Plastics, continued

I've managed to do a lot more work and gather a lot more information on plastics since my last post. Here is what I have learned:

The ideal method for making the casein (milk protein) plastic uses 2% milk. 1% works also, but may require some blending to get the majority of it dissolved. Just heat the milk to simmering and then add some vinegar. I forget the exact amount, but if you don't add enough to totally separate it within one minute, just add a little more (see my previous post on plastics for ideal measurements).

If you do not add some baking soda to dissolve it a little bit (don't add too much, or you get glue; again, fairly exact measurements should be in the previous plastics post), it will be very difficult to mold. Once the stuff is dissolved into a very thick goo, you can let it sit for a bit to make it less sticky (this also allows the vinegar/baking soda reaction to finish). I found that it is easiest to work with if you let it sit for around 10 minutes (in a humid climate, it might need more), then work it with wet hands. You should definitely knead it, to get the bubbles produced by the vinegar/baking soda reaction out (bubbles will weaken it). Since it tends to warp a lot when drying, the best use is to make a flat sheet of plastic (put weight on it while drying, but make sure it gets enough air for it to dry; good luck). At 1-1.5mm thick it is brittle enough to break easily, but strong enough to use as a guitar pick (I am not good enough to "rock out", so it may not handle more active playing). At .5cm thick, it is still brittle, but much harder to break. Much thicker takes a very long time to dry (I have a piece that is almost 1cm thick that is still not dry after 5 days). If you prevent the surface from drying for too long, it can mold (I was cycling between weight that restricted air access with open air drying with no weight), but it can easily be sanded off once it is dry.

Casein plastic is extremely easy to shape and cut with a Dremel tool. It is reasonable to assume that it could be shaped with a CNC grinding machine. With a Dremel, you can etch artwork into the surface of the pieces.

If you have a good coffee grinder (that you do not intend on using for coffee ever again), you can grind cardboard into a fluffy powdery substance (similar in texture to cellulose insulation; also, avoid breathing the dust). If you mix this with the plastic before shaping and drying it, it will be many times stronger and far less brittle. You will need to add some water when mixing, but only add as much as you need to keep it moldable (otherwise it will take too long to dry). You will need to add quite a bit of the ground paper fiber to get the strength indicated above, but even a little should make a difference. (I used cardboard from cereal boxes. It was a little lumpy, but worked fine. I also happen to know that corrugated cardboard grinds really well.) Using longer cellulose fibers should work even better (things like cotton or hemp should perform far better than the paper fiber).

Note that adding the baking soda makes this plastic mildly water soluble. You can fix this by soaking it in vinegar for a few minutes, after it is dry (you might be able to do this wet as well, but I have not tried it). Don't leave the paper plastic composite in vinegar for too long, because the paper wicks the vinegar in deep, and bubbles will form within the plastic from the reaction. After this, you have to let it dry again (a few hours or so). This makes it water resistant. More than a few minutes exposure to water will still soften the plastic (and it will probably warp while drying), but it will not make the surface slimy or make the plastic dissolve.


I also tried making plastic from wheat gluten (yes, that is the thing that some people are allergic too; I am not sure how exposure to the skin would affect someone with such and allergy, so be careful if you are one of those people). I extracted the gluten manually. First, I mixed white (not bleached) flour with water (you can use whole wheat flour, but it takes longer as there is more fiber to get out). You want enough flour that you end up with a thick doughy mixture. It should not be significantly sticky (if it is, keep kneading in more flour until it is not). Once it is kneaded out well, make a ball and put it into a bowl of water that entirely covers the ball of dough. You can refrigerate this, but you do not have to. After several hours, you begin kneading it again, in the water this time. You will notice the water turns milky (this is wheat starch and other non-gluten wheat products). The surface will start to become loose pieces that are slightly sticky and extremely stretchy. This is the gluten. It sticks to itself well, so if pieces come off, just stick them back on. When the water becomes really white, dump it out (you can actually collect this and evaporate the water to get wheat starch) and put new water in (or, if you have a fairly large bowl, you can run the water while kneading). Eventually, the ball will no longer make the water white when kneaded or squeezed hard. At this point, you have fairly pure gluten. This gluten can be kneaded into a ball and then flattened and dried. It tends to shrink a lot when drying and thus warps a lot like casein, and so should be treated similarly when drying. This should work with reconstituted gluten powder that can be bought at the store, but I have not tried it yet.

A good note here is that gluten reacts oppositely to ph levels as casein. In other words, if you soak it in a little vinegar, it will dissolve, while a base (like baking soda) will return it to the rubbery insoluble that it started as. I have a few experimental applications for this property that I will discuss in a future post.

This plastic is also fairly hard, but brittle. I have not tried making a piece thicker than 1.5mm, but that thin piece worked fine as a guitar pick. The color is translucent, dark brown, as opposed to the opaque ivory color of casein. The gluten plastic also held a lot of air bubbles. I don't know if these are removable without the use of a vacuum jar or similar vacuum device. This plastic is naturally water resistant, but like the vinegar processed casein, it will still become soft with more than brief exposure to water. It is also easily workable with a Dremel, or similar rotary tool.


My next experiment with plastic is a fairly common bioplastic (the above are also technically bioplastics, though you would probably not find them on a list). It is made from starch, vinegar, and glycerin. The vinegar breaks down the part of the starch that is not a good polymer, so that it can become a good polymer. The glycerine makes if flexible. The amount of glycerine determines the flexibility, so a harder plastic can be made with less, or a more flexible with more. See: http://www.instructables.com/id/Make-Potato-Plastic!/ Note that this is a good application for the starch removed from the wheat gluten.

Starch is easy to obtain, as is vinegar. Glycerin is a bit harder to find. So I have gone to efforts to determine how to make it. In short, you make lye from wood ashes. With lye, fat/oil, and salt, you make soap. The byproduct is glycerin (which is sometimes mixed into the soap, but not for this application). An interesting note is that if you add the right amount of methanol to the lye, you will get biodiesel instead of soap, still with a by product of glycerin. So, instructions for making biodiesel will be in my book as well.

Lord Rybec