Sculpted Science: Turn Milk into Plastic!

 MAKING PLASTIC!

Have you ever heard that plastic can be made out of milk? If this sounds far-fetched, you may be surprised to learn that from the early 1900s until about 1945, milk was commonly used to make many different plastic ornaments. This included buttons, decorative buckles, beads and other jewellery, fountain pens, the backings for hand-held mirrors, and fancy comb and brush sets. Milk plastic (usually called casein plastic) was even used to make jewellery for Queen Mary of England! In this investigation we made our own casein plastic out of hot milk and vinegar.


All plastics are composed of molecules that repeat themselves in a chain, called a polymer. Polymers can be chains of either one type of molecule or different ones, which are linked together in a regular pattern. Also, in a polymer, a single repeat of the pattern of molecules is called a monomer, which can consist of just one type of molecule or include several different kinds.

Milk contains many molecules of a protein called casein. Each casein molecule is a monomer and a chain of casein monomers is a polymer. The polymer can be scooped up and moulded, which is why plastic made from milk is called casein plastic.