Milk rocks

Have you got spare milk powder from lockdown?

It works well in this activity.

Objective

To make a "rock" out of milk by separating out the protein from the liquid.

Materials

1 C full fat milk (you can use milk powder to make the milk. Expired milk powder works too.)

1 tablespoon white vinegar

Measuring spoons

Food colouring

Microwave

Fine sieve

Bowls

Paper towels

Chocolate or ice cube moulds (optional)

Method

Warm the milk in the microwave for 30-40 seconds.
If you want to use two colours, put half the milk in a different bowl.
Add 1 tablespoon to 1 C milk or 1 1/2 teaspoons to 1/2 C milk.
Add a few drops of food colouring to the milk.
Stir the mixture. The mixture will look a bit like vomit as the protein (solids) separates from the liquid.
Put a fine sieve over a bowl or the sink. Tip the mixture into the sieve to drain off the liquid.
Empty the solids onto a paper towel and wrap it up to absorb the remaining moisture.
Shape the solids into a shape or push into moulds. I used a mini Easter egg mould.
The shapes will need to dry for about 24 hours, depending on how big and thick they are.

The Science

Milk contains proteins. The main one is casein. In a process called coagulation, vinegar causes the casein to form together into clumps and separate from the liquid (also called whey).

Casein has many uses. It is the major component in cheese making. It is also used to make paint, glue and plastics.

Difficulty:

Time: 10-15 minutes plus drying time

Adult supervision: minimal

Dangers: those with allergies to milk check with a parent

Step 5: the protein separating from the liquid

Step 6: the protein with the liquid drained off