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by Chris Woodford. Last updated: August 2, 2023.

Static electricity can be brilliantly useful: photocopiers and laser printers wouldn't work without it. But think about lightning for a moment and you'll see it can also be pretty scary. Although static isn't harmful by itself, when large amounts of it build up and suddenly discharge you can get dramatic and dangerous sparks (it takes about 3000 volts to make a spark just 1mm long). Set off a spark where there's something flammable (such as gasoline fumes) and, before you know it, you've got yourself a fireball and an explosion. You don't need lightning-sized amounts of static to cause problems: even a tiny spark can be problematic in some situations. If static has built up on your body through walking on a rug, and you start handling delicate electronic components, the sudden discharge of current from your body can be enough to cause some very expensive damage. That's where anti-static products can help. Let's take a closer look at how they work!

Photo: Dangerous fires and alarming explosions can result when sparks ignite flammable materials; that's one reason why antistatic materials are so important. Photo by Yasuo Osakabe courtesy of US Air Force.

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Where does static come from and where does it go?

If you've read our main article on electricity, you'll know that static electricity is (as the name suggests) a kind of electric charge that stays in one place-it really is static. It's the opposite of current electricity (also called electric current), which is electricity that moves from one place to another along a definite path called a circuit.

Static generally builds up when insulators (materials that don't conduct electricity very well, like plastics, rubber, and so on) or insulated conductors are rubbed, such as when you rub a balloon repeatedly on your clothing. You'll sometimes see this referred to as the triboelectric effect-from the Greek word tribos meaning rubbing-though that fancy expression doesn't really add much to our understanding: it's not the rubbing that's important, but repeatedly bringing the different materials into contact (which rubbing achieves very effectively). You can read a full explanation in our article about static electricity.

Static electricity can be really useful and we harness it in all kinds of practical ways. When you take a flash photo with your camera, for example, you have to wait a few seconds for static electricity to build up in a capacitor (an electricity storage device). Once the capacitor in your camera is fully charged, a light comes on, and when you press the shutter button, the capacitor discharges rapidly through a powerful xenon bulb, creating a brief flash of light and often a surprisingly loud crack, like a mini bolt of lightning. What's happening here? To get rid of static electricity, we have to turn it into current electricity by creating a circuit. That's what happens in lightning: so much electric charge builds up in a cloud that the air between it and the ground no longer acts as an insulator. Effectively, the air suddenly turns into a giant circuit that becomes visible-as a lightning strike-as the electricity flows down it to Earth.

Photo: Above and below: Static electricity and electronics don't mix! Electronic components often come in anti-static bags (sometimes called "static shielding bags") with warning labels like these attached. The bags, which are a sort of smoky silvery color, are made of plastic with conducting additives mixed in. When they're sealed up, they form an outer protective case known as a Faraday cage. It's a basic rule of physics that there are no electric charges inside a hollow conductor (which is what a Faraday cage is), even when it's charged up on the outside. So a bag like this effectively protects its contents in transit.

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How anti-static products work

To stop static, you have to ensure electricity never has a chance to build up. In other words, you have to make sure there's an electric circuit of some kind to carry any electric charge harmlessly away. Anti-static products do this in all kinds of different ways, sometimes physical and sometimes chemical.

Physical methods

You've probably seen cars driving along with little black strips dangling down from the back touching the road. A car's metal body, riding on rubber tires, builds up a static charge as it drives down the road with air rubbing past it. The theory is that strips like this prevent static electricity from building up on the car body, reducing radio interference, electric shocks when you open the doors, and car sickness. Do these strips work? No, they're entirely useless. In the 1980s, English trading standards officers prosecuted a company for selling anti-static strips because they simply do not work as described: car tires are 10 million times more effective at transmitting static charges to Earth (New Scientist, 4 July 1985, p.63). But even if they did work, one thing is certain: to do anything useful, they must be connected both to the metal car body and touching the ground, completing an electric circuit between the two-and if they're dangling in mid-air (as many of them are) they're a complete waste of time.

Photo: An anti-static car strip. Look closely and you'll see a zig-zag of copper wire running across the surface. This is what supposedly carries the static electricity to the ground. In practice, although rubber is an insulator, car tires do conduct electricity to a certain extent, making devices like this entirely redundant. You can see an alternative (and somewhat clearer) photo on Wikimedia Commons.

If static electricity really is a problem on cars, imagine how much more of an issue it is on airplanes, flying at greater speed and with much more surface area brushing through the air. You may not have noticed, but many planes have little carbon-fiber rods or wicks placed at the back of the fuselage to concentrate static electricity into a point and discharge it more effectively. They also help to dissipate electric charges if a plane is struck by lightning in flight. There are some good photos of the wicks on a Boeing 737 on this page from aerospaceweb.

Photo: This very similar idea for an anti-static shoe is much more plausible, because plastic-soled footwear really does insulate and we all get static shocks from doorknobs from time to time. The idea is simple: a zig-zag pattern of conducting wire (red) runs underneath your foot (collecting charge from your body) to some discharge bristles, touching the ground at the back of your shoe. Artwork courtesy of US Patent and Trademark Office from US Patent 3,383,559: Antistatic footwear by Karl Oesterheld, May 14, 1968.

Static isn't just a problem for vehicles that move; it can affect moving people as well. If you have floor coverings made from synthetic fibers, you probably get a static charge every time you walk over them. That's not normally anything to worry about, but it can be a problem if you're working in an office with sensitive electronic or computing equipment. That's why, if you're soldering sensitive electronic components into a circuit, it's usually a good idea to wear an electrically conducting wrist-strap to carry any static safely to Earth. Factories and work places often use anti-static flooring (rubber mats or carpets) to save the need for everyone to wear straps. They look just like normal floor coverings, but they're made with a good proportion of electrically conducting carbon fibers dotted among the ordinary rubber or nylon (synthetic plastic) fibers.

Artwork: Anti-static carpets have conducting fibers woven into the ordinary nonconducting ones (woollen or synthetic). Sometimes the conducting fibers run through in straight lines; sometimes (as here) they're wrapped tightly round the nonconducting ones. The conducting fibers can be made from things like copper, aluminum, or steel alloys, wrapped in an insulating outer sheath. They're generally tiny so they don't detract from the carpet's overall appearance, but not so flimsy that they wear out quickly or cause problems during manufacturing. Based on information from US Patent 3,639,807: Low-static carpet by Thomas B Mccune, Hudson Wire Co, 1972.

Anti-static floors are cleverly designed so that they safely dissipate static charges without dangerously allowing stray voltages to electrocute people in the case of an electrical accident. How do they "know" the difference between electricity that should be stopped and electricity that needs to flow? One design uses very thin copper strands surrounded by even thinner plastic sheaths. If someone is electrocuted standing on one part of the floor, at a typical household voltage, the sheath is thick enough to stop the current flowing through the material and electrocuting other people nearby. But static electricity typically involves much higher voltages, so the sheath's insulation will fail in this case, and any current will flow away harmlessly through the copper strands to ground.

Photo: Take precautions against static when you need to handle delicate electronic components. Either ground your body (briefly touch something like a metal radiator or other properly grounded/Earthed connection) or wear an anti-static wrist strap if you plan to handle components and circuit boards for a while. The black wire you can see at the bottom runs from the conducting strap around my wrist to a ground connection.

Chemical methods

These are physical solutions to the problems caused by static electricity, but there are chemical solutions too. In fact, if you look through the US Patent and Trademark Office database, you'll find that the vast majority of anti-static "devices" are chemical additives or coatings designed to make materials less prone to the problems of static.

Anti-static spray coatings typically consist of a conducting polymer (plastic) and a solvent made from deionized water and alcohol. When the solvent evaporates, it leaves behind an invisibly thin conducting "skin" on the surface of the object that prevents static build-up. Some washing detergents also have additives to reduce static crackling in synthetic fibers (used in clothes made from materials such as polyester). They work by allowing the fibers to retain a little moisture, which makes them more electrically conducting and reduces the chances of static building up. Very simple-and very effective!

Photo: Anti-static plastic = fantastic! Here's one way that chemical additives can make plastics anti-static. In this case, the additive is made of polar molecules (ones with uneven electric charge, so they have positive and negative ends). 1) These molecules (shown here in red) migrate to the surface of the plastic with their negative ends pointing out. 2) Water in the atmosphere (H2O, shown in blue) also has polar molecules, whose positive ends are attracted to the negative ends of the additive. 3) The moisture forms a thin, electrically conducting film that acts as an anti-static coating.

Pipelines and hoses are another place where static electricity can cause problems. Static is a particular concern in pipes that carry flammable chemicals, but it can also be a nuisance in ventilation or cleaning pipes where a buildup of static can cause a gradual accumulation of dust and blockage. Most pipes are now made of plastics, which only adds to the problem. Anti-static pipes avoid static buildup either with conducting additives added to the plastic or a coil (or line) of highly conducting wire (typically something like copper) running through them. They can usually be connected to ground at intervals as well.

Putting additives in plastics can certainly solve the problem of static, but it may create other problems in the process. If a plastic is used as a food packaging material, for example, any additives have to be nontoxic and safe. Additives like carbon black may radically change the color of a plastic, affect its strength, or alter its physical properties in other unhelpful ways. So there sometimes has to be a degree of compromise between making a plastic anti-static and ensuring that it still performs well in other ways.

Photo: Anti-static hairbrushes like this are usually made from plastics with electrically conducting additives such as carbon black.

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Find out more

On this website

Books

For older readers

Hazards of Electricity and Static Electricity by BP Safety Group. Institution of Chemical Engineers, 2006. Covers the risks of sparks, explosions, flash, and blast hazards caused by static (and mainly aimed at the petroleum industry).

Electrostatic Hazards by Günter Lüttgens and Norman Wilson. Butterworth-Heinemann, 1997. Explains how static electricity accumulates and becomes a source of ignition and/or explosion.

For younger readers

Videos

CSB Safety Video: Static Sparks Explosion in Kansas: This interesting video from the U.S Chemical Safety Board (CSB) is a superb case study of the static-spark explosion and fire that broke out at Barton Solvents in Kansas in 2007. It shows how the fire happened, despite the firm taking conventional anti-static precautions, and how the risk of handling nonconducting flammable liquids can be minimized.

Articles

Patents

If you're interested in the nitty-gritty detail of how chemical anti-static products work, these patents might be worth a look:

US Patent 7,229,956: Antistatic cleaning wipes by David Bedford and Julie Brennan. Reckitt Benckiser UK Ltd. June 12, 2007. Describes pre-moistened cleaning wipes with antistatic properties. There's some useful discussion of the surfactants involved and their chemical properties.

US Patent 6,130,277: Rubber composition improved in anti-static property and pneumatic tire using the same by Nobuyuki Okamura et al. Nestec SA, Kao Corp, Bridgestone Corp. October 10, 2000 and US Patent 5,714,533: Rubber composition improved in charging property and pneumatic tire produced by making use of the same by Kazuya Hatakeyama et al, Bridgestone Corp. February 3, 1998. These two discuss the chemical composition of car tires with built-in antistatic properties and the tradeoffs that have to be made between low rolling resistance, good antistatic properties, effective grip, and other useful features.

US Patent 4,899,521: Antistatic thermoplastic/polyamide-polyether compositions and antistatic polymeric films made therefrom by Marvin R. Havens, W. R. Grace & Co. Issued February 13, 1990. Describes an anti-static film made from a blend of polyether block amide copolymer and an aromatic sulfonamide antistatic agent.

US Patent 4,214,035: Antistatic coated polyester film by John M. Heberger, American Hoechst Corporation. Issued July 22, 1980.

US Patent 3,639,807: Low-static carpet by Thomas B Mccune, Hudson Wire Co. Issued February 1, 1972. A typical anti-static carpet made from a mixture of conducting and non-conducting yarn.

US Patent 3,650,816: Additives for clothes dryers by Jerome Rudy et al, Lever Brothers Company. Issued March 21, 1972. Describes a chemical that you spray into clothes tumble dryers to reduce static cling.

US Patent 2,773,852: Production of anti-static plastics by Richard G Rowe Jr and Guiles Flower. Dictaphone Corp. This goes into quite a bit of detail about plastics suitable for making vinyl records, and how antistatic agents were added to the vinyl resin during manufacturing.

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Text copyright © Chris Woodford 2009, 2020. All rights reserved. Full copyright notice and terms of use.

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An easy-to-understand explanation of how anti-static coatings and similar products keep you safe by reducing static electricity and sparks.

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Most of the large-scale solar parks in the world are located in deserts. These landscapes provide ample vacant land and year-round sunlight for solar power production. Researchers have envisioned transforming the Sahara-the vastest desert region on earth-into a massive solar park that might have the potential of producing four times the world's present energy demand.

But, there's a major problem-dust. Gradual dust accumulation on solar panels can reduce their efficiency by almost 30 percent within one month of operation. For some context, solar power losses of only three to four percent on a global scale could mean an economic loss of at least 3.3 to 5.5 billion dollars. As climate change intensifies dust storms, there may be a rapid loss of solar panels' efficiency unless they are cleaned several times a month.

Pressurized water jets and sprays are the most common method of cleaning solar panels. To avoid the risk of staining and damaging the glass of solar panels, only pure and demineralized water can be used. The need to transport clean water to dry or remote desert regions with scarce water supplies accounts for 10 percent of solar parks' operations and maintenance costs.

While the global capacity of solar parks is currently above 500 gigawatts, researchers estimate that up to 10 billion gallons of drinking water are used every year just for cleaning solar panels. To put things in perspective, that amount of water can fulfill the annual requirements of approximately 2 million people living in developing countries.

"I was amazed at the sheer amount of pure water that is required for cleaning solar panels," says Kripa Varanasi, a professor of mechanical engineering at MIT (no relation to the author). "The water footprint of the solar industry is only going to grow in the future. We need to figure out how to make solar farms more sustainable."

Attempts to get rid of dust accumulation on solar panels by using dry scrubbing methods like brushes and air pressure risk damaging solar panels due to the surface getting scratched over time.

The inefficiency of current cleaning methods motivated Varanasi and his graduate student, Sreedath Panat, to invent a contactless cleaning system that can automatically repel dust from solar panels with zero water usage.

The new system uses electrostatic repulsion to zap dust particles off the surface of solar panels. While dust by itself is not a conductor, they found that applying an electric force or adequate voltage range through an electrode-such as a metal bar-that passes right above the solar panel's surface charges the dust particles resting on the panel. Next, an opposite charge is applied to a transparent film-similar to the ones used on phones and laptops-which is then installed on the system, allowing the glass surface of the panel to repel pesky dust particles.
[Related: Floating solar panels could be the next big thing in clean energy.]
This system can be used separately along with a solar panel cleaning robot. Alternatively, it is retrofitted along each side of the panel and functions on a small amount of solar energy. Varanasi and Panat wrote about their research in a recent paper published in the journal Science Advances.

In the past, NASA has used electrostatics for removing dust from solar panels on Mars rovers with the help of electrodynamic screens. However, that technology worked only because they were implemented in extremely dry conditions without humidity impossible on Earth. "It also requires expensive interdigitated electrodes that have a weaker force and cannot tolerate moisture," explains Varanasi.

That made the duo opt for a different method of using electrostatics for Earth-bound solar panel cleaning. They began by conducting experiments with different sizes of dust particles and discovered that the silica in dust particles absorbs moisture from the atmosphere.

"A charge on the dust particles comes from a thin layer of absorbed water that is only a few nanometers thick but still acts as a conductor. That enabled us to estimate the electric force of dust particles and remove dust particles between the sizes of 30 to 40 microns," says Varanasi.

This promising breakthrough for the researchers arrived after performing their experiments at a wide range of humidity levels from five percent to 95 percent. They then observed that humidity is the driving force behind making the system work.

"As long as the relative humidity is above 30 percent, this system is robust and works very well," says Varanasi. "We can apply this to most geographical areas and even the driest deserts because of dew formations in the mornings."
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The duo has created a lab-scale prototype that consists of a solar panel, a conductive surface, and a moving electrode attached to the top. But, this system still can't rid a solar panel of particles less than 10 microns in size.

"These tiny dust particles are the ones that create the shadowing effect on solar panels," he adds. "We are working on some more improvements to overcome that issue."

As the MIT engineers are preparing to make their new system scalable in the future, other researchers are working towards developing a solar panel coating technology to reduce dust accumulation. Inspired by the lotus leaf's self-cleaning properties, Germany-based researchers at Ben-Gurion University attempted to develop silicon-based, hydrophobic coating for solar panels. This could prevent dust from accumulating on the surface of solar panels and reduce the amount of water required to clean them.

As of now, a UK-based company, Solar Sharc, has already launched a dust repellent coating for solar panels. They use nanoparticle structures for transparency that are only a few microns thick. According to the company's website, the coating is self-cleaning and enables the formation of water droplets on the surface that can roll off the panels.

But Varanasi says the problem with a coating of nanostructures is that it could erode over time after withstanding dust storms and windy conditions. "The texture of the anti-soil coating on the solar panels' surfaces could then get affected and lose its transparency," he says.

Despite all the convoluted challenges involved in preventing dust accumulation on solar panels, engineers like Varanasi remain optimistic about developing the right technology for making the solar industry more environmentally sustainable.

"Water is a precious resource," he says. "If the solar industry is proactive and approaches this problem from a holistic view, it will not directly impact communities' access to clean water."

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