. There are seven rows of elements and eighteen columns. The elements in each column, called a group, have similar properties. Important groups for the potter are group 1, the alkali metals (sodium, potassium etc.), and group 2, the alkaline earth metals (calcium, magnesium etc.). These are used as fluxes in glazes. All the elements on the left-hand side and middle of the periodic table are metals. The ones at the bottom are known as heavy metals as they have more protons and neutrons and therefore greater atomic weights. Many of the metals discovered since the early nineteenth century have names ending in ‘-ium’, for example, sodium, calcium, barium. Their oxides form alkaline solutions when dissolved in water. The oxides, rather than the metals, are of most interest to the potter as they are the constituents of clay and glazes.

The central block of the periodic table contains the transition metals. These can have several oxidation states and are important in producing colored glazes, particularly the metals along the top row: chromium, manganese, iron, cobalt, nickel, and copper. The two rows inserted at the bottom are known as the lanthanides and the actinides, and some can also produce colors in glass and glazes. Uranium is the heaviest naturally occurring element and can produce yellow in glazes, although it is no longer used owing to its radioactivity. The elements beyond uranium can only be synthesized in nuclear reactors and decay radioactively into other elements. Lead is the heaviest stable, non-radioactive element.

Andrea Denniston's Glaze Recipes.

On the right-hand side of the periodic table is a diagonal line, which divides metals from non-metals. The elements on this line include boron, silicon, and arsenic. They are known as metalloids and are semiconductors, which means they will only conduct electricity under certain conditions. Silicon is the basis of modern electronics and computers. Some of the elements most useful to potters also lie on or near this dividing line and include silicon and boron, which are both glass formers although the latter is mainly used as a flux in low-temperature glazes and in heat-resistant borosilicate glass. Aluminum is next to silicon, found in clay and used as a stabilizer in glazes, preventing them from becoming too runny when fired. On the right-hand side of silicon is phosphorus, used as a flux in glazes and in bone china. Antimony and selenium are used in small amounts as yellow and red colorants in glazes.

Andrea Denniston's egg tray with above glazes.

The top right-hand corner of the periodic table contains oxygen, the halogens fluorine and chlorine, and the noble gases helium and neon. Oxygen is present in all clay and glazes, usually combined with silicon and aluminum as oxides. Fluorine is of interest to the potter, as it is often given off in the kiln from decomposing fluorspar, a mineral found in Cornwall Stone.

The far left of the periodic table is highly alkaline and the right is highly acidic. The strength of the alkali decreases from left to right, while the strength of the acid increases. For example, along the third row, sodium oxide (Na2O) is highly alkaline, magnesium oxide (MgO) is alkaline, aluminum oxide (Al2O3) is amphoteric, silicon dioxide (SiO2) is acidic, and phosphorus pentoxide (P2O5) is highly acidic. In ceramic glazes and vitreous ceramic clay bodies, the alkaline and acidic oxides react together and melt. The alkaline metal oxides are fluxes, which react with the acidic glass former, silica. The elements in the central block are amphoteric (able to react as an acid or base/alkaline), although many show slightly alkaline or acidic properties. Their oxides are used in glazes as supplementary fluxes, stabilizers, opacifiers, and colorants.

**First published in 2017.

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Ceramic Chemistry - A Simplified Lesson to Help Potters

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A general knowledge of ceramic chemistry and glaze materials can be very helpful when mixing glazes and interpreting firing results. In this post, potter and scientist Linda Bloomfield gives a simplif

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Studio safety is key to living a long and healthy life as a potter. In our line of work, we can come into contact with many different job hazards that can cause us grief down the road. Being cautious and taking preventative measures is the best way to stay safe in the studio for the long term. In this article, we have 10 ways to make your studio safe and 10 ways to keep yourself safe and healthy while pursuing your passion for pottery.

How to Make your Studio Safe

1. Don't let clay sit out

When you let clay sit out to dry and then it is moved around or brushed, silicate dust can be stirred up. This most commonly happens at pottery wheels where the trimmings might be left out and can become bone dry over time. It is important to take precautions and wet the dry clay to capture the silicate dust before it becomes airborne and then clean the area up. Cleaning your pottery wheel regularly, storing clay in containers or bags, and removing clay trimmings when they are still leather hard is best for keeping the dust to a minimum in the studio.

2. Wipe down surfaces

Wiping down surfaces will trap particles before they become airborne. This is important for clay dust that occurs from trimming and clay or glaze mixing. When there is a large amount of dust, spraying down the area or wiping it down with a wet cloth or sponge can trap the particles and keep you safe from inhaling particles into your lungs. Keeping multiple sponges or rags can help make it easier and more of a regular habit to clean up surfaces when you are done working.

3. Keep powders stored

Keeping powders stored in air tight containers is best for your health, and the longevity of the powders. When powders are stored it prevents you from inhaling the particles that might get stirred up if left uncovered. Another benefit of keeping your powders stored is that it prevents moisture or other contaminants from getting mixed into the powder and ruining the integrity of it. There are many different container sizes that can accommodate powders of all quantities.

4. Have your kiln in a safe location

Having a safe kiln location can help prolong the life of your kiln and stop any potential fires from occurring as well. Concrete is the optimal flooring to have, and keeping the kiln far away from walls and other kilns will prevent the heat from melting anything near the kiln. Be sure to keep all flammable materials and liquids far away from the kiln in order to prevent fires and explosions from occurring. Remember to use metal shelves instead of wooden ones if they are close to your kiln.

5. Emergency Shut off

Having an emergency shut off for kilns and other powered tools is important when things go awry. A breaker for the kiln can shut off the power to the electric kiln in case there is a serious issue. Other tools such as pugmills, slipcasting machines, drills, and so on should be shut off immediately and then unplugged if there is something wrong with it. These steps can help ensure that the machine is not accidentally turned back on during the emergency or when it is being inspected.

6. Clean pottery tools

Clean pottery tools are important for the longevity of your tools and the safety of yourself. If you have a rusty tool and cut yourself you will need to worry about tetanus. Cleaning your pottery tools once you are done with them can help your tools to last for a very long time. It also helps to prevent silicate dust from getting stirred up when you are digging around a drawer filled with clay covered tools.

7. Keep toxic liquids contained

Toxic liquids should be contained in a cabinet when not in use in order to prevent spills and unintentional exposure to said liquids. These liquids should be clearly labeled and handled with care depending on the toxicity of the chemical. Remember to keep warning labels on the front of these containers too in order to know what to do when you are exposed to the chemicals.

8. Toxic fumes get vented

Venting toxic fumes is very important to staying healthy in the studio. It can be very hazardous to your health to breathe in chemicals that can cause you to be sick or pass out from exposure to it over time. Remember to be safe and use a vent and respirator or work outside and wear a respirator .

9. Clean regularly around the studio

Cleaning the studio can help you organize your tools and clean away clay dust that manages to get everywhere. Long-term exposure to silicate dust can cause serious damage to your lungs so cleaning up the floors, tables, around wheels and tables can go a long way to keeping your lungs healthy.

10. Venting the studio

Venting the studio can be important when there is a build up from lack of cleaning in the studio. Opening windows and doors can help to remove dust and particles in the air that might cause damage to your health over a long period of time. Fresh air introduced into the studio can also help remove any funky smells that might have occurred from moldy clay or reclaim.

How to keep yourself safe and healthy

1. Wear a respirator

Wearing a respirator is very important when doing certain tasks in the studio. These tasks include cleaning dusty areas, mixing glazes, mixing clay, handling and using toxic liquids, and measuring powders. A respirator can help prevent particles that become airborne during any of these tasks from getting into your lungs and causing long-lasting damage.

2. Wear proper footwear

If you do not wear proper footwear, which is a pair of closed toe shoes , then serious damage can occur to your feet. Dropping tools, hot bisqued or glazed pieces, or kiln furniture can cut your feet up or even break some bones. Wearing the right footwear in the studio can help keep your feet safe and injury free.

3. Take care of injuries

Taking care of injuries is important as soon as they happen. This includes burns, cuts, and more serious wounds. Its best to have a first aid kit in your studio, they cost less than $50 and can even be mounted to the wall . Our hands and feet are very important to our craft and it is important to take care of ourselves as much as we take care of our pottery. Treating wounds and staying away from chemicals with open wounds is important to avoid infections and longer recovery times. Be sure to wear gloves if you have a wound on your hand and you are handling clay or glaze. For more serious wounds it might be best to stay out of the studio until you are fully healed to ensure that you do not injure yourself further.

4. Wash hands regularly

Washing your hands after you are done wheel throwing or glazing can be very helpful to keep your hands and body healthy. Keeping the clay on your hands can cause your hands to dry out severely and eventually crack and bleed if you do not moisturize. We recommend using Porter's Original Lotion and Udderly smooth to keep your hands in tip-top condition. Keeping glaze on your hands after glazing can mean that you accidentally get glaze in your mouth or eyes, which is extremely harmful and unpleasant. Keeping your hands clean when you are not in the middle of glazing or working with clay can ensure that you do not dry out or consume anything by accident that is on your hands.

5. Use proper venting

Proper venting in the studio can help alleviate built up dust and gasses that might accumulate depending on the work that you do in your studio. Smelly chemicals such as gold luster will need to be vented out since they are potent and can cause headaches if exposed to the smell for too long. Remember to air out your studio and use proper venting when mixing glazes since a lot of dust will be up in the air from mixing. It is also a good idea to wear a respirator as well to keep your lungs safe from small particles in the air that get stirred up while mixing glazes and clay.

6. Use protective eyewear

Protective eyewear is important when grinding down excess glaze. Glaze shards can fly off from the grinding wheel and end up in your eyes if you do not have protective eyewear . Face shields are also a good alternative to keep your entire face safe while grinding down the bottom of your work.

7. Keep track of your tools

Keeping track of your tools is important to avoiding possible hand injuries or tools getting into machines. Remember to check your bucket after throwing to ensure that tools and sponges do not end up in a reclaim bucket or pugmill. It is important to delicately check your bucket so you do not end up stabbing yourself with your needle tool while reaching into the bucket to grab the reclaimed clay. We recommend using a wall mounted tool mount to store your tools.

8. Stay hydrated

Staying hydrated in the studio is very important to feeling energized and awake while working. If you find yourself feeling tired or drained, then drinking water regularly out of a water flask , might be able to help you. When you are dehydrated it can cause feelings of nausea, faintness, fatigue, dizziness and so on. Even if you do not feel thirsty you can be dehydrated so remember to drink water regularly.

9. Do not eat in the studio

Eating in the studio can be very unsanitary. You could end up with clay, dust, or glaze on your food which you will then consume. Stepping outside of your studio can be a good break and a good way to prevent anything in your studio from ending up on your food.

10. Do stretches

Stretches are important to keeping our bodies healthy over time as potters. We bend over a lot from wheel throwing, wedging, working long hours on sculptures, and so on. Taking a break every 15 minutes to get up, stretch, and walk around can prevent you from developing back problems and other spinal problems down the road. Here is a 5 minute Yoga Routine that you can do whilst sitting down in your studio (Music by Mr. j Medeiros )

Pottery Studio Safety Conclusion

In conclusion, the studio is a fun place to be, where you can create beautiful and one of a kind pieces. However, it is important to be safe while in the studio to keep yourself healthy down the road and prevent health problems that could have easily been avoided from developing. We hope this article informs you about studio safety and how to keep yourself healthy while in the studio.

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20 Ways to Stay Safe in the Pottery Studio - The Ceramic School

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Studio safety is key to living a long and healthy life as a potter. In our line of work, we can come into contact with many different job hazards that can cause us grief down the road. Being cautious and taking preventative measures is the best way to stay safe in the studio for the long term.

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Notes

Lithium Carbonate is the best source of lithium oxide for glazes. It is slightly soluble. It is unusual to see more than 5% lithium carbonate in glaze. Because of the low expansion of , high lithium glazes tend to shiver.

There are certain basic properties of lithium which are of interest in ceramics. Since lithium has a very small ionic radius in comparison to the other alkali metals, it has a higher field strength. Low expansion coefficients are generally imparted to ceramic compositions containing lithia. Lithium carbonate is a very strong flux (also true of lithium fluoride). In contrast, other lithium compounds may be quite refractory: lithium zirconate and lithium aluminum spinel are examples.

There is comparatively little published information on the use of lithia compounds in ceramics. Laboratory investigations indicate that small additions of lithium will react with quartz during firing and eliminate the alpha-beta quartz transition in the cooling cycle. Lithia imparts low thermal expansion coefficients to glasses and also promotes devitrification in glass systems. Smaller amounts act to smooth the glass surface.

Lithium exhibits many properties that are similar to the more common alkali metals sodium and potassium. In many respects is also shows similarities to the elements of the alkaline earth group, especially magnesium.

In addition to being soluble, lithium carbonate produces gases as it decomposes and these can cause pinholes or blisters in glazes. There are insoluble lithium frits available (e.g. Fusion F-493 has 11%) and incorporating one of them to source the Li ₂O instead is a classic application of glaze chemistry calculations (however for glazes with very high amounts of lithium, like 10%+, it will be difficult to source the Li ₂O using a frit because significant amounts will be required and this will likely oversupply the other oxides the frit brings). The resultant glaze will be more fusible and will have better clarity and fewer defects.

Related Information

Original container of Albemarle Lithium Carbonate

Original container of Rockwood Lithium Carbonate

Sourcing Li2O from spodumene instead of lithium carbonate

Lithium carbonate is now ultra-expensive. Yet the glaze on the left needs it. Spodumene has a high enoughLi ₂O concentration to be a practical source here. It also has a complex chemistry, but the other oxides it contains are those common to glazes anyway. Using my account at insight-live.com, I did the calculations and got a pretty good match in the formulas (lower section in the green boxes). Then I made 10 gram balls and did a melt flow test at 2200F (notice the long crystals in the glass pools below the runways). Not surprisingly, this recipe is very runny, that's why the tiny yellow crystals grow during cooling, they produce the gold effect this recipe is known for. The spodumene version is very similar, perhaps better. The calculated cost shown is outdated, in 2022 for us it is $17.84 vs $10.40 per kg (based on purchasing 2.5kg amounts of the materials).

Frits instead of raw zinc, lithium, barium, strontium

These materials have many issues. They can create problems in your glaze slurries (like precipitates, higher drying shrinkage), cause issues with laydown and dried surface and cause fired surface defects (like pinholes, blisters, orange peeling, crystallization). And lithium and barium have toxicity issues (as raw materials). And the lithium, barium and strontium are carbonates, that means carbon burns off during firing (with lithium, for example, 60% of its weight is lost). Yet the oxides that these materials source to the glaze melt, ZnO, , BaO and SrO can be sourced from frits. In doing that you can solve almost all the problems and get better glaze melting. Fusion Frit F 493 has 11% LI2O, F 403 has 35% BaO, F 581 has 39% SrO and FZ 16 has 15% ZnO. Of course, these frits source other oxides (but these are common in most glazes). Using glaze chemistry you can often duplicate the chemistry of a glaze while sourcing these oxides from frits.

Lithium carbonate precipitation in one gallon of glaze

This is one of the issues with using the material. These have to be screened out from time to time, if not they produce defects in fired ware. Better to employ a lithium frit to source .

Crystals found growing in a glaze containing lithium carbonate

Crystals found growing in a glaze containing 7% lithium carbonate, 7% titanium dioxide and 6% cadycal. Also had wollastonite, silica, koalin and nepheline syenite. Courtesy of Mark Rossier Pottery.

Alberta Slip using in the common lithium-tin cone 6 glaze

This is 85% Alberta Slip, 11% lithium and 4% tin fired at cone 6 in oxidation. Like the original Albany version, it has a very low thermal expansion (because of the high lithium content) and likes to shiver on many bodies.

Lithium and tin do this to an otherwise transparent dull brown Alberta Slip glaze

10% lithium carbonate and 4% tin.

Links

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Notes Lithium Carbonate is the best source of lithium oxide for glazes. It is slightly soluble. It is unusual to see more than 5% lithium carbonate in glaze. Because of the low expansion of , high lithium glazes tend to shiver. There are certain basic properties of lithium which are of interest in ceramics.

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Salt, Soda, and Wood-Fire Recipes

In this section, you’ll find flashing slip and glaze recipes to use in an atmospheric, Salt, Soda, and/or Wood firing.

Salt firing is a vapor-glazing process where salt (sodium chloride) is introduced into the kiln firebox at high temperature. The salt vaporizes, and sodium vapor combines with silica in clay surface, forming extremely hard sodium-silicate glaze.

Soda firing has been touted as modern-day nontoxic replacement for salt firing, but has proven to be much more than that. Potters have discovered that soda firing has endless exciting aesthetic possibilities rather than just being a more environmentally friendly! In the soda firing process, soda ash (sodium carbonate) in water solution, instead of salt, is sprayed into kiln at maturing temperature, and sodium vapor combines with silica in clay to form sodium-silicate glaze. Since humans first began to understand how fire hardened clay, we have been making ceramics, both in pits and in wood kilns. Now, with so many fuel options available to the potter, wood-fired kilns are more of a choice than a necessity. While wood kiln firing isn’t easy, the results are incomparable. The work in wood kilns reveals the story of the firing, with pieces showing ash deposits and the path of the flame through the kiln. In these archives, Salt, Soda, and/or Wood Firing artists share their glaze recipes and their atmospheric slip recipes

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Soda firing has been touted as modern-day nontoxic replacement for salt firing, but has proven to be much more than that. Potters have discovered that soda firing has endless exciting aesthetic possibilities rather than just being a more environmentally friendly!

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What if you could find an ever-expanding collection of hundreds and hundreds of ceramic glaze recipes fully searchable by firing temperature, atmosphere, ingredients, and more? You've found it with Ceramic Recipes, part of the Ceramic Arts Network.

Ceramic Recipes features:

Hundreds of clay, slip, and glaze recipes with full-color photos of finished results, as well as instructions on how to get the best effects

Robust search capabilities so you can find ceramic glaze recipes by firing temperature, color, surface texture, firing atmosphere, ingredient, author, or any combination of these

User-friendly upload interface to make it easy to add your own recipes to store in your account

Favorites button so you can save your favorite clay and glaze recipes to your own account

Sharing capabilities so you can share your favorite recipes with the rest of the Ceramic Recipes community

Reference articles on everything from dealing with glaze faults to the specifics of common glaze materials to the science behind surfaces

Whether you are just getting started with mixing your own glazes, or you've been developing ceramic glaze recipes for years, the Ceramic Recipes online database is a one-stop resource for finding and saving ceramic glaze recipes. Most of us have our recipes scattered around our studios on scraps of paper, but with Ceramic Recipes, they can be organized and easily accessible through a phone, tablet, or computer. So, if you are at the ceramic supplier and need ingredients for a new recipe you want to try, you can easily pull it up on your phone and determine how much you need of each using the recipe calculator function. How useful is that?

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What if you could find an ever-expanding collection of hundreds and hundreds of ceramic glaze recipes fully searchable by firing temperature, atmosphere, ingredients, and more? You've found it with Ceramic Recipes, part of the Ceramic Arts Network.

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This table suggests materials to test as possible replacements for imported and often hard to obtain items. The first column shows the product name, the second column a brief description of the product and its uses and the third column the suggested alternative.

Product

Description & Uses

Suggested Alternative (s)

Kentucky 4 and 12 Clays

A fine grained ball clay mainly used in casting bodies.

Ball Clay FX / CA1 (BA200)
or Ball Clay R (BA210)

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This table suggests materials to test as possible replacements for imported and often hard to obtain items. The first column shows the product name, the second column a brief description of the product and its uses and the third column the suggested alternative.

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Tutorial Videos

Mixing Test Batches

How to mix a test batch using the Glazy batch calculator.

Mixing & Sieving Batches

Once you've made up a batch, how can you mix and prepare it for application?

Applying Glaze to Test Tiles

Now that you've mixed and/or sieved your batch, you're ready to apply the glaze to test tiles.

Batch Sizes

Glazes "don't travel well", in other words materials, application, and firings vary from studio to studio. Even for well-known glazes, it's important to first make a few small tests. For these tests, use 50g or 100g of material and apply the test glaze to a number of different clay bodies. If a test comes out well, mix a larger batch of 1-2Kg. 1Kg is enough material to glaze small cups, 2Kg is a good amount for small bowls. These larger tests should reveal any problems with glaze suspension, application (cracking, peeling, etc.), and fired glaze defects. Once you have some nice results with 1Kg, you can finally move on to a big bucket of 5-10Kg.

Batch Calculator

The batch calculator simply multiplies each ingredient amount. It is unit-independent. In the example shown, it does not matter if we are making 2000 grams, kilograms, pounds or even tonnes of glaze.

Note that additive materials such as coloring oxides are calculated in addition to the batch amount.

In the example below, the base recipe is calculated to 1000 units (grams, pounds, whatever), while the additional materials (Tin Oxide and Yellow Iron Oxide) are added on top of 1000.

Sieves

For "natural" glazes containing large-grained materials or ashes, or in cases where homogeneity is not a concern, it's fine to use a larger screen of 60-80 mesh. But in all other cases it's good to use 120 mesh or smaller. Small mesh size is very important for glazes that contain small amounts of very important materials such as coloring oxides (e.g. cobalt and iron). But it's also important to ensure that materials are adequately broken up and mixed (such as clays).

Below you can see two tests of the same batch of glaze fired in the same kiln. The first test was applied after passing the materials three times through an 80 mesh screen. The second test is the result of passing that same glaze once more through a 120 mesh screen.

Scales

Weight measuring scales come in a wide range of types and prices. Purchasing a scale is a trade-off between cost, resolution and capacity. In general, scales that can weigh larger amounts of materials have lower resolution (e.g. 1 gram), while scales that have higher resolution (e.g. 0.01 grams) can only weigh small amounts.

For weighing small amounts of glaze materials (for example, 50 and 100 gram test batches), it is very important to use a scale that has a readability to at least 0.1 grams. (Some glaze materials such as cobalt are very strong, and a difference of even 0.1 grams in a 100 gram batch will have a noticeable impact.) Ideally, your test scale will have a capacity of over 100 grams and readability of 0.01 grams.

Note: Just because a scale has a high resolution (e.g. 0.01 grams) does not mean it has high accuracy. Price is usually a good indication of accuracy, so it's best to get the most expensive scale that you can reasonably afford.

The Ohaus Scout Pro SP4001 and SP202 digital scales during calibration. It is important to periodically calibrate your scales using accurate calibration weights.

Using a Beam Scale

For those on a budget, perhaps the most affordable solution for precise weighing of glaze materials is a triple beam scale.

Select a container to hold glaze materials and weigh it on the scale. In the example below, the container weighs 63 grams:

On the Glazy recipe page, enter the Tare Weight:

Enter the Batch Size. The batch size is unit independent. In the below example, we could be measuring 400 grams, 400 pounds, or even 400 tons of recipe material. But in this case, we are using grams. Notice that the final subtotal equals 463, which is the Tare Weight (weight of the container) plus the Batch Size.

After measuring out the first ingredient, EPK, our scale should show 251 (63 grams container weight plus 188 grams of EPK):

After measuring out all of the ingredients for this batch, the scale should read 463 (63 gram container plus 400 gram batch):

Mixing Test Glazes

It's important to wear a well-fitting, NIOSH certified mask whenever mixing ceramic materials. All materials should be handled in well-ventilated area to avoid the risk of inhalation. For more information about the hazards of mixing ceramic materials, see the article Studio Dust by Mark Goldbergopen in new window .

For test glazes, try to find re-useable containers that fit your seives like these plastic restaurant soup bowls with lids. Glaze name & recipe can be written on the container with permanent marker.

Carefully measure out each ingredient into the bowl, placing into separate piles so that any extra material can be easily removed. The measurement displayed on the scale should match the "Subtotal" column in the Glazy Batch Calculator.

Dry mix the ingredients with a spoon until well dispersed.

For 100 grams of material, add about 50-60ml of water (less if your glaze has little or no clay).

Wait a few minutes until the water has thoroughly soaked the materials, then stir. Glaze should be fairly thick, do not add too much water as you will be adding more as you go along.

Use a fairly stiff rib to scrape the glaze through the sieve.

The first pass takes the most work as the clays are broken apart.

Try not to lose any material, especially if preparing for volumetric blending. Use a water sprayer to clean the container, spoon, and sieve after each pass. But don't add too much water.

Pass the glaze through the sieve two or three times. After the final pass, the glaze should be creamy without any large grains or lumps.

Now you can slowly mix in water and dip your test tiles. Flat test tiles require the least amount of glaze.

Test tiles can be dipped multiple times in order to see the result of glaze thickness. It is best to double-dip the side of a test tile rather than the top so that the two different glaze thicknesses do not run into one another.

Record as much information as you can on each test tile. On this tile, the type of clay has been stamped, while glaze information was written with an underglaze pencil. After firing, a permanent marker was used to record the firing date and actual cone reached.

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How to mix a test batch using the Glazy batch calculator. Once you've made up a batch, how can you mix and prepare it for application? Now that you've mixed and/or sieved your batch, you're ready to apply the glaze to test tiles.

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What are cones?

Firing ceramics in a kiln is a bit like cooking a pizza in the oven. As with Italian wood-fired stoves, you could set your oven on very high heat and cook the pizza in just four minutes. Or you could cook the pizza for a longer amount of time at lower heat. Either way, you'll end up with edible pizza.

Pyrometric cones are a measurement of the total amount of heatwork. Heatwork is the combination of time and temperature. We can say that two pizzas received a similar amount of heatwork if they are both fully cooked, even if they were cooked at different temperatures for different durations of time. Similarly, we can say that two ceramic vases were fired to a certain cone (e.g. similar amount of heatwork) even if the firings were different in temperature & time.

It's important to note that firings are often uneven: a kiln may have cool and hot spots, and the difference in temperature may be one or more cones. Just because a cone has fallen doesn't mean the entire kiln (including the ceramics and kiln furniture) has also reached that cone temperature. So it's a good idea to sometimes place extra cones throughout the kiln to determine if the firing is even.

For more information on cones, see the excellent Digitalfire article as well as Orton's .

Setting & Reading Cones
The quantity of cones and cone packs as well as their arrangement and placement vary from potter to potter, kiln to kiln. The following is only one approach.
There are a number of different cone manufacturers. Each brand has unique cone formulations and firing characteristics. Cone numbers between brands may be quite different, for instance the Chinese "Seger" cone 9 is approximately Orton cone 12. Even when cone numbers between brands are rated for the same temperature, actual firing behaviour may be quite different. Glazy recommends using Orton cones as they seem to be the most reliable and accurate.
Length of large cones above cone plaque. Breaking apart pairs of Orton cones using a cylindrical support.
According to Orton:
Wet cone packs can explode. Make your packs in advance or poke holes into the pack to let steam to escape. After flattening a coil of clay, push cones downwards so that the angle is identical with a cone placed directly on the flat surface.

"Large Cones are normally mounted so exactly 2" of the cone is exposed above the top of the cone plaque or clay pat. Small Cones are mounted so that 15/16" of the cone is exposed above the top of the plaque or pat."

A cone pack after firing. In this firing, once cone 9 fell to 5 o'clock the kiln was intentionally stalled. Even though the temperature did not rise, cone 10 completely fell after about one hour. Cones measure heatwork, the effect of both temperature and time. Inexpensive Chinese cones. Cones 7 and 9 are down, but cone 8 is still standing. The entire box of cones should be thrown away. But which cone is defective, 8 or 9? Compared to the cost of a firing and the work inside, the cost of cones is negligible. Buy the most reliable cones you can find. Viewing low-temperature cones in the kiln at about 900°C. Cone 010 is bending, while 08, 1, and 3 have not moved. It's advisable to place cone packs at the top and bottom of your kiln in order to understand and control temperature differences while firing. Warning: Prolonged or cumulative long-term exposure to infrared and ultraviolet light can seriously damage your eyes. For mid and high fire, a "boat" is made to catch low-temperature cones. This boat is a folded slab. Sunglasses that only filter ultraviolet light are NOT sufficient.
Measure your cones and memorize how deeply they should be mounted.

This cone pack is for an Orton cone 10 firing.

The guide cone 9 will alert us when we are close to temperature. The guard cone 11 will let us know if we are beginning to overfire.
#5 welding goggles and 2000 lumens LED flashlight.
While more expensive, pre-made cone plaques and self-supporting cones eliminate height and angle inconsistencies.

The can be used to determine the degree of deformation for Orton cones.

Download PDF chart of Orton Cone positions: Color (566.2 KB) A4 Black & White (78.2 KB)

Viewing Cones

ANSI-compliant infrared and ultraviolet eye-protection glasses are a must when viewing inside the kiln at high temperatures.

For more information, see

There are many tricks for seeing cones more clearly inside the kiln.

The simplest method is using a high-intensity LED flashlight with an output of at least 400 lumens and a focused beam.

Temperature Equivalent Charts for Cones

References:

Orton Pyrometric Cones Celsius (°C)

Orton Pyrometric Cones Fahrenheit (°F)

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Firing ceramics in a kiln is a bit like cooking a pizza in the oven. As with Italian wood-fired stoves, you could set your oven on very high heat and cook the pizza in just four minutes. Or you could cook the pizza for a longer amount of time at lower heat.

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Line Blends

Line blends are a useful tool for comparing two different recipes. Often, the two recipes are different glazes. For instance, you can blend two different celadon glazes in different proportions to create a new celadon recipe. Line blends are also commonly used for testing additions of coloring oxides, for instance the effect of incrementally adding iron oxide to a clear glaze.

The range of the line blend is arbitrary- you can start each variable from 0% and go up to 100% or you could choose any range in-between.

To illustrate a line blend, here is a sample using two RGB colors blending by opacity. If you already know the result of the outlying 100% blends, you could remove them from the test. However, each firing is different and it's usually good to test the 100% blends regardless.

You could mix each test in a line blend individually, but a much less time-consuming method is to only make the left and right-most solutions. Using a syringe, you can easily create each mixed blend.

Volumetric Blending

Ian Currie popularized volumetric blending. ( See his article here.)

First, mix the same weight of each glaze you will be blending. Second, add some water to the glazes and sieve thoroughly. Third, add water to each glaze so that their volumes are equal. Now the two glazes are ready for blending.

Volumetric Blending in a Syringe

Below is an illustration of the blends in a 20ml syringe. If your test tiles are relatively small (7cm square) and flat, 20ml of solution should be enough for two coats of dipped glaze.

As you can see, for 10% increments using a 20ml syringe we need at least 20+18+16+14+12+10+8+6+4+2 = 110ml of each 100% recipe. Preparing 100 grams of glaze material for each glaze should be sufficient.

Each time before you take glaze into the syringe, be sure to re-mix the glaze and confirm it has not settled.

Line Blend Example

As a real-world example, let's add red iron oxide the a reduction-fired clear glaze Leach 4321. We will create a line blend from 0% to 10% additional Red Iron Oxide in 1% increments. This is sufficient to see the gradual transition from clear to blue-green celadon (0.5-1%), light green celadon (2%), dark green celadon (3-4%), amber (5-6%), and tenmoku (7-10%).

First, two glaze batches of 100g are prepared. The first is just Leach 4321, while the second is Leach 4321 + 10% Red Iron Oxide.

Second, a syringe is used to mix the two glazes in increments. By using a 30ml syringe there is extra room in the syringe for drawing in air, making it easier to mix the glazes.

On the back of each test tile is written the glaze information. The test tile is dipped once in the glaze and then dipped again at an angle in order to cover half of the tile. The final line blend tests show a nice progression from 0% to 10% red iron oxide.

Here is the line blend after firing to Orton cone 10 in a reduction atmosphere. The tests reveal a range of interesting glazes.

The results of these tests can be viewed in Glazy:

Leach 4321
Leach 4321 + 1% Red Iron Oxide
Leach 4321 + 2% Red Iron Oxide
Leach 4321 + 3% Red Iron Oxide
Leach 4321 + 4% Red Iron Oxide
Leach 4321 + 5% Red Iron Oxide
Leach 4321 + 6% Red Iron Oxide
Leach 4321 + 7% Red Iron Oxide
Leach 4321 + 8% Red Iron Oxide
Leach 4321 + 9% Red Iron Oxide
Leach 4321 + 10% Red Iron Oxide

Care should be taken when specifying the parameters of a line blend. For example, here is the result of a similar line blend created with Leach 4321 and cobalt oxide added.

As you can see, at 1% cobalt oxide the glaze is already a deep blue. Cobalt is a very strong oxide! It would have been more interesting to add cobalt in just 0.1% increments.

As you can see, at +0.1% cobalt oxide, the glaze color is already greatly affected. This test also highlights the need for sensitive, accurate scales when dealing with small batches of glaze.

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Line Blends Line blends are a useful tool for comparing two different recipes. Often, the two recipes are different glazes. For instance, you can blend two different celadon glazes in different proportions to create a new celadon recipe.

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Five Base Ingredients

The good news is that for cone 5-7 firings, you can do almost everything with 5 ingredients in the glaze base. These are the ingredients you'll need to buy in larger amounts, so simplifying the base recipe allows you to have a selection of glazes without committing too much money or storage space.

The five ingredients I would recommend are:

Each of these has a specific function in the glaze, and a lot of the other ingredient options will perform a very similar function with slight changes in the underlying chemistry. There can be very good reasons to pick one ingredient over another, so this selection of ingredients will rule out certain types of glaze or specific glaze effects. However, these five are a great starting point and will give a very wide range of glazes.

My knowledge of what each material contributes and how glazes can be easily altered to achieve specific chemistry came from the Ceramic Materials Workshop Understanding Glazes class, which I would highly recommend if you want to learn more. You can use offer code oldforgecmw for 25% off the Cone 6 course, which is an excellent starting point for getting deeper into understand what each ingredient does.

Colourants

There's a lot less overlap here, as each colourant has a fairly unique colour palette. The good news is that they generally don't get added to the recipes at a high percentage, so you can buy the smallest amount of each one of the colourants needed for the recipes you want to try and it shouldn't be prohibitively expensive. (US / UK)

The main colourants I'd recommend starting with are:

Titanium (white/opacifier)

Cobalt Carbonate (mainly blue)

Copper Carbonate (mainly green)

Red Iron Oxide (mainly red/brown)

Manganese Dioxide (mainly orange/red)

Chromium Oxide (mainly green)

Tin Oxide (white, but pink/purple with Chromium)

Zirconium (white/opacifier)

Stains (these are premade mixes of colourants that should predictably give a specific colour, but will be more expensive than the oxide/carbonate equivalent)

There are other colourants, and other versions of the colorants above (e.g. cobalt oxide vs cobalt carbonate) but these are the ones I'd suggest starting with.

Not a colourant, but often included with them is Bentonite (US / UK). It's a type of clay that is used to keep the other ingredients suspended in the mix. It's generally worth adding 1-2% to most glazes to improve the mix and application properties of the glaze without affecting the chemistry much.

Equipment

You don't need much, but there are a few essential and a few useful pieces of equipment.

PPE - There are quite a few glaze ingredients you don't want to ingest and you really don't want to be inhaling any of them. So a good filter mask (US / UK) is a must for the long term health of your lungs, and eye protection and gloves are sensible additional precautions.

Scales - You need to be able to measure ingredients, and this is done by weight. Scales will come with two numbers, the maximum weight they can measure and the precision they measure it with. When looking at cheap scales you'll generally find that there are 3 ranges and all of them are useful for different batch amounts

I would suggest the 500g version if you only want to do tests and very small batches to start as the extra precision is very useful for small amounts of colourants.

Containers - If you're in the UK, I HIGHLY recommend these 400ml beakers from Wilko. They're cheap, a perfect size for glaze tests, seal really well, and are easy to clean. But any container will work, and just saving plastic food containers is a good starting point for mixing tests.

Sieve - These come in a range of sizes and meshes, but I'd suggest getting a small 80 mesh sieve (US / UK). An alternative is getting an immersion blender as they mix aggressively enough that sieving is not generally required.

How to Mix a Glaze

Following a glaze recipe is incredibly easy. The general format is to have a base recipe that adds up to 100%, then colourants are added to it. (This is a slightly simplified view of glaze chemistry as different colourants will affect the behaviour of the base recipe differently, but for colourants at a couple of percent it won't be a big effect.)

The basic steps to mixing a glaze are:

1. Decide how much you want to mix (I'd recommend starting with 100g base as a very convenient size for a test) and multiply the ingredients (Glazy will do this automatically for you by changing the number in the 'Batch' box under the recipe).

2. Weigh out the water (I would suggest 90% of the base weight as a starting point, it's easier to add more than remove it)

3. Get your ingredients out. I put them all to one side of the bench at the start and move them across as I add them, that way if I get interrupted halfway through I know exactly where I was.

4. Put on your mask, gloves, goggles, etc.

5. Weigh out each ingredient and add them to a dry container.

6. Mix the dry ingredients. I highly recommend some amount of dry mixing before adding the ingredients to the water if you're adding bentonite, as it will clump if not dispersed before being added to water and becomes far more difficult to deal with. Do this very gently to avoid kicking up dust, and it's always a good idea to vent the space afterwards (after wiping surfaces with a wet cloth, but before removing the mask) to remove any dust that did become airborne.

7. Add the dry ingredients to the water. Doing it this way around means no dry clumps at the bottom of the container

8. Mix thoroughly. If you have an immersion blender this can be a very quick way to mix well enough to avoid having to sieve afterwards, but if not then pass through a 60-100 mesh sieve to make sure there are no lumps.

9. Apply to test tiles. I would always recommend starting with small batches of glaze and testing on test tiles or smaller pieces, as there are so many variables and so few guarantees in glazing. I would also recommend weighing the glaze application on the test tiles as it's the easiest way to know how much glaze there is on a tile. The majority of test tiles I see where people are trying my glazes and not getting the results they want, the application is far too thin. If you have weighed the application then you'll have a starting point for adjusting the application for subsequent tests.

10. Fire. I recommend putting the test tiles on a scrap tile of clay in case they run. These recipes will work best around cone 6. If you're not sure what cone your kiln is firing to, the best way to be sure is to use Orton Cones to check rather than using the temperature from the kiln controller.

Food Safe Glazes (See FAQ Below)

This is a simple glossy clear base, that should work well with colourants to make a solid glossy colour. It is fairly static, so won't flow as much as some of the other recipes.

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First Five Ingredients - Where to start with Glaze Making - Old Forge Creations

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Glaze making is an incredibly straightforward process but knowing where to start is far trickier. There are hundreds of available ingredients, and it's not clear which ones you should buy first.

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All Recipe Codes All Recipes

Insight-Live Shares (also referencing this recipe)

These add technical detail, development info, variations and improvements.

Modified: 2022-03-28 21:08:56

A cone 10R dolomite matte having a pleasant silky surface, it does not cutlery mark, stain or craze on common bodies

Notes

A standard Plainsman Clays cone 10R dolomite matte glaze used for many years. Colorants and opacifiers can be added to create a wide range of beautiful classic earthy reduction effects. The bamboo effect, made by the addition of 3.5 rutile and 10 Zircopax, is probably the most popular.

Many dolomite (or talc) matte glazes do not have a proper chemistry balance and do not melt to a stable glass; crazing, cutlery marking and staining are common problems. This one, by contrast, has a very silky surface yet exhibits none of these problems. An alternative recipe (but very similar chemistry) using Ravenscrag Slip is also available.

If you do not have Gerstley Borate or Wollastonite it is pretty easy to alter the recipe to source CaO calcium carbonate (instead of wollastonite) and from a frit instead of GB.

Click the link above to see more detail about this recipe at digitalfire.com.

Related Information

A tin oxide addition improves the visual character of a cone 10R bamboo

This is the G2571A base dolomite matte recipe. The specimen on the left adds 4% tin and 1% iron oxide. The one on the right has 4% tin oxide and 0.5% iron oxide.

G2571A bamboo matte on the left is better, it does not stain

These mugs are Plainsman H443. The bamboo glaze on the left (A) has 3.5% rutile and 10% zircopax added to the base G2571A dolomite matte. The one on the right (B) has the same addition but in a base having slightly less MgO and slightly more KNaO. B stains badly (as can be seen from the felt marker residue that could not be removed using lacquer thinner). Why does A stain only slightly? It has an additional 4% Gerstley Borate (GB). GB is a powerful flux that develops the glass better, making the surface more silky. The differences in the recipe provide another advantage: (A) has a much lower thermal expansion and is less likely to craze.

Two G2571A Bamboo versions: With iron, rutile-zircopax

These mugs are Plainsman H450 fired at cone 10R. Both have a black engobe (L3954N) applied to the insides and half way down the outside during leather hard stage (the insides are glazed with Ravenscrag silky matte and G1947U over the black engobe). The bamboo glazes can thus be seen over the black (upper half) and the raw buff body (lower). The bamboo glaze on the left has 1% iron added to the base G2571A recipe. The one on the right has 3.5% powdered rutile and 10% zircopax added.

G2571 Cone 10R silky matte glazed mug

The inside is pure Ravenscrag Slip. The clay is Plainsman H550.

Adding Zircopax to G2571A dolomite matte

On the left: G2571A dolomite matte fired at cone 10R. Right: 10% Zircopax has been added. Both are on a buff stoneware (H550 from Plainsman Clays).

G2571A at cone 10R with a cobalt and chrome addition

This is G2571A cone 10R dolomite matte glaze with added 1% cobalt oxide, 0.2% chrome oxide. The porcelain is Plainsman P700, the inside glaze is a Ravenscrag Slip clear. This base is very resistant to crazing on most bodies and it does not cutlery mark or stain. It also has very good application properties.

The titanium/stain mechanism at cone 10R

These are porcelain and stoneware mugs. The glaze is G2571D (based on the fritted G2571B version of G2571A). This project started with calculations to source boron from a frit (instead of Gerstley Borate), MgO from talc and a frit (instead of dolomite). These moves enabled eliminating raw silica from the recipe. This produced a finer silky texture and better melt fluidity (for hosting colors). Adding rutile and zircopax produced a great bamboo. But what about variegating using titanium instead of rutile (it contains no iron so colors should be brighter)? Look what happens with this red stain! The titanium has done it's job even a little too well (creating a slightly more abrasive surface). Cobalt and titanium also worked. Imagine if other stains would produce dramatic results like this, each with the amount of titanium tuned to it!

Multiple kinds of glaze variegation

The inside glaze of this cone 10 reduction fired mug is a base transparent glossy, G1947U. It has no additives to color, opacify or variegate it. That being said, the speckled body is making for a more interesting aesthetic on that inside surface. The outside glaze is a far different story. It is a base - a silky matte, G2571A. But it has additions of 3% titanium dioxide and 6% Mason 6021 red stain (this version is numbered G2571D). Of course the red coloration is from the stain. But the titanium is making the visual magic here, it is both an opacifier and a variegator. It is clearly producing phase changes and crystallization. One of the glass phases is redder and more transparent (the brighter red spots). Another phase is a much lighter opaque pink.

G2571A at 1.75 specific gravity still works, but goes on very, very thick

Do not use this glaze unless the specific gravity is optimal. For bisque ware, that will be about 1.43-1.45 (and flocculated to gel slightly). If the SG is too high it will go on too thick. If it is too low, it will shrink too much during drying (and likely cause crawling).

The effect a cone 10R iron stoneware imposes on G2571A matte glaze

This bamboo glaze (made by adding 4% tin and 1% iron oxide (left) and 0.5% iron oxide (right) to the G2571A base recipe) amplifies the iron speckle in the body beneath (Plainsman H443). Unfortunately this looks good and but is not very functional. The body is quite porous (5% water absorption), this is necessary for the mottled brown visual effect.

15 inch reduction fired bowl by Tony Hansen

Made in 1982. Clay is Plainsman H443 fired at cone 10R. Glaze is G2571A with 0.25% chrome oxide, 1.0% cobalt oxide and 0.25% manganese granular.

Duplicating the G2571A dolomite matte using a Ravenscrag Slip based recipe

GR10-J Ravenscrag silky matte (right) and G2571A matte (left) on a dark burning iron speckled stoneware at cone 10R. The surfaces have identical feel (the chemistries are very close). The former fires a little darker color because of the iron contributed by the Ravenscrag Slip.

Links

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All Recipe Codes All Recipes Insight-Live Shares (also referencing this recipe) These add technical detail, development info, variations and improvements. Modified: 2022-03-28 21:08:56 A cone 10R dolomite matte having a pleasant silky surface, it does not cutlery mark, stain or craze on common bodies Notes A standard Plainsman Clays cone 10R dolomite matte glaze used for many years.

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All Articles A Low Cost Tester of Glaze Melt Fluidity
A One-speed Lab or Studio Slurry Mixer
A Textbook Cone 6 Matte Glaze With Problems
Adjusting Glaze Expansion by Calculation to Solve Shivering
Alberta Slip, 20 Years of Substitution for Albany Slip
An Overview of Ceramic Stains
Are You in Control of Your Production Process?
Are Your Glazes Food Safe or are They Leachable?
Attack on Glass: Corrosion Attack Mechanisms
Ball Milling Glazes, Bodies, Engobes
Binders for Ceramic Bodies
Bringing Out the Big Guns in Craze Control: MgO (G1215U)
Ceramic Glazes Today
Ceramic Material Nomenclature
Ceramic Tile Clay Body Formulation
Changing Our View of Glazes
Chemistry vs. Matrix Blending to Create Glazes from Native Materials
Concentrate on One Good Glaze
Cone 6 Floating Blue Glaze Recipe
Copper Red Glazes
Crazing and Bacteria: Is There a Hazard?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms
Creating a Non-Glaze Ceramic Slip or Engobe
Creating Your Own Budget Glaze
Crystal Glazes: Understanding the Process and Materials
Deflocculants: A Detailed Overview
Demonstrating Glaze Fit Issues to Students
Diagnosing a Casting Problem at a Sanitaryware Plant
Drying Ceramics Without Cracks
Duplicating Albany Slip
Duplicating AP Green Fireclay
Electric Hobby Kilns: What You Need to Know
Fighting the Glaze Dragon
Firing Clay Test Bars
Firing: What Happens to Ceramic Ware in a Firing Kiln
First You See It Then You Don't: Raku Glaze Stability
Fixing a glaze that does not stay in suspension
Formulating a body using clays native to your area
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
G1214M Cone 5-7 20x5 Glossy Base Glaze
G1214W Cone 6 Transparent Base Glaze
G1214Z Cone 6 Matte Base Glaze
G1916M Cone 06-04 Base Glaze
G1947U/G2571A Cone 10/10R Base Matte/Glossy Glazes
Getting the Glaze Color You Want: Working With Stains
Glaze and Body Pigments and Stains in the Ceramic Tile Industry
Glaze Chemistry Basics - Formula, Analysis, Mole%, Unity
Glaze chemistry using a frit of approximate analysis
Glaze Recipes: Formulate Your Own Instead
Glaze Types, Formulation and Application in the Tile Industry
Having Your Glaze Tested for Toxic Metal Release
High Gloss Glazes
How a Material Chemical Analysis is Done
How desktop INSIGHT Deals With Unity, LOI and Formula Weight
How to Find and Test Your Own Native Clays
I've Always Done It This Way!
Inkjet Decoration of Ceramic Tiles
Is Your Fired Ware Safe?
Leaching Cone 6 Glaze Case Study
Limit Formulas and Target Formulas
Low Budget Testing of the Raw and Fired Properties of a Glaze
Low Fire White Talc Casting Body Recipe
Make Your Own Ball Mill Stand
Making Glaze Testing Cones
Monoporosa or Single Fired Wall Tiles
Organic Matter in Clays: Detailed Overview
Outdoor Weather Resistant Ceramics
Painting Glazes Rather Than Dipping or Spraying
Particle Size Distribution of Ceramic Powders
Porcelain Tile, Vitrified Tile
Rationalizing Conflicting Opinions About Plasticity
Ravenscrag Slip is Born
Recylcing Scrap Clay
Reducing the Firing Temperature of a Glaze From Cone 10 to 6
Simple Physical Testing of Clays
Single Fire Glazing
Soluble Salts in Minerals: Detailed Overview
Some Keys to Dealing With Firing Cracks
Stoneware Casting Body Recipes
Substituting Cornwall Stone
Super-Refined Terra Sigillata
The Chemistry, Physics and Manufacturing of Glaze Frits
The Effect of Glaze Fit on Fired Ware Strength
The Four Levels on Which to View Ceramic Glazes
The Majolica Earthenware Process
The Potter's Prayer
The Right Chemistry for a Cone 6 MgO Matte
The Trials of Being the Only Technical Person in the Club
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Toxicity of Firebricks Used in Ovens
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Understanding Ceramic Oxides
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Unwanted Crystallization in a Cone 6 Glaze
Volcanic Ash
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What is a Mole, Checking Out the Mole
What is the Glaze Dragon?
Where do I start in understanding glazes?
Why Textbook Glazes Are So Difficult
Description

The process we used to improve the 20x5 base cone 6 glaze recipe

Article

I love to use the Glaze Dragon as a symbol of the attitudes that prevent us from getting control of our glazes and our addiction to the 'roulette wheel' approach to finding glazes. The dragon wants us to think glaze science is a 'mystery', that existing recipes were dropped from heaven and questioning or adjusting them is blasphemy. The advent of the internet has actually made us worse, we're furiously trafficking in more recipes that don't travel well.

Decades of glossy magazines have taught us that 'appearance is everything'. Schools still crank out generations of ceramists with numbed consciences regarding their functional accountability to customers. At conferences we've argued about craft and art and addressed the politics of ceramics. But the closest we ever seem to come to understanding glazes is learning application methods. It is true, many authors and teachers have been singing the 'learn-your-materials' song. But those studying materials feel ill-equipped to create balanced, fitted, strong, color compatible glazes, opening the kiln is still like pulling the handle on a slot machine.

The key to creating good recipes is the marriage of material and oxide knowledge. Oxides? Fired glazes are built out of them. They are a universal language of glazes. The kiln decomposes ceramic materials into their oxide building blocks and reassembles them into the fired glaze. Oxide know-how has been out there all along and computer users have rediscovered it. These people have not been on the roller coaster, they have been making really exciting things happen in the studio and on the factory floor, learning from their mistakes as never before. And the Internet has allowed them to find each other and rejoice in not being as alone as they thought.

But many questions still remain. The most asked question I hear is: "Do you have a good cone 6 glaze?" It is asked so often because so many non-satisfactory answers have been given in the past. What we need to answer it well is a 'attitude transplant' about what a good glaze is and how to get it. I would like to demonstrate how we can view materials as both powders with a physical presence that shapes the properties of the glaze slurry and also as 'oxide warehouses' that supply building blocks to the fired glass.

After enough failed 'affairs' with textbook or internet recipes you can lose your ability to recognize true glaze quality. It is much more than simple visual character. A good recipe is:

Reliable, stable, and predictable. Its chemistry is balanced so that firing it a little slower or faster, lower or higher, applied thicker or thinner makes minimal difference and still is predictable. It offers the true economy of quality materials.

It works with a variety of stains and has associated documentation about what colors it does not work with, why, and what to do about it.

It has maximum resistance to leaching so you don't poison your customers.

It applies evenly without drips or cracking even on very dense bisque ware and fires without a tendency to blister or crawl. It does not settle hard in the bucket and it does not gel or powder off excessively.

It fires to a hard and durable surface.

It does not pinhole, crawl, or blister.

Poor glaze fit dramatically weakens ceramic ware. Thus it would have a relatively low thermal expansion so it not only does not craze on the intended body(s) but fits well so it strengthens ware.

It offers good transparency not only for its own use but as a clean starting point for other glazes.

It employs easy-to-get materials whose chemistry is published by the manufacturer or distributor(s).

You can easily adjust its melting temperature, expansion, gloss, etc.

Rationalizing a Cone 6 Glaze

How many textbook glazes have you found that could withstand this scrutiny? I've had ones that looked good but satisfied almost none of these requirements! Remember a fundamental point: The key to creating good recipes is the marriage of material and oxide knowledge. It would be very difficult indeed to meet the above requirements using a material-blending approach. It would be impossible to chance upon them by mixing recipes! It is imperative to look at the fired glaze as a formula. What is a formula? A formula compares the numbers of oxide molecules in the fired glaze. Oxides tend to have predictable effects.

You might respond: "That's too much trouble, it is all a matter of faith and trust anyway, just give me the glaze recipe!" But the Potter's Prayer is not enough, ethics and accountability are involved. Other's materials are different than mine, as is their clay, process, firing, taste, and type of ware. Someone's poor implementation or misapplication of my recipe could produce weak, difficult-to-clean, crazed, shivered, leached ware that hurts the reputation of the ceramic community, could injure people physically, and makes me partly accountable for the technical quality of their ware! Ethically I should understand and document a recipe before handing it out to prove that I am conscientious and willing to field questions to help users adapt. Borrowing recipes from others without being willing to adjust or question them is looking more and more like taking someone else's prescription.

A New Glaze is Born

Let's try to create and test glaze recipe that addresses the above requirements. I'll leave the trial and error additions of colorants, opacifiers, specking agents and variegators to you. First, consider this limit chart for cone 6 non-leaded stoneware glazes.

This chart is not a boundary waiting to be proven invalid, it is simply a recommendation of the ceramic industry. Formulas within these ranges present the least problems and tend to test well for leaching and hardness.

Now lets talk about the oxides in the above limit chart. As we do so don't think about the powdered materials you use to mix up the glaze batch, imagine being able to look at the fired glaze under a microscope powerful enough to reveal the oxide structure. I will consider them in the order they can most easily be supplied from parent materials.

Boron is a low melting glass, it is like silica on steroids, it is a flux and a glass. It is possible to make a cone 6 glaze without boron but it won't flow nearly as well and it will tend craze. Lots of cone 6 glazes have way too much boron, some employing Gerstley Borate to supply as much as all the other fluxes combined. Not good, it should be one third of that. Why? Durability, solubility and reversal of the thermal expansion influence. Like steroids, use it when appropriate and in the right amounts only! I get very good melt fluidity when B ₂O ₃ comprises about 25% of the fluxes. However chrome-tin colors tend to start failing if the boron is more than one third of the CaO amount, more on this later.

A no-alumina boron frit is perfect to source B ₂O ₃ because we can supply lots of alumina from kaolin, giving the glaze good slurry properties. About 25% Frit 3134 will give us the needed boron. How do I know that? A glaze chemistry program will show you the makeup of the frit, let you select which oxide to supply and specify how much. It then calculates the amount of frit needed.

CaO

CaO is a strong flux at cone 10 but not as much so at cone 6. But having some B ₂O ₃ around can really encourage CaO to flow better. Likewise the presence of sodium and potassium can turn CaO into a much more active flux (melter). We need CaO as high as possible to make the glaze work with chrome-tin colors, so I would like to approach the maximum recommended in the limit formula. However CaO can really tend to form either calcium-silicate or calcium-borate crystals on cooling if oversupplied. This is a bit of a dilemma.

To get around 0.55 formula units of CaO (of a total of 1.0) we need to top up the CaO already supplied by the frit. This will take 10% of my favorite calcium mineral, Wollastonite. It is much better quality than whiting, contains finely dispersed , and it does not form gases of decomposition.

As noted above, these oxides are a good choice to round out the fluxes to a total of 1 (unity formulas are adjusted so the fluxes total 1). and behave in a similar manner and melt well at cone 6 to encourage bright colors. I chose to use a clean and consistent feldspar named Kona F-4, 15% is needed. The feldspar also brings some alumina and silica with it.

An interesting part of supplying this on the computer is that the feldspar also sources CaO so you have to go back and adjust the Wollastonite again to restore CaO to 0.6.

Al ₂O ₃ gives the glaze melt body, stiffens it to keep it from running off the ware, even over a range of temperatures. The stiff melt also prevents the growth of crystals that disrupt smooth glaze surfaces and cloud transparents, we want that in a base glaze. Alumina lowers glaze thermal expansion very significantly and is a key to glaze hardness and resistance to leaching. Alumina and boron melt together very well. Like SiO ₂, you want as much alumina as a glaze will take and still melt well (you need good reason to under supply i.e. non-functional crystalline glazes). High Al ₂O ₃ usually means a matte glaze, but not if there is significant B ₂O ₃ and SiO ₂ glass formers around.

Boron glazes can take a lot of Al ₂O ₃, the above chart claims 0.65 parts (compared to around 0.4 for non-boron glazes). Tests I have done show that with the above amount of boron a glaze in this system will comfortably take 0.35 alumina, melt very well and prevent crystal growth. By 'melts well' I mean it has fired hardness, minimal bubble population, smooth hard surface, and good melt flow.

Kaolin supplies Al ₂O ₃ and it produces a glaze slurry that gels, applies evenly to ware, and dries hard. This is a match made in heaven, the more kaolin a we can employ the better. What kind of kaolin? I prefer EP Kaolin because it is clean, plastic, and flocculates and gels the glaze so it applies without drips, even on dense bisque ware.

Like alumina, silica has many beneficial effects on the fired glass. It reduces thermal expansion and increases glaze hardness; the more a glaze can tolerate the better, the limit formula above recommends up to 4.7. It is true that too much will compromise matteness or raise the melting temperature, but it is surprising how many glazes will take plenty of silica without any trouble. For example, I ran many tests with around 2.5 parts SiO ₂ thinking that it would not melt well with more. Then I added a full 10% silica (the equivalent for going from 2.5 formula to 3.0) and it worked perfectly, completely solving a crazing problem on a low silica porcelain I use. It is possible this recipe will tolerate even more.

The Calculations

Classic glaze chemistry that have been around since early this century but we just never bothered. Now glaze chemistry software makes it easy to do them and we are figuring out new ways to apply them.

After supplying each of the above oxides from the indicated materials I juggled material amounts to achieve 5% roundoffs. This held all the oxide amounts fairly close to target (except that CaO is a little over the target).

Here is the recipe:

Below there is link to this recipe in the recipe area of this site.

Now please remember, I am not promoting this recipe as the end-all of cone 6 functional base glazes. This one is part of a larger project centered on the G1214M recipe. I am promoting a way of thinking. Take this recipe, understand it, adjust it, make it work for you. For example:

Add more SiO₂ or Al₂O₃ if it melts well for you, reduce if it does not.

Reduce the B₂O₃ for CaO if you need to use chrome-tin colors.

Reduce the SiO₂ and increase the CaO to get a matte.

Add opacifiers, colorants, variegators, specking agents to create an infinite number of effects.

By the way, I found that this recipe worked well with equal parts by weight of water and powder to give a specific gravity of 1.45.

Testing Your Glaze

Mention the idea of testing a glaze and 99% of us think in terms of dipping a test tile and firing it to see how it looks. But testing should consider far more. You should test slurry properties, application properties, devitrification, clarity, crawling, stain compatibility, leaching, hardness, cutlery marking, crazing/shivering, reaction with solubles, melt flow, firing volatility, and for general functional use.

Oxide Knowledge, Electronic Textbooks and the Net

It is true, oxides and formulas can seem intimidating at first. But consider: I can list the oxides on the fingers of my hands and they have predictable behavior. Compare this with thousands of materials whose effects in recipes are much more difficult to predict (there is no such things a 'material limit recipes'). Perhaps you wonder where a person might learn about this 'predictable behavior' of oxides. It does tend to be pretty sparse in textbooks. The oxides area of this site is an excellent place to start.

Crazing

It is possible that you need to move still further to stop crazing on your clay body, especially if it is very low in silica. We suggest increasing B ₂O ₃ slightly and then increasing Al ₂O ₃. Or you may simply be able to add silica. In serious cases of crazing the magic oxide is MgO, increasing at at the expense of K ₂O and Na ₂ O will dramatically reduce the expansion. MgO does not melt as well at middle temperature but we have found the diversifying the fluxes and increasing the boron a little will make room for as much MgO as you need. Here is our G1215M recipe. Although the materials in the recipe are quite different, the chemistry is very similar. The small amount of zinc should not be a problem for most, but if it is you can leave it out and see if it still melts enough, if not add a little more frit. You can try increasing the kaolin further to drop expansion. Note that this recipe does not total 100.

As of Dec 2002 we have released a new low expansion base glaze numbered G1215U. It turns out that substituting MgO for other fluxes is by far the most effective way to reduce glaze thermal expansion. Fusion frit F69 or Ferro 3249 are the magic behind this type of approach (Frit 3249 contains a little CaO in addition to the MgO). These high magnesia frits melt much better than any natural MgO source and they do not produce gases during decomposition. Here is the recipes we are working with now:

or using Frit F69:

Because of high MgO this glaze is hostile to the development of color in Chrome Tin pink stains. It thus makes sense to add 1-2 percent zinc to make it work better with oranges and browns. We have tried it with about 20 other Mason stain and it works well with all of them (including manganese alumina pink, lavender and yellows).

Color Problems

This formula does not work well with chrome tin pink colors. To make it work you must reduce the boron and increase the calcia until it does. For the brightest pinks you may have to tolerate an increase in thermal expansion and another clay body higher in silica may have to be used to prevent crazing.

Since Frit 3134 and equivalents soften very early it is important that as much of the gases of decomposition from the body are expelled as possible before the frit melts and flows too much. If you get pinholing or blistering, try slowing the firing down during the phase just before the frit begins to melt. In this case it is around 1300-1400F.

Are You Ready for a Matte Version of this Recipe?

Yes, we have a very good matte version that can be tuned to fire with a surface very close to the classic dolomite magnesia mattes of cone 10 reduction (see links).

Conclusion

If you feel this was all too complicated, take heart. All of us are in over our heads, the ceramic process is exceptionally complex and none of us are really in control. So we need tools to better understand it. The oxide viewpoint provides a solid framework within which we can grow and learn together, even criticize each other. Yes this framework gives you the opportunity to explain how I am totally wrong about something in the above analysis. Then this base glaze would get even better. So let's at least start the new journey.

Related Information

The glaze dragon!

There are many mindsets that prevent us to getting control of our glazes. Many of them have nothing to do with the glazes themselves, the problem is with us, our culture as ceramists and potters.

Stains that work better in some glazes and not others

This demonstrates how the host glaze affects the color development of certain stains. Blue is stable in pretty well all glazes. But chrome tin pink (top row) is very particular that the glaze have the right chemistry (1214M is obviously best, it has the highest CaO and lowest ). The 6100 brown works much better in the N and O base glazes (they have higher ). Stain companies have guidance on chemistry particulars and you can view the chemistry of your recipe in your account at insight-live.com.

The main recipe window in Digitalfire Insight software

Insight installs on your Linux, Windows or Mac computer. It provides a very interactive way to comparing two recipes and their calculated formulas or analyses. As you make changes in the recipe you can see how it impacts the recipes. It is ideal for demonstrating concepts like unity, analysis,
formula, mole%, LOI, formula-to-batch conversion.

Links

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cone 6 5 transparent base glaze pottery ceramic

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All Articles A Low Cost Tester of Glaze Melt Fluidity A One-speed Lab or Studio Slurry Mixer A Textbook Cone 6 Matte Glaze With Problems Adjusting Glaze Expansion by Calculation to Solve Shivering Alberta Slip, 20 Years of Substitution for Albany Slip An Overview of Ceramic Stains Are You in Control of Your Production Process?

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Ceramic Stains: The Easy Way to Create All the Colors of the Rainbow on Your Pottery Find out everything you need to know about ceramic stains! Plus, get a new glaze recipe to try out with your favorite ceramic stains! John Britt

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Published Feb 16, 2022

Nowadays, ceramic artists are spoiled. It wasn't that long ago that getting the colors and surfaces you wanted took a lifetime of experimentation. But because of developments in modern stain technology, we have practically every color of the rainbow at our fingertips with commercial ceramic stains.

In this post, John Britt explains the ins and outs of ceramic stains and shares a recipe for you to experiment with. - Jennifer Poellot Harnetty, editor.

Ceramic stains are a mixture of ceramic oxides and coloring metal oxides that are melted in kilns, quenched, ground to specific mesh size (some are acid washed), and colored with organic dyes to simulate the fired color. Essentially they are fritted colorants. They are made and manufactured for several reasons: to provide a consistent and stable form of colorant that doesn’t dissolve in the glaze melt as easily as coloring metal oxides; to make colorants safer to use than raw metal oxides (commercial stains are less soluble in water); to allow repeatable and consistent results with minimal effort; and to allow you to fine tune your color selection to get the color you want at a reasonable cost. They can appear expensive, but time is money. Consider the countless hours of glaze testing that would be necessary without the consistency of a dependable commercial stain, then the prices are more reasonable.

Defining the Terms Surrounding Ceramic Stains

Frits: Ceramic materials that have been mixed, fused/melted/sintered together in a kiln, quenched, and ground to a specific size. They can be used as part of a glaze recipe (e.g. Ferro frit 3134) or added to coloring oxides, or ceramic stains to assist in melting.

Spinel: Mineral with alkaline oxide and amphoteric oxide. RO/R2O3. Gemstones are an example of natural spinels while in ceramics, these spinels are used to produce commercial colorants because they are chemically stable in molten glass. A purple can be created by combining cobalt and alumina oxide, CoAl203, into a cobalt aluminate stain.

Stains: 1) Coloring oxides suspended in water (a.k.a. an oxide wash). May also contain frit and/or kaolin (usually EPK). 2) Commercial ceramic colored powders that are used in glazes, clay bodies, and slips/engobes. Prepared coloring oxides that are fritted, reground, and colored with organic dyes to simulate fired color.

Properties and Characteristics

Historically, potters made glaze from feldspar, ash, and whatever iron-rich clays were available locally. This usually meant brown pots, or occasionally another earth-tone color. Then they began using metal oxides—like copper oxide, chrome oxide, manganese, iron oxides—and blending them with opacifiers to create colors. There is historic evidence that colored frits were used at least as early as 2600 BCE. Egyptian blue was a combination of silica, limestone, sodium, and copper oxides. This required a great deal of knowledge about glaze chemistry and firing to achieve the desired colors. And this knowledge was something that was in short supply, so potters basically accepted the glazes they stumbled upon and liked enough to build a body of work around.

Commercial stain companies provide a detailed list of what oxides are present in each stain (check out our directory to find ceramic stain suppliers!). The exact recipe is proprietary, but knowing what oxides are used in a given stain can give you great clues as to how a color is achieved or how to encourage or prevent particular effects. For example, there are several different black stains. One is Best Black while another choice is Cobalt-Free Black. If you are using a white glaze with a black-stained glaze next to it, you may notice that a blue line develops at the overlap. If you don’t want that line, you can look in the stain chart and choose the black stain without cobalt—the cause of the blue line.

This chart also tells the base glaze structure that is necessary for each stain to work. Before deciding on a color, it is advisable to look at the reference notes associated with that stain. Sometimes called the Base Glaze Guide, this information indicates the specific requirements to achieve each color. For example, the name is listed, followed by the oxides it contains, and finally a list of numbers such as 3, 5, and 9; each indicating information important to the mixing, firing, etc., to that stain: #3: Maximum firing limit 2300° F (1260°C), #5: Do not use zinc in glaze, and #9: Glaze must contain 6.7–8.4% CaO (12–15% CaCO3). Each manufacturer will have a full list of reference notes for their ceramic stains.

Each color is not guaranteed in all bases, and being aware of these reference notes will help you achieve greater success. Ceramic stains are not meant for all firing conditions and are generally designed for neutral or oxidation firing atmospheres (although some may work in reduction atmospheres). Because ceramic stains contain coloring metal oxides along with other ceramics materials like opacifiers, silica, and alumina, adding them to certain glaze bases can cause a glossy glaze surface to turn matte. Ceramic stains are generally added at 5–8% in a glaze and 15–25% in slips and clay bodies. At 8% most of the glazes are opaque and flat but if you add smaller amounts of stain (1–3%) it is possible to get transparent colors, including some very nice transparent celadon-colored glazes, when fired in an electric kiln or similar neutral atmosphere.

Encapsulated (Inclusion) Stains

Specialty stains, called encapsulated stains, allow potters to get colors that were once not possible with traditional ceramic stains. These stain types, also known as inclusion stains or inclusion pigments, are zirconium silicate with cadmium sulfoselenide crystals (Ca/Se). Dave Finkelnburg explained in his article, “Four Ways to Red” on pages 14–15 in the April 2011 issue of CM, “The discovery of the encapsulation process (the melting of the colorants into a zirconium silicate glass at high temperatures) has now made the many hues of yellow through red reliable at temperatures through cone 10 in both oxidation and reduction atmospheres.” The addition of 3% zirconium silicate will produce an even brighter color. These stains are refractory at higher temperatures, they do not melt much, if at all. As Tony Hansen writes on Digital Fire (www.digitalfire.com), “Encapsulated stains are not, as the name suggests and some misunderstand, a zircon capsule around an otherwise unstable compound. Rather they are manufactured by sintering to form a crystalline matrix (in a process called encapsulation).” Inclusion stains have specific firing temperatures and duration of firing protocols as well as warnings about not ball milling the stains (which will allow release of cadmium and/or selenium). If the fired glaze surface is damaged it can release the crystals.

Finkelnburg also states that cadmium stains can produce food-safe colors; however, under certain circumstances, it can be leached from the fired glaze. He adds that a sample of any cadmium-stain-tinted glaze used on potential food surfaces should be tested for leaching by a qualified laboratory.

Washes

Washes made with commercial ceramic stains can be used both over and under many glazes. Mason Color Works recommends mixing 85% stain and 15% Ferro frit 3124 as a starting point, but many potters us a 50% stain and 50% frit ratio with good success. When used under a glaze, cover with a transparent or semi-transparent glaze. When used over a glaze, be sure to have sufficient flux in the mix because if the stain or wash is too thick, it can turn into a crusty surface after the firing.

A very popular use of washes is on majolica-glazed work. Potters using majolica often mix 50% stain with 50% frit or Gerstley borate to brush designs on top of the white majolica-base glaze. If the ceramic stains are refractory, as listed by the manufacturer, increase the flux—use 1 part stain and 4 parts frit or Gerstley borate.

**First published in 2013.

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Ceramic Stains: Make Great Glaze Colors with Ceramic Stains

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Ceramic stains are a mixture of ceramic oxides and coloring metal oxides that are melted in kilns, quenched, ground to specific mesh size and colored with organic dyes to simulate the fired color. Joh

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Browse Topics

Pottery Making Techniques

Salt Firing and Soda Firing

In this section, ceramic artists will share the results of their experimentation with the salt and soda firing process. You’ll find everything from firing schedules to glaze recipes, to beautiful examples of salt and soda fired work.

Salt firing is a vapor-glazing process where salt (sodium chloride) is introduced into kiln firebox at high temperature. The salt vaporizes, and sodium vapor combines with silica in clay surface, forming extremely hard sodium-silicate glaze.

Soda firing has been touted as modern-day nontoxic replacement for salt firing, but has proven to be much more than that. Potters have discovered that soda firing has endless exciting aesthetic possibilities rather than just being a more environmentally friendly! In the soda firing process, soda ash (sodium carbonate) in water solution, instead of salt, is sprayed into kiln at maturing temperature, and sodium vapor combines with silica in clay to form sodium-silicate glaze. In these archives, salt and soda firing artists share practical technical information, salt and soda glaze recipes, atmospheric slip recipes, and salt and soda glazing and firing techniques. In these archives, salt and soda firing artists share practical technical information, salt and soda glaze recipes, atmospheric slip recipes, and salt and soda glazing and firing techniques.

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Soda firing has been touted as modern-day nontoxic replacement for salt firing, but has proven to be much more than that. Potters have discovered that soda firing has endless exciting aesthetic possibilities rather than just being a more environmentally friendly!

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GLAZE RECIPES

Glaze recipes are typically expressed by listing each raw material and its % by weight. The percentages add up to 100 Usually colorants and sometimes other additives (such as bentonite for suspension) are not included in the 100%, they are added on afterward.

EXAMPLE: CONE 6 CLEAR BASE GLAZE

To mix this glaze, you take the total number of grams of dry material you are making, multiply by the % to get the grams of each material to add.

EXAMPLE: TO MAKE 1000G OF GLAZE

Wallastonite = 10/100*1000=100 grams

FRIT 3134=30/100*1000=300 grams

Kaolin = 25/100*1000=250 grams

Flint = 15/100*1000 = 150 grams

F-4 Feldspar = 20/100*1000 = 200 grams

To double check, add up all the grams and make sure they equal 1000.

Then add 4/100*1000 = 40 grams cobalt oxide

This is as far as many people go. They make the glaze, test it, and often are unhappy with the results. So let's go further and understand why.

GLACE COMPOSITION

Every glaze is made of the following 3 materials:

Silica - Creates glass. Examples: quartz, flint, pure silica

Alumina - Stiffens the glaze so it doesn't slide off the clay. Examples: clay (kaolin, ball clay, or fire clay), alumina hydrate

Flux - Causes the glaze to melt at a low enough temperature to be used in ceramics. Examples: feldspar, whiting

Plus a glaze may include one or more additives:

Opacifiers - to make the glaze opaque instead of transparent. Examples: tin oxide, zirconium or Zircopax, titanium, zinc

Suspenders - to keep the glaze in suspension instead of settling out. Examples: bentonite

Colorants - to provide various colors. Examples: cobalt oxide, copper oxide

To make a glaze, we need to find sources of each of the above which are convenient to use, in a form that does not dissolve in water. As we saw in the last tip (#34), glaze materials can be broken down into their chemical compositions, and from there we can see what the effect of each material will be.

To provide silica in the glaze, we need a material than contains: SiO2=Silicon Dioxide, comes from flint, quartz and pure silica

To provide alumina in the glaze, we need a material that contains: Al2O3=Aluminum Oxide, comes from feldspar, cryolite, clay

FLUXES

Silica and alumina would create a glaze if fired hot enough. However, ceramic kilns are do not reach the temperatures required. Therefore, we need to add fluxes, which lower the melting point.

To provide flux in the glaze, we need a material that contains one or more of the following:

Li2O=Lithium Oxide, comes from Lithium carbonate, Petalite, Spudomene

K2O=Potassium Oxide; comes from Potash Feldspar, frit

CaO=Calcium Oxide, comes from whiting, limestone, wollastonite (also provides SiO2), wood ash, bone ash, dolomite (also provides MgO)

MgO=Magnesium Oxide, comes from magnesium carbonate, dolomite (also provides CaO), talc

ZnO=Zinc Oxide, comes from zinc oxide

SrO=Strontium Oxide, comes from strontium carbonate

BaO=Barium Oxide, comes from barium carbonate

PbO=Lead Oxide (not used much due to toxicity)

Na2O=Sodium Oxide, comes from feldspar, FRIT, cryolite, nepheline syenite

TiO2=Titanium Dioxide, comes from pure titania, rutile

ZrO2=Zirconium Dioxide, comes from zirconium dioxide, zircopax, zirconium silicate

SnO2=Tin Oxide, comes from stannic oxide (SnO2 white), stannous oxide (SnO black)

B2O3=Boric Acid or Boron, comes from Colmanite, Gerstley Borate, CadyCal. Effective for lowering the melting point of a glaze.

Now don't panic! This isn't chemistry class, and you don't have to memorize this list! But if you've worked with glaze recipes at all, you probably recognize many of these terms, and can start to understand what they are used for.

You can take any glaze recipe, and break each ingredient down into it's chemical composition as shown last week. An easy way to do this is by looking up the material in the DigitalFire database. http://www.ceramicsearch.com/material/

Once you have the chemical composition of the ingredient, you can see what it contributes to the glaze. For example, is it primarily contributing silica, alumina, or a flux? Often a single ingredient contributes a combination of these. For example, Feldspar is primarily a combination of alumina and silica. And so is clay.

Glazes need a balance of the 3 main ingredients: Silica, Alumina and Flux.

Too much flux causes a glaze to run, and tends to create variable texture on the surface. The texture may vary from shiny, where the glass is balanced, to matte where the excessive flux oxides may form visible, possibly lumpy, crystals.

Too much silica will create a stiff, white and densely opaque glass with an uneven surface. It will be glossy in spots, but the suspended silica can form crystals producing harsh dry surfaces. Too much silica will also inhibit the melting of a glaze, and the resulting surface will be roughly textured like sandpaper.

Too much alumina causes a glaze to stiffen and tend towards opacity, again with a textured surface where it is dry in spots. Glazes will often have pinhole defects. Too much alumina can inhibit the melting of the glaze to the extent that a poor quality matte glaze results, one that looks matte but is prone to discoloration.

SO HOW DOES THIS HELP YOU?

By understanding what different materials do, you can adjust a glaze recipe to change its characteristics or fix its problems. For example, you can make a transparent glaze into a matt glaze. You can stop crawling, pinholing, or crazing. You can lower the melting temperature of a glaze. You can make a substitution if you run out of an ingredient. This ability completely changes the way you work with glazes.

UNITY FORMULA AND GLAZE CALCULATION PROGRAMS

You may have heard of something called a unity formula, or Seger formula. This is a way of expressing a glaze by the ratios of its oxides rather than % of raw materials. It is one of the primary methods used in analyzing glazes. I'm going to skip the detailed math. But the concept is that using information about each raw material, you create a ratio of the amount of flux to the amount of silica and alumina. These ratios can then be compared to ones which have been determined to work in a certain way at a specific temperature.

These calculations are very detailed and take a long time to do by hand. And because there are many factors that all interact, it would take a long time to learn each material and the effect it has on a glaze. So potters have created a variety of computer programs that simplify the analysis and formulation of glazes.

You can learn more by taking the self paced on-line tutorial called Glaze Teach. http://www.matrix2000.co.nz/GlazeTeach/Index.htm The writers of this tutorial offer a glaze calculation software program called Matrix.

Or visit DigitalFire http://www.digitalfire.com, a website that explains glaze chemistry and sells a software program called Insight to help automate this glaze analysis process.

So, if this whole thing looks interesting to you, you will probably want to explore the world of glaze chemistry more. On the other hand, if it makes your eyes glaze over (no pun intended), you probably should stick to commercial glazes or trial and error. Happy glazing!

(note, the numbers in the above chemical formulas would properly be expressed as subscripts)

Browse our huge selection ofglazes.

copyright 2001, www.bigceramicstore.com

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UNDERSTANDING GLAZES GLAZE RECIPES Glaze recipes are typically expressed by listing each raw material and its % by weight. The percentages add up to 100 Usually colorants and sometimes other additives (such as bentonite for suspension) are not included in the 100%, they are added on afterward.

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BigCeramicStore.com is the leading retailer of pottery supplies and equipment in the United States.  Since 1999, we've been committed to supporting creative artists. Whether you're just starting out or are an expert potter, we have the right products for you.  And if you need help deciding what to get, fear not.  We have expert potters on staff to help you along the way.  We're here for you!  We ship products from Sparks, NV and West Lebanon, NH, so you can count on getting your supplies fast.

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Welcome to our ceramic “how-to’s” page! We have over 100 tips, tricks and tutorials on ceramics and glass. Whether you’re a beginner just getting started with ceramics or an expert with warm glass looking to expand your skill set, this is the place for tutorials, instruction and ideas to help you al…

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BigCeramicStore.com is the leading retailer of pottery supplies and equipment in the United States.  Since 1999, we've been committed to supporting creative artists. Whether you're just starting out or are an expert potter, we have the right products for you.  And if you need help deciding what to get, fear not.  We have expert potters on staff to help you along the way.  We're here for you!  We ship products from Sparks, NV and West Lebanon, NH, so you can count on getting your supplies fast.

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I imagine you found this article because you're already producing pottery and are interested in making your own pottery glazes. You're in the right place!

There are many books on glaze making which cover this topic in much more depth. To be honest I haven't read many of them - and I do like reading books.

I hope this doesn't give the impression I just chuck a load of ingredients in a bucket and hope for the best. My glazes are used for functional pottery and my children use them to eat from. I want to make sure they are done right.

I have mainly used resources from the internet to help with glaze development - I'll share those with you later. But first...

Why make your own glazes?

Perhaps if the first commercially made glazes I bought were great, I might not have started trying to make my own. The glazes I bought first were a very plain black, a boring white and a horrific green so I started researching about glaze making almost immediately.

I did choose some rubbish glazes to be fair. There are some very beautiful ready made glazes if you choose the right ones. They can be bought in powder form to just add water, or as a liquid glaze. If you have never used a glaze before it's worth buying a ready made one. It will give you experience in mixing, sieving and applying the glaze. Commercial glazes are often quite forgiving if applied a little too thin or thick, or if they are fired to not quite the right temperature.

As you can buy a perfectly good ready made glaze, the biggest reasons for making your own are:

1. You have complete control. You may decide you want the glaze to be less glossy, more matt, a bit more blue, have speckles, melt at a lower temp or any other glaze variable. All these things can be altered by adjusting your recipe

2. Cost. It's simply cheaper to make your own. Very roughly I'd say it's half as expensive to make your own. That's a lot of money after a few kiln loads!

If I'm selling it to you so far you might want to jump straight into buying some powder and mixing stuff up. But whoa there a minute, let's think about a bit of glaze theory first.

What are the main components of glaze?

If you've read any other articles on glaze making you may have read about the three main glaze components:

Glass-Formers

Fluxes

Stabilisers

It's important to understand that certain glaze ingredients can contribute to more than one of these components. For example, the glaze ingredient Wollastonite is 52% Silica (glass-former) and 48% Calcium (flux).

But to start with let's look at the components.

Glass-formers mostly come from silica - it's the part of the glaze which actually forms the glass. There are a few technical variations but it's basically just sand.

If we were to make a glaze using only silica, the melting temperature would be around 1700 Centigrade.

To avoid having to fire at such high temperature a flux is used in glazes. Just think of flux as a little gremlin that helps make glazes melt. Lower temperature glazes need more flux.

If glazes had no Stabilisers they would melt so well they would run off the pots and all over the kiln shelf into a big puddle. The Stabilisers (Alumina and Boron) helps stiffen the glaze so it can melt to a nice glass but not run off the pot.

Developing a glaze recipe

The first glazes I made were based on some excellent documentation from the Digital Fire website. It does such a great job at describing many aspects of glazes and I suggest you read all the articles here - especially the food safe, toxicity & safety ones. At the time I was firing to cone 6 in an electric kiln, and the G1212W recipe made an ideal base.

I would recommend using a recipe like this as a base glaze for beginners. Various colouring oxides can be added to provide colour, and the quartz to clay content can be adjusted to determine how matt or glossy the glaze is.

If you are determined to create your own glaze from scratch you will need to decide on the following before creating a recipe:

1. What cone / temperature is the glaze going to be fired to. This will be determined by the clay you are using, and perhaps limited by the maximum temperature of your kiln.

2. Are you firing in oxidation or reduction atmospheres

3. Are you looking for a matt or glossy surface to the glaze

4. What colour are you aiming for

5. Is the glaze to be used for food or drinks

I'm starting to feel a little overwhelmed trying to explain all this. There are so many things that counteract with each other in a glaze recipe. Perhaps it would be a good time to introduce the limit formula. I guess the limit formulas were devised to stop potters heads boggling when devising glazes.

Each ingredient in a glaze contributes a certain amount of different oxides into the glaze. If the oxide levels in your glaze is within the limit formula it should be a fairly solid glaze. See the following section about how to calculate oxide levels in glaze recipes.

If you are intending your glaze to be used on a food surface it should be within the limit formulas. I make sure all my glazes are withing limits - there's no way of knowing if someone decides to drink champagne from a flower vase. The limit formula doesn't guarantee safety, but it's a good starting point.

The limit formulas can be used as a starting point for finding how much flux is needed for each cone range. The amount of gloss can be controlled by adjusting the silica to alumina ratio within the limits.

Colouring oxides can be fickle, depending on the kiln atmosphere, base glaze ingredients the firing schedule of a kiln and many other factors. Much testing is needed to achieve the desired result.

Software and websites for calculating glaze recipes

While you could calculate glaze recipes with paper and pen, there are a few great websites that make glaze development a lot easier.

With each of these websites you enter the glaze ingredients, and a percentage amount for each one. Glazes are normally written with the main ingredients adding up to 100, and colouring ingredients as additions.

The first website I ever used was glaze simulator. This is really nice and easy to use once you get the hang of it. You can store recipes in the browser but they will disappear if you delete your cookies at any point. It has the advantage over the others that it shows a suggested cone melting range for the glaze. Some of the oxide calculations are quite different to the other websites so I'm not sure of it's ingredient accuracy.

I then used the insight live website for while. I got a free group membership through the cone6pots.ning website. Individuals can pay for membership on their own. I really appreciate the work that has gone into this program and the ingredients database and other information is amazing. The glaze calculator itself is a bit clunky to use, although I'm sure it's very accurate.

The most recent website I've used is glazy.org. This site is a great community with many recipes to browse through. It's easy to use and I really like the way you can search glazes using a colour picker. The charts that show similar glazes to the one selected are also really cool. I haven't fully explored all the features, but I think I'll be mostly using this site in future.

Buying glaze ingredients

One mistake I made when first buying glaze ingredients was buying the same amount of each type. In my glazes I use a lot of quartz, china clay and soda feldspar so I now buy these in larger quantities.

Most of the main glaze ingredients for base glazes are fairly cheap so it's not such a worry. The most expensive base ingredient are usually the frits. These can be around 5 times the price of something like clay or quartz. They are also used in much smaller quantities on glazes, so that should be reflected in your ordering

Some of the colouring oxides can get very expensive. I buy things like cobalt  in very small sizes. The most a glaze is likely to use is around 1% cobalt. It's a good idea to work out your recipes and calculate the ingredients needed for a 5 kg batch to fill your glaze bucket. Doing this you can avoid overspending on ingredients that will sit in a packet for months.

Equipment needed for making glazes

Luckily you don't need much equipment at all to start making your own glaze. I use the following basic equipment for glazing.

Round buckets with lids. I use mostly 5 litre to 10 litre containers for glaze. Any smaller and you wont be able to dip things in there.

Sieve - This needs to be a mesh size of 80 or finer. They are available from ceramics suppliers.

Whisk - any old kitchen whisk for stirring up the glaze

Respirator with p100 rated filter - search amazon, they are around £30 with filters. The cheap dust masks from DIY stores are not suitable for the fine particle sizes of glaze ingredients.

Digital scales - I just use cheap kitchen scales. They are not very accurate for test weights but I live with it.

Large paint brush - like for painting the walls of your house.

Mixing your first pottery glaze

Finally! So by this stage you should have a glaze recipe, your ingredients and the equipment listed above. Good job getting this far...

Your glaze recipe will probably add up to around 100 percent, you now need to decide how much glaze to make. Usually when I'm testing a glaze for the first time I'll just mix one part, i.e around 100g of ingredients with the same weight of water. This will just make enough to dip a small test tile.

If you want to make enough glaze to dip a mug you'll probably need around 2 kg of dry ingredients mixed with around 2 litres of water. To get the weight of each ingredient in this case multiply the recipe amounts by 20 as shown below. You could use an excel spread sheet to calculate your batches if you're as geeky as me.

Recipe:

20 Wollastonite

10 Calcium Borate Frit

20 China Clay

15 Quartz

35 Soda Feldspar

2kg Batch:

400g Wollastonite

200g Calcium Borate Frit

400g China Clay

300g Quartz

700g Soda Feldspar

1. Put your respirator on

2. Fill a bucket with your starting amount of water ( 2 litres in this case).

3. Set a container on your scales and zero them.

4. Then add your first ingredient up to the specified weight. Try and create as little dusk as possible by carefully scooping ingredients out of their package rather than pouring them.

5. Carefully pour the weight ingredient into the bucket with water in.

6. Repeat for each ingredient and cross them off your list as you add to the bucket.

7. Once all ingredients are in the water carefully whisk them together to avoid too much dust creation.

8. Add more water if needed until the glaze is somewhere between milk and single cream thickness.

9. Get another clean bucket and put your sieve on top.

10. Begin pouring your mixed glaze into the sieve. Do this in stages and use the paint brush to mix around the glaze in the sieve. This bristles will help the glaze move through the sieve.

11. Clean the area and tools before removing your respirator.

12. Leave the glaze to sit for 24 hours before using to ensure all the particles have soaked into the water properly.

13. Mix glaze with whisk thoroughly before and during use

Making your own pottery glaze conclusions

At the start I mentioned that it's important to not confuse the components of a glaze with the glaze ingredients. I took the example glaze recipe from above and entered the ingredients and quantities in glazy.org.

After saving it as a new glaze I was able to see the UMF (Unity Molecular Formula). This shows that the example glaze ingredients have the following components:

Glass-formers : 3.51 Silica

Stabilisers : 0.54 Alumina , 0.25 Boron

Fluxes : 0.23 Sodium, 0.76 Calcium

There are loads of other cool ratios and charts to see. I highly recommend having a look a Glazy -  it's such a great free resource.

That's about as far as I want to take this article. Whether or not you made a good glaze is in the eye of the beholder. There are a number of tests you can do to check the safety of a glaze - see digital fire articles linked to before.

Hopefully this post was useful for you. I'm keen to make it more useful, so if there are things I didn't explain well or need expanding on please leave a comment. I will try to answer any questions you have.

If you make some killer glazes and are at the point of selling your work you may be interested in my guide to selling pottery online.

If you are just getting started in pottery you may also be interested in my beginners guide to tools and equipment.

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A Beginners Guide To Making Your Own Pottery Glaze - Step by Step

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I imagine you found this article because you’re already producing pottery and are interested in making your own pottery glazes. You’re in the right place!

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Ceramics: Art + Perception - An international bi-annual full color print publication posted to your door.

Clay Gulgong - Australia's great international ceramics festival. Morning View - A world-renowned ceramics studio and artist residency in Gulgong, Australia.

Morning View Residency, our historical property in Gulgong. Artists are invited to apply to live and work at the property.

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Ceramics: Art + Perception - An international bi-annual full color print publication posted to your door. Clay Gulgong - Australia's great international ceramics festival. Morning View - A world-renowned ceramics studio and artist residency in Gulgong, Australia. Morning View Residency, our historical property in Gulgong.

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Centering large amounts of clay!

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Ceramics Periodic Table

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GlazeTeach - a basic course in glaze technology.

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Matrix Glaze Teach

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GlazeTeach - a basic course in glaze technology.

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GlazeTeach is a course in basic glaze technology for beginners published by Matrix Glaze Calculation Software.

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John Parker Ceramic Artist and Designer - Auckland New Zealand

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John Parker - Technical pages

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John Parker Ceramic Artist and Designer - Auckland New Zealand

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John Parker Ceramic Artist and Designer - Auckland New Zealand

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Technical Articles

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An integrated materials-centric, basic concepts database for traditional ceramics

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Material Hazards

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Hazards in the making and use of traditional ceramics.

Alumina Toxicology | Ammonia and Latex Toxicity | Antimony Oxide | Arsenic Oxide | Asbestos: A Difficult-to-Repace Material | Ball Clay | BARIUM and COMPOUNDS / Toxicology | Barium Carbonate | Bentonite Toxicity | Beryllium Monoxide Toxicology | Bismuth Trioxide Toxicology | Boron Compounds and Their Toxicity | Brown Stain | Cadmium Toxicity | Calcium Carbonate Toxicology | Carbon Monoxide Toxicity | Cesium Toxicology | Chromium Compounds Toxicology | Cobalt Oxide and Carbonate | Cobalt Toxicology | Copper Compounds Toxicology | Copper Oxide and Carbonate | Cristobalite Toxicity | Cryolite and Ceramics | Dealing With Dust in Ceramics | Diatomaceous Earth Toxicology | Dioxins in Clays | Epsom Salts | Eye Injuries Due to Radiation | Feldspar | Fighting Micro-Organisms in Ceramics | Fluorine Gas | Gallium Oxide Toxicology | Hafnium Oxide Toxicty | Hydrofluoric Acid Toxicity | Iron oxide and Hematite | Kaolin Toxicity | Lead Chromate | Lead in Ceramic Glazes: What Did We Learn? | Lead in Frits: The Hazards | Lead Toxicology | Lithium Carbonate Toxicity | Lithium Toxicology | Man-Made Vitreous Fibers (MMVF) Toxicology | Man-Made Vitreous Fibers Safety Update | Manganese and Parkinsons by Jane Watkins | Manganese in Clay Bodies | Manganese Inorganic Compounds Toxicology | Manganese Toxicity by Elke Blodgett | Manganese: Creativity and Illness by Dierdre O'Reilly | Molybdenum Compounds Toxicology | Nickel Compounds Toxicity | Niobium Oxide Toxicity | Occupational Dermatoses | Overview of Material Safety by Gavin Stairs | Paraffin Toxicology | Perlite Toxicity | Plant Ash Toxicity | Potassium Carbonate Toxicity | Pregnancy and Ceramics | Propane Toxicology | Quartz Toxicity | Quartz Toxicity on Clayart | Rare Earth Compounds Toxicity | Rubidium and Cesium Toxicology | Rutile Toxicology | Silicosis and Screening | Silver Compounds Toxicology | Sodium Azide Toxicology | Sodium Carbonate Toxicology | Sodium Silicate Powder Toxicology | Stannous Chloride Toxicity | Strontium Carbonate Toxicity Note | Sulfur Dioxide Toxicity | Talc Hazards Overview | Talc Toxicology | Thallium Oxide Toxicology | The Use of Barium in Clay Bodies | Thorium Dioxide Toxicity | Tin Inorganic Compounds | Titanium Dioxide Toxicology | Toxicological Assessment of Zeolites | Tungsten Compounds Toxicology | Understanding Acronyms on MSDS's | Uranium and Ceramics | Vanadium and Compounds Toxicology | Vermiculite | Zinc Compounds Toxicology | Zirconium Compounds Toxicity | Zirconium Encapsulated Stains Toxicity

A wide range of materials are used in ceramics. Many of them are harmless, they can be breathed or eaten will little effect. Hundreds of tons of clays are sold each year for the specific purpose of eating them! And many more for cosmetic and medicinal uses. Most ceramic materials are inert, insoluble and among the most stable of materials. That means that it is not dangerous to, once in a while, touch or handle the vast majority of materials. However, if there is constant exposure, then long term effects need to be considered. Notwithstanding this, there some materials do have specific acute or short-term exposure hazards (by ingestion or inhalation).

Material hazards are most commonly related to the dust. But there is a need to be sensible about it. One cigarette, for example, does not kill. Nor do 100. But 100,000 can. Likewise, there may be some asbestos fibres in talc or vermiculite, but you will not be harmed by sweeping up a little of either. You will be harmed if exposed to the dust daily for years and take no precautions. Consider frits to illustrate the need for common sense: There are hundreds available. They are ground glass powders, that means each particle is a glass shard, potentially with razor sharp angular edges! It it not easy to find hazards information on frits (likely because there are so many types and each pulverizes to a different particle shape). Yet simple logic tells us to be careful about breathing the dust. And, to illustrate the need for perspective, consider silicosis: It is a much more serious health issue than asbestosis. Yet pretty well all dust in nature contains some quartz. Even gardening, farming or just walking in dry areas expose one to quartz dust. This is because quartz makes up 10% of the planet. So minimizing exposure over the years is the common sense approach.

Some materials produce harmful fumes at certain temperatures during firing. Bodies or glazes with high percentages of manganese dioxide (and other metal oxide raw materials), for example, will fume and should be considered hazardous. The obvious precaution is to install a vent on your kiln.

Some materials are poison or toxic if eaten. Barium carbonate or lithium carbonate are examples. But this is not common.

Links

Flow diagram of a pottery operation

Each stage presents potential health hazards. Photo courtesy of American Conference of Governmental Industrial Hygienists.

By Tony Hansen

https://digitalfire.com, All Rights Reserved
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Hazards in the making and use of traditional ceramics.

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Specific Gravity

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Written By Jake Corboy

Measuring the specific gravity of your glaze is very important. It allows you to mix different batches of the same glaze consistently. It helps you decide if you should add more water to a glaze to thin it down, or deflocculate it with a dispersal instead. It also helps when water has evaporated out of a glaze that has been sitting around for awhile. This way, you're able to bring it back to its original consistency. Basically, measuring specific gravity is telling you how much water is in your glaze.

There are several ways to measure the Specific Gravity of a glaze. I prefer using a 50ml plastic plunger syringe, because it is fairly quick, accurate and easy to measure with and clean.

Here is how to go about measuring the specific gravity of a glaze with a 50ml plastic syringe:

1) Weigh the plastic syringe and write it down. The syringe should be clean and completely dry when doing this.

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Measuring the specific gravity of your glaze is very important. It allows you to mix different batches of the same glaze consistently. It helps you decide if you should add more water to a glaze to thin it down, or deflocculate it with a dispersal instead.

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How to Make Casting Slip from Your Clay Body - A Simple Technique

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How to - Casting Slip from your clay

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How to Make Casting Slip from Your Clay Body - A Simple Technique

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In this post, Paul Andrew Wandless shows you how to make casting slip from a clay body normally used for throwing or handbuilding. How to make casting slip from a regular body is an important skill fo

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How to - Prepare wood ash for glazes

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How to Fix a Hard-Panned Glaze with Epsom Salts - Sue McLeod Ceramics

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How to - Fix hard panned glaze with ES

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Why Do Glazes Hard-Pan?

Have you ever had a glaze settle into a rock hard layer on the bottom of your glaze bucket? It's impossible to mix and even if you do get it mixed, it just settles out again.

This annoying phenomenon is called "hard-panning" and it often happens to glazes that don't have enough clay in them to keep the glaze in suspension.

Clay is a very light material and is the main suspending agent in our glaze recipes.

Our glazes are made up of rocks that have been ground up into a fine powder. Naturally, they would just sink (like rocks) to the bottom of the glaze bucket.

Next time you make 10 kg of glaze, think about how hard it would be to stir a 10 kg bucket of rocks with a spatula.

But when we add clay to our glazes (in the form of kaolin, ball clay or bentonite), the clay helps to keep the heavy particles in suspension, floating around the bucket and very easy to stir with a spatula.

For this reason, it's ideal to have at least 10% clay (kaolin or ball clay) in any glaze recipe.

For glaze recipes that contain little to no clay, 1-2% bentonite can be added with little to no effect on the fired results.

Bentonite is also clay, but it's much finer and has a smaller particle size and higher surface area than kaolin or ball clay. Because of this, it's a much more powerful suspending agent.

1% bentonite has approximately the equivalent suspending power as 5% EPK.

So if your glaze recipe has no other clay in it, I would add 2% bentonite.

If your glaze has some clay but less than 10%, I would add 1% bentonite.

This should be enough to keep your glaze suspended and prevent hard-panning.

If you're mixing a new glaze with little to no clay in it, you can add the bentonite to your recipe to start out with. It's always better to prevent hard-panning than to have to fix it later.

If your glaze is already mixed and hard-panning, update your recipe now by adding 1-2% bentonite to it so you'll remember to include it next time you mix a new batch.

If you know the approximate dry weight of your already mixed glaze, you can still add bentonite after the fact. Just make an educated guess of the dry weight based on the last batch size you mixed and how much you've used since then. It doesn't have to be exact. Around 1-2% of the dry weight will be fine.

Before you start adding bentonite to your mixed glaze, you may want to read my blog post How to Add Bentonite to a Wet Glaze to learn about the challenges of adding bentonite to a wet glaze and how to get around them.

My Glaze Has Clay in it and it's Still Hard-Panning

Ok, so we've established that glazes need at least 10% clay in them to stay suspended and if they don't have any clay, we can add 1-2% bentonite.

But... depending on your glaze's composition, it may contain some ingredients that counteract the suspending properties of the clay.

This means your glaze could have over 10% clay in it and still have trouble staying suspended. This usually happens in glazes that contain some form of soluble sodium.

A lot of glazes contain sodium, which is one of our primary fluxes that get the glaze melting in the kiln. When the sodium remains as a solid particle suspended in the water, it has no effect on the glaze's properties in the bucket.

But if some of that sodium dissolves into the water, the glaze can become naturallyDEFLOCCULATED.

Clay particles have positive and negatively charged sides and edges. They attract each other like magnets. This attraction is what helps the clay particles keep the rest of the glaze suspended.

But when positively charged sodium ions bond with clay particles (deflocculating them), they go from having positive AND negatively charged sides to having ONLY positively charged sides.

Since two positives repel each other rather than attract each other, their suspending properties are gone.

So to sum up deflocculation, it's when sodium ions are added to a glaze, whether intentionally or unintentionally, and they attach to the clay particles, turning their negatively charged sides positive so they repel each other.
All sides of deflocculated clay particles are positive so they repel each other.
Deflocculated glazes often have a thick layer of water on top before mixing and settle fast after mixing. They dry almost instantly after dipping the bisque.

In order to fix a naturally deflocculated glaze like this, we can add a FLOCCULANT and get the clay particles attracting each other again, which will help keep all the other particles suspended in the bucket.

Fix Your Hard-Panned Glaze with Epsom Salts

The two main reasons why your glaze is hard-panning:

1. There's not enough clay to keep the glaze suspended

2. Your glaze is naturally deflocculated

Always deal with the clay issue #1 first, if applicable, then move on to #2.

Flocculation and deflocculation can only effect clay particles. So if your glaze doesn't have any clay particles, it's not naturally deflocculated and flocculating it won't fix anything.

A glaze needs clay particles for flocculants and deflocculants to have any effect. Even a glaze with only 1% bentonite and no other clay can be flocculated/deflocculated. The key is, it must have clay particles.

If your glaze has clay in it then you can fix hard-panning by flocculating.

My favourite flocculant is a saturated Epsom salt solution. This blog post explains how to make a saturated Epsom salt solution and it goes into more detail about how flocculation works.

The video below shows a hard-panned glaze that contains 90% Frit 3110 and 10% EPK. Frit 3110 is one of those materials that contains soluble sodium.

So even though this glaze has 10% clay in it, it is naturally deflocculated and hard-panning.

In the video, I add saturated Epsom salt solution a few drops at a time until the glaze is flocculated and stays in suspension.

How Much Epsom Salts Solution to Add?

The glaze in the video contains 500g of dry materials and it took about 75 drops of Epsom salts to get it flocculated.

In my experience, that's a lot of Epsom salts for such a small amount of glaze. This is likely due to the high percentage of frit (a heavy material) and the comparatively low percentage of clay.

Every glaze composition is going to react differently to a flocculant. Some glazes of that size will only take a few drops to become flocculated. The more clay in the recipe, the easier it'll be to flocculate it.

Always start with a smaller amount than you think you need and work your way up.

Here's my general guideline for how much Epsom salt solution to add at a time, based on dry weight:

Up to 1000g - a drop or two at a time

1000g - 5000g - a teaspoon at a time

Over 5000g - a tablespoon at a time

Start with that and mix well with a high-speed mixer after every addition. I recommend an immersion blender or drill with paint mixer attachment.

If the amount you're adding is having zero effect, you can increase the amount.

Keep adding Epsom salts and high-speed mixing until you notice the glaze noticeably thicken. Then stop.

A flocculated glaze will stick to your finger, rather than run off, back into the bucket.

And a flocculated glaze will come to an abrupt stop soon after the mixing stops. If you stop mixing and the glaze keeps swirling around and around the bucket, it's probably not flocculated yet.

Extreme Cases of Hard-Panning

In the video above, I was able to get the glaze somewhat moving at first by using my fingers to scrape the particles off the bottom. This isn't always a possibility.

Sometimes your glaze will be so hard-panned that you can't get it to move at all. In this case, I would pour the water off the top of the glaze into a bucket. Save this bucket of water to add back into the glaze later.

Take the remaining hard layer of glaze and add some Epsom salt solution directly to it.

Either use your hands (wear gloves if glaze materials are a concern) or a tool to work the Epsom salts into the glaze layer. A metal spoon or large loop trimming tool works well to cut through the glaze.

It may take some elbow grease to get it going but eventually, the glaze layer will soften and start moving. Then you can add the water you removed back in and proceed to use your high-speed mixer.

Here's a quick video of me doing this. I already poured the water off the top and I'm adding Epsom salts to the hard-panned sludge. Once I get it moving, I add the glaze water back in and high-speed mix - voila!
Forgive the video quality, diminished by YouTube. (Video has no sound)
I hope this article gave you some insight to not only to fix your hard-panned glaze but to assess its cause so you can prevent it from happening in the future.

Do you have other strategies for hard-panned glazes? I'd love to hear them in the comments below.

If this post helped or inspired you, please share it with someone who might need to read it.

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How to Fix a Hard-Panned Glaze with Epsom Salts - Sue McLeod Ceramics

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Have you ever had a glaze settle into a rock hard layer on the bottom of your glaze bucket? It's impossible to mix and even if you do get it mixed, it just settles out again. This annoying phenomenon is called "hard-panning" and it often happens to glazes that don't have enough...

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How to Make a Saturated Epsom Salt Solution to Flocculate your Glazes - Sue McLeod Ceramics

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How to - saturated solution of Epsom Salts

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Flocculate... What Does That Even Mean?

You may have heard this term "flocculate" in reference to glazes and thought it was a funny word but you've never really known what it means.

Or you may have been told what it means several times and still don't really understand it.

Or, maybe you understand what it means but you always mix up "flocculate" and "deflocculate" because you can't remember which is which.

This sums up my own progression of understanding the word flocculate. I don't know why but it took me so long to really get it. Nobody ever explained to me in a way that solidified it in my brain.

I made a point to read every article and excerpt I could find about it until I was finally like "Ohhh, now it makes sense!"

I could write pages on flocculation and deflocculation now. It's a pretty complex subject when you get into the science, details and nuances of it but the basic principles are straight forward.
Flocculation affects how the clay particles in a glaze recipe interact with each other.
This is a very important distinction. Only the clay particles in a glaze are affected by flocculation. So your glaze recipe must first have clay in it (bentonite, kaolin or ball clay) for flocculation to work.

When a glaze is flocculated, the clay particles become attracted to each other and stick together instead of flowing freely past one another.
Here's how it works:
Clay particles are flat and thin, like tiny playing cards. They have flat "faces" and thin "edges". The edges and faces of a clay particle have a charge, positive or negative like magnets.

Positive attracts negative, but two positives or two negatives will repel each other.

The faces of a clay particle are negatively charged. The edges can be both negative and positive.

When you add Epsom Salts (magnesium sulphate) to flocculate a glaze, you're introducing positive magnesium ions to the glaze. These positive ions attach themselves to the edges of the clay particles so now the edges are all positive.

Since the faces have a negative charge and the edges have a positive charge, the clay particles all start attracting each other and sticking together, edge to face, face to edge.
Positive edges of clay particles are attracted and stick to negative faces.
This forms an open, house-of-cards-like network of clay particles throughout the glaze bucket. The clay particles are bonded together, but there are lots of open spaces in between them.

This open network of clay particles does a few key things.

1. It increases the viscosity of the glaze (making the glaze thicker)

2. It helps to keep all the other particles suspended in the bucket

3. It increases the time it takes for a glaze to dry after applying, promoting a smoother application

So, if you're wondering whether your glaze needs to be flocculated with Epsom Salts, consider these three issues.

1. Are you trying to thicken your glaze?

2. Does your glaze need help staying suspended in the bucket? Is your glaze hard-panning?

3. Is your glaze drying too fast, causing an uneven application layer?

If your answer to any of these questions is YES, then you may need to flocculate your glaze.

So to sum up what flocculation means, a flocculated glaze has clay particles that stick together, rather than move freely past one another.

A popular way to remember this is the clay particles "flock" together, like sheep flock together. Flock-ulate.

We didn't talk about deflocculating in this post, but another mnemonic device I use to remember the difference between flocculants and deflocculants is that Darvan is a Deflocculant and a Dispersant - all starting with D.

Whatever it takes to figure this stuff out, right?

Read This Before Flocculating

Flocculating should always come AFTER measuring specific gravity. Measuring specific gravity is a way to calculate whether your glaze has the ideal amount of water for your application method.

You must get the water content right before determining whether your glaze needs to be flocculated.

If your glaze is too thin or won't stay suspended because it has too much water, then flocculating isn't going to help. In some cases, it will make your glaze application worse.

The only way to know whether your glaze has the right amount of water is by measuring specific gravity. It's a quick and easy process that will improve the consistency of your glaze results.

If you're not familiar with how to measure specific gravity, you can grab my free guide here.

Measuring specific gravity is the essential first step before you do any flocculating or deflocculating of your glazes. Once you know the water is where you want it, you can ask yourself the 3 questions above to decide if it needs to be flocculated.

What is a Saturated Epsom Salts Solution?

Epsom salts are my flocculant of choice. Other flocculants exist but Epsom salts are easy for me to find and they work really well.

Epsom salts, like the ones you can buy at the drug store and bathe in, are made of magnesium sulphate. If you live in another part of the world, they might not be called Epsom salts. Using the chemical name "magnesium sulphate" should help you find them.
A close up digital microscope shot of epsom salts on a green piece of paper.
To use Epsom salts as a flocculant, the salts need to be dissolved in water. This breaks up the bond between the magnesium and the sulphate so the magnesium ions are free to attach themselves to the clay particles.

A saturated solution is defined as a chemical solution containing the maximum concentration of a solute dissolved in a solvent. Additional solute will not dissolve in a saturated solution.

In our case, the solute is Epsom salts and the solvent is water. So a saturated Epsom salt solution will have the highest possible number of magnesium ions per volume of water.

When you add Epsom salts to water they'll dissolve and seemingly disappear into the liquid. If you keep adding more salts, they'll continue to dissolve until you reach the saturation point. At this point, no more salts will dissolve and they'll start collecting on the bottom of the container.

And that's how you know you have a saturated solution, when you have undissolved salts on the bottom of your container.

The reason why we want our Epsom salt solution to be saturated is because we don't want to dilute our glaze with more water. Remember, we've already determined that we have the right amount of water by measuring specific gravity. If our Epsom salt solution is weak, we'll be adding more water than necessary to the glaze.

The water is just a medium for carrying the magnesium ions into our glaze bucket, so they can attach themselves to the clay particles. We want maximum ions, minimum water.

When using the saturated solution to flocculate your glaze, you use the liquid on top and leave the undissolved salt crystals on the bottom.

I keep a labelled container full of saturated Epsom salts solution in my glazing area. If I ever notice there are no crystals on the bottom, I just add more salt to the mixture and stir.

How to Make a Saturated Epsom Salt Solution:

1. Grab a container with a lid that you'll store your saturated Epsom salt solution in. A clear container makes it easy to see if you have undissolved salt crystals on the bottom.

2. Fill the container with water.

3. Add some Epsom salts and stir.

4. Watch as you're stirring to see if all the salts are dissolving.

5. If all the salts dissolve and disappear, add more salts and repeat.

6. Once you have a layer of salt sitting on the bottom of your container, you know you have a saturated solution.

7. Always check for undissolved salts before flocculating. More salt can dissolve over time. If there aren't any, add more Epsom salts and stir.

8. When flocculating, use the liquid on top and leave the undissolved salts on the bottom.

Do I Need to Use Hot Water?

If you use hot water while creating your saturated solution, the salts will dissolve faster and more salts will dissolve overall.

Solubility (the ability to dissolve) increases with temperature. But when the water temperature comes back down to room temperature, the solubility will decrease and some of the previously dissolved salts will precipitate out of solution. Meaning they'll turn back into solid, undissolved salts.

This is perfectly ok because when we have undissolved salts at the bottom of our container, we know we have a saturated solution.

You don't have to use hot water when making your saturated Epsom salt solution but doing so will speed up the dissolving process. I do recommend using hot water if you're making the solution right before you're going to use it.

But then it'll cool over time and be room temperature every other time you use it. So if you only have cold water to start with, you'll be fine.

What matters more is that you have undissolved salts at the bottom of your container when you go to flocculate your glaze. That's how you know you have a saturated solution. (Have I driven that point home yet? Repeat after me... )
Re-crystallized Epsom salts. An undisturbed saturated solution will re-crystallize over time, espcecially with fluctuations of temperature.
How Much Epsom Salt do you Add to the Water?

You might want to know how much salt to add to a certain amount of water. You might think this would be something I would weigh out and measure carefully.

But I don't. I just add more than I think I need and stir. If there's undissolved salt on the bottom, I stop. If there isn't, I add more salt.

Since I'm always using it and filling it back up again, and water will continue to evaporate and salt will continue to dissolve and precipitate, I'm pretty cavalier about it.

The truth is, it doesn't normally take much Epsom salt solution to flocculate a glaze so even if it's slightly undersaturated, it will usually give the glaze enough magnesium ions to become flocculated.

If you don't like the idea of eyeballing it and would rather measure, then here's what Wikipedia says:

It would be a fun experiment to try it yourself and verify what Wikipedia says. Start with 100 mL (=100g) of water and 100g of dry Epsom salts in separate containers. Take the temperature of the water.

Add a spoonful of Epsom salts to the water and stir.

If all the salts dissolve, add another spoonful and stir. Once the salts stop dissolving, weigh how much dry salt you have left. Subtract that from 100 and you know how much Epsom salts you need to make a saturated solution with 100mL of water.

If you do this experiment, I'd love it if you would post your results in the comments section below or post in my free Facebook group. There are also some flocculating videos posted in the group that you may find helpful.

If this post helped or inspired you, please share it with others.

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How to Make a Saturated Epsom Salt Solution to Flocculate your Glazes - Sue McLeod Ceramics

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Flocculate... What Does That Even Mean? You may have heard this term "flocculate" in reference to glazes and thought it was a funny word but you've never really known what it means. Or you may have been told what it means several times and still...

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Glaze test tiles from first round tests. All John Britt ^6

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Homepage - Duncan Shearer | Studio Potter

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Duncan Shearer - woodfiring master, blues and greens in soda firing

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My journey in ceramics started when I was 16, at a night class run by the Auckland Studio Potters. But it wasn't until I started studying ceramics at tertiary level that I realised that I was hooked. For the last 22 years I've been a professional potter, developing my love of clay and fire.

Check out my Posts page for how my last woodfiring went.

The Pottery portfolio pages have also all been updated with my latest work with the newest pots featured first.

If you want to know more about me or find an outlet for my work then check out the Information page.

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Homepage - Duncan Shearer | Studio Potter

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Thanks for visiting My journey in ceramics started when I was 16, at a night class run by the Auckland Studio Potters. But it wasn't until I started studying ceramics at tertiary level that I realised that I was hooked. For the last 22 years I've been a professional potter, developing my love of clay and [...]

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Brian Gartside - his use of different colours and textures, piecing glazes together on one form, lots of technical information and articles

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About half of the few hundred test tiles made for glaze testing over the next few months. Made with the two clays I use the most, Mac'sMud Buff Stoneware and Whitestone. I'm also making a few from Primo Pro WMS2005B-Stoneware clay with speckle, and Primo Pro Atelier White Stoneware, as I have pieces in these two clays, and want to test my glazes first!

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Vessels. Testing my consistency of shape with 1kg, 1.5kg, 2kg, and 2.5kg of clay. Trimming different lids from the same thrown shape

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Underglazing beads for my 'Ode to a Nīkau' sculpture

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Kate Newby - beads

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Kate Newby

Born 1979, Auckland (NZ). Lives and works in Floresville, Texas (US)

Consisting of site-specific projects that form relationships with locations through actions, Kate Newby's work engages with a wide range of situations using every-day actions and materials in order to displace and challenge how contemporary art is exhibited, viewed, and archived. These projects draw directly from the locations in which they are presented, with Newby's work bouncing backwards and forwards between initial observations, the process of working, and the sites that she works in.

Newby received a Bachelor of Fine Arts in 2001 from Elam School of Fine Arts, Auckland, followed by a Master of Fine Arts in 2007 and a Doctor of Fine Arts in 2015. She has exhibited at the 21 st Biennale of Sydney (2018), the 1 st Brussels Biennial for Contemporary Art (2008) and the Sao Paolo Biennale (2004). Significant solo exhibitions include Yes Tomorrow, Adam Art Gallery Te Pātaka Toi (2021); I can't nail the days down, Kunsthalle Wien, Vienna (2018) and Let me be the wind that pulls your hair, Artspace, San Antonio (2017). In 2012 Newby was awarded the Walters' Prize, Aotearoa New Zealand's premiere contemporary art award, by international judge Mami Kataoka. In 2017 she undertook the prestigious Chinati Foundation residency at Marfa, Texas.

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Kate Newby Born 1979, Auckland (NZ). Lives and works in Floresville, Texas (US) Consisting of site-specific projects that form relationships with locations through actions, Kate Newby's work engages with a wide range of situations using every-day actions and materials in order to displace and challenge how contemporary art is exhibited, viewed, and archived.

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I needed a way to make lots of test tiles... quickly, with the least amount of clay

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October 2020 Update

I've simplified my test tiles. Now, the test tiles themselves are just simple slabs of clay. But I make test tile holders out of a strong clay.

Flat, Square Test Tiles

Flat test tiles cut from slabs are ideal. You can easily make them from any type of clay. No need to turn your clay into slip for casting. They can be easily covered by dipping them into just 20ml of glaze. They have a large surface area and photograph well. I make my test tiles by rolling out a slab of clay. Then I use a fork to make the texture. Finally I cut the slab into squares of 5x6cm or 6x6cm.

The only drawback of flat test tiles is that they don't show off surface glossiness very well. So I have added an extra step: Pressing the tile down into firm foam to create curved edges. With slightly curved edges, it's much easier to get reflections in the photo to show gloss.

Test Tile Holders

Ideally, glaze tests are not fired flat but rather upright at a slight angle so the glaze has a chance to melt downwards. Below you can see how I make test tile holders using a strong, groggy, high-fire clay body (in this case, Soldate 60). These holders are covered with kiln wash and can be reused. Given their shape, they can be "packed" very tightly.

Material Melt Test Tiles

One fun ceramic chemistry project is to melt various materials at different temperatures. There are two types of "melt tests"- the simplest being just throwing a material into a small dish and firing it, the more advanced version being making a ball of the material and melting it on a sloped surface and recording the degree of melt.

To make simple melt test tiles, I use this easy technique: Roll out a slab of high-fire clay, and cut into 6x6cm squares. Using a piece of high-density foam and a 4x4cm piece of wood, quickly press each square into the foam, creating a shallow dish. Once bisqued, these dishes can hold any type of crushed material for your next firing.

Test Tiles: Old Method

Below is my old method for making test tiles. I put a little extra time into making each test tile self-supporting, as I often stuck tests into other people's kilns.

I've tried all manner of methods for making test tiles- thrown, extruded, and slab. Each type has advantages, but I've finally come to the safest, most economical and useful method for my needs.

Assuming you have a fast way to make slabs, using this technique you can easily make a couple hundred test tiles in an afternoon.

Hand-rolled slabs work fine. The irregular edges can be saved and used to make the supporting triangles. To attach the supports I use dry clay trimmings and pure vinegar. The triangles are dipped into the vinegar slip for about two seconds, then wiggled into place on the test tile until the two slabs are firmly joined. (I have tried this with all of my clays, from porcelains to stonewares, without problems. However, your clay may differ.)

Just after joining, the test tiles should be covered and dried slowly for the first day or so. You may notice some cracking along the join line, but the join should be strong enough to last through bisque and glaze firings.

If you have casting slip, the fastest way that I have found to make test tiles is to make a slipcast slab using a large, flat plaster table. Supports are joined to tiles using the same casting slip.

These test tiles will not fall over (especially important as I often put tests in public kilns). They can be stacked very closely in the kiln, and the height can be varied by choosing either the long or short end of the triangular support. Because they are flat, they require less glaze for coverage (handy when using very small batches of material) but also show more area of glaze than an extruded column. The hole in the base allows the tile to be hung on a glaze bucket or on a display. I stamp the back of the tile with a code for the type of clay, and there is ample space to write information about the test using an underglaze pencil.

The tiles should be quite thick in order to better absorb and support thicker layers of glaze.

After dipping the face of the tile into a glaze, I dip one side (not the top) again in order to see different thicknesses. (Double-dipping the top of the tile often results in the thicker glaze running down into the thinner area, sometimes resulting in a completely even coat after firing.)

Using flat, square tiles I can dip twice while only using 20ml of glaze. This is especially useful when doing triaxials or biaxials using the syringe method.

The back of the tile has a lot of space for writing glaze information. Before firing use an underglaze pencil (I use Amaco Black Pencils), after firing a permanent marker can be used to record the date and temperature.

Another advantage of these square tiles is that they photograph very well.

For my purposes, the best size for a test tile is 6cm or 7cm square. This size is large enough to get a feel for what the glaze looks like, while small enough to be covered by only 20ml of mixed glaze (including a second dip).

Conveniently, the supporting triangles are half the width of the tile, which allows for first cutting the slab into 6cm or 7cm columns.

I know it seems really anal, but this cutting pattern saves clay and ensures the tiles all rest at the same angle, allowing for more accurate comparisons and tighter packing in the kiln.

Test tile dimensions

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I've simplified my test tiles. Now, the test tiles themselves are just simple slabs of clay. But I make test tile holders out of a strong clay. Flat test tiles cut from slabs are ideal. You can easily make them from any type of clay. No need to turn your clay into slip for casting.