casein

Scope note: A natural phosphorus-containing protein found in milk, composed of amino acids Casein curds form naturally as milk sours, but it is also precipitated by adding dilute hydrochloric acid to hot skim milk. The curds are collected, washed and dried to form a white to yellowish powder. The dried casein is insoluble in water and alcohol but is soluble in carbonates and other alkaline solutions. For use, casein is soaked overnight in a solution with a weak alkali (ammonium carbonate, borax, or lime) to form a clear, viscous solution. Casein has been used as a glue and binder since earliest recorded periods. In the late 19th century, casein was made into a plastic by treatment with formaldehyde, used for small items such as buttons, beads, buckles, combs, cutlery handles, and knitting needles. They were often pigmented to simulate ivory, horn, or tortoiseshell.

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