Casein plastics were developed at the very end of the 19th century. Casein - milk protein - was ground into powder, then mixed into a paste which was then hardened by prolonged immersion in formaldehyde. Thick slabs could take nearly a year!
Manufacture of casein plastics began in Germany and France, where it was introduced as Galalith (from the Greek for "milk stone"). The new material was hard and took a good polish, and like celluloid, could readily be colored to imitate natural materials such as horn, ivory, and tortoiseshell. Casein plastic was used for articles ranging from jewelry to fountain pens, but found its special niche in the manufacture of buttons. It was produced under a wide range of trade names, "Erinoid" being one of the most prominent English brands.
For various reasons, casein's popularity was much greater and longer-lasting in Europe than in America. Conway Stewart and other English companies continued to produce colorful marbled fountain pens out of casein right through the 1950s, while American penmakers' used casein only sporadically, and not at all after the general adoption of celluloid in the 1920s.
Casein plastics production began to shut down in the 1960s, with most factories gone by the early 1980s. Limited production of casein buttons continues, and casein knitting needles are still made, prized for their tactile qualities - typically described as smooth, silky, and natural.
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