Plastic milk

Follow these instructions to make plastic from milk and learn about proteins and chemistry.

• 19 May 2006 | Updated 14 October 2011

• What you need
• What to do
• What's happening

What you need

To do this activity you will need:

• 100 mL milk
• 10 mL vinegar
• a saucepan
• a thermometer
• a rubber band
• a piece of cloth for straining
• a spoon
• paper towel for draining
• an adult to help.

 What to do

1. Warm the milk to about 50 ºC with an adult’s help. Use the thermometer to determine when the milk is at 50 ºC.
2. Add the vinegar and stir.
3. Use the rubber band to fasten the straining cloth loosely over the saucepan and strain the mixture through it.
4. Squeeze out as much liquid in the cloth as you can.
5. Put the squeezed solid on the paper towel.
6. Press small amounts into thin, flat shapes and leave them to dry in the sun for a couple of days.

What's happening

The substance you have made is called casein. Casein is the name for a group of proteins found in milk that are also used to make cheese. Casein is mixed with other ingredients to make a type of plastic that's used for buttons.

If you shape the casein you made into discs, you can use them for game counters or for decorating. If you make some holes in the middle of the discs you can use them as buttons. You can add colour by rubbing food colouring into the casein before it dries, or by painting the discs after they're dry.

For more fun activities, join CSIRO's Double Helix Science Club.