A number of sources have sprung up for making biodegradable plastic from non-fossil fuel materials. One of the more interesting ones is Materiom. I’ve started experimenting with some of these recipes.

The key ingredients in most of these are corn starch, agar agar (a seaweed extract), and sometimes gelatin (from animal parts). Glycerin (aka glycerol, glycerine) is often used as a plasticizer–adding more makes a more flexible plastic. It can come from a variety of sources. All of these things are basically edible and can be manipulated in the kitchen so making plastic with them at home is appealing (if you’re into that sort of thing).

Starting with Materiom’s very flexible and translucent simmered agar recipe. I’ve been cooking up some variations.

My observations so far:

• Agar is awesome. It dries very tough and is easy to vary the flexibility by varying the amount of glycerin used. It is highly water resistant while still being biodegradable–an hour submerged in cold water barely affects it. But it will degrade pretty quickly in boiling water. Unfortunately…
• Ager is prohibitively expensive to use in quantity–roughly $40 a pound in pound/kilo quantities.
• Corn starch is cheap at about $2 a pound but degrades quickly in cold water. It also swells during cooking into a thick goo that is pretty much impossible to pour. Too bad because its great for machining after fully dried.
• Gelatin is basically dissolved cow bones and pig skin and I’m just not interested 🙂
• Many recipes include the use of vinegar as a weak acid. But vinegar stinks! Don’t use it unless you want to be repelled by your final product. Use a little citric acid or even salt instead.  They will provide the free ions to give the reaction a kick without the smell.
• Since all of these recipes use water the results will shrink, sometimes dramatically,  as they dry out. This makes them hard to cast or mold.

At the moment I am working with a 90% corn starch (for low cost) and 10% agar (for water resistance) mix, with as little water as possible and a pinch of citric acid. A bit of stirring and a quick trip to the microwave and the result is a puck of plastic that looks like it could actually be useful for something at a reasonable cost. I will post more if I figure out something that is more useful than an excuse for playing in the kitchen.