Making Plastic from Milk

Although we often think of plastic as being artificial and petroleum-based, but plastic can also be made from altering natural materials, such as milk. This PDF explains how to
create plastic from milk and vinegar.

The basic procedure is as follows:

  1. Gently heat 500mL of full cream milk in a saucepan on low heat, without boiling it
  2. Add food colouring if you want your plastic to be coloured
  3. Remove the saucepan from the heat, and add 150mL of vinegar
  4. Filter the mixture (I used paper towel draped over a funnel)
  5. Rinse the solid with a little water, then shape it into a ball
  6. Leave for a few hours until most of the water has drained out
  7. Shape the plastic and leave it to dry for a week

Casein is a naturally occurring protein found in milk. When heated, the protein unfolds, and the vinegar also changes the shape of the casein. The casein reacts to form a polymer chain, which is insoluble in the vinegar, so precipitates out as small blobs.

The photos below show: the milk with colour added, the ball of plastic set out to dry, and the milk after vinegar was added.

From 1900 to 1945, casein plastic was used to make buttons, buckles, beads, fountain pens, comb and brush sets, and even a jewellery set for Queen Mary!

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