Casein plastics were introduced at the beginning of the 20th century, their starting material being the protein in cows milk, precipitated by the action of the enzyme rennin.
Although casein is readily moulded to shape under moderate heat and pressure, it does not produce a stable material for manufacture until it has become hardened by soaking in formalin (5% solution of formaldehyde in water) for a long period. Unfortunately, this causes much distortion so casein plastics are almost always produced by machining stock material such as sheet, rod, tube or buttton blanks (small discs). After machining, casein may be polished either mechanically with abrasives or chemically with a ‘dip polish’.
The manufacture of casein is a slow, batch process requiring the material finally to be hardened by immersion in formaldehyde solution – sections of about 25mm thickness requiring up to one year. Casein plastics are not readily moulded, although sheet can be pressed into a limited range of shapes, such as shallow bowls and candlestick bases, by ‘hot stamping’.
Manufactured under the trade name “Galalith” in a wide varieties of colours by such manufacturers as Jakob Bengel production came to a holt with the onset of World War II.
1970’s producerFrancois Schoenlaub. and his Jewellery label Guillemette l’Hoir made pieces of jewellery for the Paris sont au Musee des Arts Decoratifs.
Entirely black items are rare, but they make for a convincing Whitby Jet stimulant. If immersed in warm water, a sour milk odour is detectable.