Yes – you really can make plastic from just milk and vinegar!
First of all just measure out 120ml of milk (it can be any type, we used semi-skimmed). Either heat your milk in your microwave or in a pan on the hob. It needs to get to around 50 degrees C so 1 or 2 minutes in the microwave should do it.
Next add 2 tablespoons of white distilled vinegar to the hot milk and stir – you should see clumps start to form.
Sieve the mixture to remove the excess liquid. Remove even more liquid with a paper towel or piece of kitchen roll.
You should be left with a clump of plastic which you can mould and shape as you please. It should begin to set in an hour.
Plastics are polymers meaning they are made up of long chains of repeated molecules (called monomers). The monomer that we have used is called casein and is found in the milk. When the milk is heated the casein molecules unfold. Adding the vinegar causes them to reorganise into a long chain polymer – making it a plastic.
It might look quite different to the plastics you’re used to today but up until the end of World War II in 1945, casein plastics were commonly found.