Display card of samples of 'Erinoid' plastic, c 1930s.
© Science Museum / Science & Society Picture Library
These samples of plastic for use in door handles are made of casein and were produced by Erinoid Ltd of Birmingham at Lightpill Mills in Stroud, Gloucestershire. Casein is a semi-synthetic plastic present in skimmed milk. A rennet is used to precipitate it out. The casein is mixed with water, dyes or pigments and drawn out into shapes for machining. It is then cured by immersing it into a solution of formaldehyde. The plastic is then suitable for use in making furniture handles, buttons and other decorative items. 'Erinoid' was the British trade name for casein formaldehyde in the 1920s and 1930s.