Cow’s milk can be made into a variety of products including ice cream, yogurt, butter, and more, but did you know it can be made into jewelry? If you “got milk’ you can try this lab out and discover a new milky way of chemistry.
One cup of 2% milk
Four teaspoons of white vinegar
Stove-top oven and pan or a microwave and microwaveable bowl
A large spoon
Recruit an adult helper to heat and handle the hot liquids.
Heat one cup of milk in a pan on a stove top until it is hot, but not boiling. Alternatively, you can microwave the milk in a microwaveable bowl by warming it at 50 percent power for five minutes.
Have the adult helper pour the hot milk into the bowl.
Add the four teaspoons of vinegar to the milk and slowly stir with the spoon for a minute or two.
Carefully pour the mixture into a colander inside a sink. You should find that white clumps called curds are left behind in the colander.
When the curds are cool enough, you can rinse them in water and mold them into shapes. Let your plastic sculpture harden over the next few days.
Why it works:
Milk is a colloid consisting of many molecules of a protein called casein suspended in water. Each casein molecule is a small individual molecule known as a monomer. When the casein molecules are linked together, they become a polymer. The vinegar in our mixture acted as a cross-linking solution which helped the casein molecules link together in a process known as polymerization. Plastic made from milk is called casein plastic. Casein plastic was commonly used from the early 1900s until about 1945 to make buttons, beads, fountain pens, and other decorations.
In 1899, Bavarian chemist Adolf Spitteler’s cat supposedly knocked over a bottle of formaldehyde which dripped into the cat’s saucer of milk. In the morning, Spitteler discovered that the formaldehyde had solidified into the first casein plastic. It was a great meowment in history!