To make some biodegradable plastic we have two possibilities, we can use either:
- cornstarch
- potato starch 

Each of them are completely natural ingredients and are widely used in kitchen. 

We followed the protocol, using those quantities: (to identify them, we have put specific tints in each plastic)

-Our first plastic was made of 5g of cornstarch, 2mL of glycerin and 100mL of water (purple)  

-The second was composed of 5g of potato starch, 2mL of glycerin and 100mL of water (light blue)

After having creating those two plastics with both types of starches and having flowed them into the hollow side of plastic picnicware forks we could observe some differences between them:

- The first one contained lumps during the heating and he had a jelly texture and on top of that we had difficulties to pour it into the mold. - The second was better because we were able to pour it easily into the picnicware and it didn't have any lumps.

We observed how thoses plastics evolved, letting them dry for a week. We noticed that the two forks were too brittle, too thin, they tore and deformed. This means we'll have to change the molds, and also to find a recipe which can make the plastics stronger. However, we decided that for our next experimentations we will use potato starch because it is easier to mold it.

-The first plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water,plus 5,O mL of oil (red)

-The second plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water plus 1,0 mL of oil (light green)

Then we poured them into the hollow side of plastic spoons. The texture was very easy to pour, also very sticky, but the red one wouldn't stay in place because of its oily texture. However, those plastics were waterproof. We tested that ability by putting a little bit of each plastic into a beaker filled with water and agitating it. We didn't notice any degradation even after 10 minutes.

Assessment :

After two weeks of drying, the two spoons were simply "gone" from their molds, they had dried and formed little flakes outside of the spoons. In our further experiments, we'll have to reduce oil quantities, if we still want to make it waterproof, and we have to find another way to mold our plastics.

To make those molds we simply used regular metal tableware, pushing them onto the pastes to obtain molds. Then we made twice the same plastic, using the basis recipe:

-The first plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water,plus 0,1 mL of oil (yellow). A part was put in the modeling paste molds, another part into the salt dough molds.

-The second plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water, without oil (dark green). As above, a part was put in the modeling paste molds, another part into the salt dough molds.

We didn't face any difficulties to put the plastics into the mold. Plus, even with the low amount of oil, the yellow plastic was still waterproof.

Assessment:

After one week of drying, we notices that the plastic which was into the modeling paste crinckled and shattered, but had a solid texture. Yet, the salt dough molds were a failure, because the plastic mixed with the dough and was impossible to demold. The choice was evident, the best type of mold is the mold in modeling paste.

So we made up several modeling paste molds, one for forks, one for knives, and one for sticks (we hoped it would be simpler to mold and dry). Than we tred to increase the basic quantities of potato starch.

-The first plastic was composed of 7g of potato starch, 2mL of glycerin and 100mlL of water(orange). It was put into the sticks molds.

-The second plastic was composed of 10g of potato starch, 2mL of glycerin and 100ml of water (baby blue). It was put into the cutlery molds.

-The third was composed of 15g of potato starch, 2mL of glycerin and 100ml of water (purple). It was put, as well, into the cutlery molds.

We noticed that the texture was easier to put into the molds, and we increased our production, being more effective than before. We tried to dry the plastic using a hairdryer, but it made the plastic, as well as the mold, melt. We took the plastic in our classroom in order to observe their evolution during the days.

Assessment:

This time, as we were able to observe the plastic dry during the week, we could see it started to retract and crackle. However, it had quite an interesting hard texture, especially the one with 10g of potato starch.

We imagined other moulding techniques during the week: like compressing the plastic with an another mold inside the first mold to prevent it from retracting. We can also try to place on top several layers of plastic, as it dries, or even don't put the plastic into molds and trying to obtain thick sheets that we could cut into cutlery. We even found some spoons silicone molds in a cookery shop that we could test.

So during the next week, we made other plastics. We added vinegar because its acidity should help to dissolve the starch into a solution (we needed to test that hypothesis).

-The first plastic was composed of 10g of potato starch, 2mL of glycerin and 100mlL of water (light blue). It was put into the silicone molds, then on a ceramic plate. We pressed some of the spoons with another mold above it.

-The second plastic was composed of 10g of potato starch, 2mL of glycerin and 100mlL of water, plus 3 teaspoons of vinegar (light green) . It was put on a ceramic plate.

It was easier to mold with the silicone molds, and making flat sheets of plastic was easier too. 

Assessment:

During the week, we saw that the silicone molds spoons retracted, but the ones which were pressed didn't dry so we got holes into the pressing molds, but it didn't work either. The blue plastic on the ceramic plate made a brittle, but clear, smooth and thin sheet. The vinegar green plastic became distorted but it was the perfect texture, nearly unbreakable!

We observed mould growing on some of the plastics. We believe it is normal given that the plastic is starch-based.

- 15g of potato starch, 3mL of glycerol solution, 100mL of water (yellow)

- 15g of potato starch, 5mL of glycerol solution, 100mL of water (electric blue)

- 15g of potato starch, 10mL of glycerol solution, 100mL of water (green)

- 20g of potato starch, 3mL of glycerol solution, 100mL of water (purple)

- 20g of potato starch, 5mL of glycerol solution, 100mL of water (orange)

- 20g of potato starch, 10mL of glycerol solution, 100mL of water (grey)

- 15g of potato starch, 3mL of glycerol solution, 150mL of water (white)

- Put 100 mL of water in a pan.
- Add 2 mL of glycerin and stir with the whisk.
- Next, gradually add 5 g of potato starch while continuing to stir, adding food coloring (optional).
- Heat this mixture until it becomes translucent. When it becomes translucent , continue to heat over low heat while stirring for 10 minutes.
- Pour this mixture (still warm and liquid) on a plastic support (or glass) on which it can easily peel off by spreading a thin layer on its surface. (later on, we will simply pour it into molds). 
- Make the plastic dry at room temperature for about a week.
- Once dry, the plastic can be taken off.

First we compared potato starch and cornstarch to find which one would allow us to obtain the best plastic. Then we made experimentations to find the perfect quantity of oil to make waterproof plastic. After we compared what sort of mold could be the best for our tableware and finally, we tried to adjust the recipe to obtain an hard plastic.

_{Background picture: Solène mixing the plastic while Louise is filming her.}

_{Icon: Solène mixing the plastic (again)}

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