Bioplastic Revisited

Undaunted by the difficulties encountered during my first experiment with a home-made bioplastic, I determined to keep on trying. The story so far: I’m hoping to be able to recommend to my readers a bioplastic that might be made easily from abundant or waste material, that can be substituted directly for an oil-based material, and that is biodegradable.

Now, obviously the simplest way to meet these requirements would be by desk research, but I decided that for once “seeing is believing”. I’m intrigued by the amateur bioplastic scene because this seems more likely to make a new contribution towards sustainability. I’m thinking that a resource-poor country could really benefit from a grassroots bioplastic revolution, so I’m less interested in high-tech solutions, and more in what can be demonstrated by stovetop hackers. This led me to attempt to make some ‘milk plastic’, but the results were less than satisfactory: I produced a material that exhibited significant shrinkage and distortion during drying, and that I found very difficult to mould, while producing parts of very limited strength. I did some additional research in an effort to find out what might have gone wrong, and discovered new advice that I should use a cheesecloth to squeeze excess moisture out from the curdled bioplastic, and then ‘knead’ the material for a while. This is at odds with the instructions I had got from the Smithsonian, which said to leave some moisture in, to prevent cracking. I’m finding most bioplastic recipes very vague, and in some cases contradictory. Experimentation is required!

Further reading revealed that the scientific name for ‘milk plastic’ is casein plastic. The Plastics Historical Society provide a good deal of information about its commercial use, and I was surprised to learn just how long ago it started, being patented in 1899. Galalith (sometimes marketed as Erinoid in the UK) was used to make buttons, pen barrels, knitting needles, knife handles, buckles…

Casein buttons

All kinds of useful gadgets. But mostly buttons.

What? That stuff I found to be about as durable as chocolate, and far more difficult to mould, due to shrinkage? How could that be strong enough to make knitting needles? The secret (as discovered by French chemist Auguste Trillat) comes from hardening it by soaking in a 5% formaldehyde solution for a long period. This isn’t something that you’ll find the stovetop bioplastic enthusiasts doing, and rightly so since formaldehyde is carcinogenic. Still, when so treated, the material becomes surprisingly durable; it polishes up well, and dyes very well, to produce some distinctive pastel colours that were characteristic of the interwar period.

If you do happen to soak your milk plastic in a 5% formaldehyde solution (for up to a year, for a piece 25mm thick) it turns rigid – but while doing so, the material shrinks and distorts. Fine moulding while it’s in the plastic state is therefore impractical and most Galalith products had to be machined from solid sheet or bar, rather as we do with certain low-volume production runs today. By 1928 a process was developed whereby the material could be moulded directly into buttons, which reduced cost and opened up possibilities for new shapes. Casein plastic buttons had found their niche, being better than other early plastics in terms of surviving the rigors of washing, dry cleaning and ironing.

I’m reminded of a (frankly awful) verse from 18th century poet and physician John Armstrong, whose tribute to Cheshire cheese (!) saw it described as “tenacious paste of solid milk”. If you’re a vegan, you probably don’t fancy the idea of your buttons or the handles of your cutlery being made from this particularly tenacious form of milk, but keep in mind that in 1899 materials commonly used in the manufacture of household goods still included ivory, bone and horn, so perhaps Galalith was the lesser of two evils.

The manufacture of goods from Galalith halted during the Second World War, when milk was needed for feeding hungry populations, and the development of new materials had rendered it largely obsolete by the time supplies were restored. Nowadays, only very low volumes of specialist buttons are made this way.

With all these limitations, we can forget about casein plastic being a sustainable solution. The need to harden it with a carcinogenic chemical is a major obstacle, while batch manufacture that takes up to a year (and still requires subsequent machining) just about disqualifies it. I turned my attention to starch-based biopolymers instead.

Meanwhile, the bioplastic ‘Volkswagen Polos’ that I had made using an ice cube took a week to dry right through, shrinking and distorting as they did so. The early 20th century solution to this would have been to start out with a much bigger lump of material, and to have machined it down to the desired shape after a long soak in formaldehyde solution. I chose instead to leave my failed experiments out in the garden to see how long it takes for the action of sun, rain and microbes to turn them into compost.

The ice cube tray VW Polo...

The ice cube tray VW Polo. The pale upper parts failed to fully set while within the mould cavity. Poor workability means this is no substitute for modern plastics.

...a disappointing bioplastic experiment.

When fully dried, much of the shape had been lost: a disappointing first attempt with bioplastic.

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