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Plastic Milk Experiment

Turn milk into Plastic with this fun experiment!

Topics: Plastics, Polymers

Difficulty: Easy to perform and get results

Note: Parent Supervision is Required as hot materials are being used


  • Milk

  • White Vinegar

  • microwaveable/stove safe Bowl

  • Microwave/Stove

  • Measuring cups

  • Markers/cookie cutters/glitter/food coloring

  • Paper towels

  • A Hard surface that will not be damaged by dampness


1. Pour 1 cup of milk into the bowl

2. Heat the milk up in the microwave or on the stove until it is hot. Have a parent help you with this step. We microwaved the milk for 2 minutes and 30 seconds in an 1100 watt microwave.

3. Add 4 teaspoons of vinegar to the milk

4. Stir the milk for a few seconds. You should see white clumps start to form in the milk. These are called curds.

5. Stack four paper towels on your hard surface

6. Scoop out the curds from the milk mixture and place it on the stack of paper towels

7. Use the paper towels to push down on the curds to remove excess moisture. You may need to use extra paper towels to full remove all the moisture. Here, we have folded up the paper towel stacks and pressed them together to remove the excess liquid.

8. Once the moisture is gone from the curds, mush the curds together and shape them into any shape you want. At this point, you can also mix in food coloring or glitter to color the plastic. I added pink food coloring and shaped it into a heart.

9. Once you are done shaping and coloring the curds, let it sit for 48 hours, until the curds have hardened. This hardened shape is your plastic!

How it Works:

To understand what is happening in the experiment, we need to know what plastics are made of. Plastics are made up of molecules that repeat themselves called polymers. These polymers are long lines of molecules that are ordered in a repeating order. Also, in polymers, a single repeat of the pattern of molecules is called a monomer.

Milk contains a protein called casein. Casein is a monomer. When we add vinegar to the milk, the curds that form are made of casein. When we separate the curds and put them together, we are able to make chains of the casein, forming a polymer. This gives us the plastic that is formed at the end.

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