Galalith

Galalith is casein plastic that has been hardened in formaldehyde. Casein on its own is a protein solid that swells and softens in water. Formaldehyde cross-links the protein chains — it reacts with amine groups on lysine side chains and bridges one chain to the next — and the result no longer dissolves, no longer softens, and can be cut, turned and polished like horn.

That single treatment is the whole difference between a kitchen curiosity and the material that made most of Europe's buttons for fifty years.

This blueprint handles formaldehyde directly and is gated 18+ for that reason. Formaldehyde is a known human carcinogen, it is an acute respiratory and eye irritant, and formalin is a sensitiser — repeated exposure can produce a permanent reaction to it. The hardening bath is not a step to improvise: it needs a fume hood, correct gloves and a plan for disposing of the used solution. If you want the chemistry without the hazard, make the unhardened version instead and read the last step here for what the hardening does.