Can you make glue from milk?

Cow's milk is healthy. Among other things, it contains proteins, water and fat. The proteins in milk have a special property: they can be used to make a glue. These so-called casein adhesives are often used to stick paper labels on glass bottles.

Before you get started

If you are experimenting at home:
1. Let your parents know and discuss the experiments with them beforehand.
2. Do not eat or drink at your workspace.
3. Wash your hands thoroughly before and after the experiment.
4. Be careful and cautious with the materials.

Graphic figure boy pouring liquid in flask

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Glasses, a glass of cow's milk, a pot, a few spoons, a funnel, a hotplate, a measuring cup, a piece of cloth, a glass, vinegar, baking powder, scraps of paper and a jam jar.

You will need

Cow's milk
Glasses
Tablespoon
Saucepan
Hotplate or microwave
Sieve
Measuring cup
Piece of cloth
Water
Vinegar
Baking soda
Paper and jam jars for adhesive samples

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Let’s get started!

1. Heat some milk

Carefully heat approx. 40 mL of milk in a saucepan or in the microwave. The milk must not boil but should only reach a temperature of 50-60° Celsius.

2. Mix milk with vinegar

Add a tablespoon of vinegar to the milk and stir the mixture well. The milk will flocculate.

Glass on which a sieve with a piece of cloth is lying. The curdled milk can be seen on the piece of fabric.

3. Filter the flocculated milk

Place a small sieve on a second glass and cover it with a piece of cotton fabric. You can use a piece of an old men's shirt, for example. Pour the flocculated milk over the piece of fabric and filter the mixture. The flocculated milk proteins will be collected by the fabric.

Glass with milk proteins, a little water and baking powder. Stir the mixture with a spoon.

4. Mix the proteins with water and baking soda

Scrape the protein mixture from the piece of fabric and pour it into a glass. Mix it with about a teaspoon of water and a teaspoon of baking powder and stir well until you have a creamy mixture.

A piece of paper spread with casein glue is attached to the jam jar

5. Stick a piece of paper on a jam jar

Take a piece of paper and apply a thin layer of protein paste ‏(= casein glue) to one side. Stick the paper onto a jam jar and allow the glue to dry thoroughly.

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