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When Milk Becomes Plastic

When Milk Becomes Plastic

June 9, 2021

Did you know that with a few household items you can create a moldable plastic out of milk? It may seem surprising that the liquid we use for dunking cookies, adding to tea, or eating cereal could be used to create sculptures. It’s true! Through the creation of polymers by changing the milk’s pH you can have a new media to try out for arts and crafts, and it only takes a few minutes!  

Items Needed:

-       Measuring Cup

-       Milk

-       Microwave and microwavable container

-       Coffee mug or heat-resistant cup

-       Measuring spoons

-       White vinegar

-       Paper towels

-       Spoon

-       Strainer

-       Clean, hard surface not damaged by water

-       Adult help


1.     With adult help, heat one cup of milk in the microwavein a microwave safe container  for about 1.5 minutes. You want it hot, NOT BOILING. Carefully remove from the microwave.

2.     Add four tablespoons of vinegar to the mug.

3.     Pour the hot milk over the vinegar. You should see the milk form white clumps called curds.

4.     Mix the vinegar and milk slowly with a spoon.

5.     Then strain the mlk through the strainer. All the clumps will stay in the strainer. Collect the clumps and place them on a stack of paper towels.

6.     Fold the paper towel over and press down on the curdsto absorb extra liquid.

7.     Knead the curds together to form a ball. What you have created is casein plastic!

8.     You can now color, paint, roll or use cookie cutters to shape the new plastic ball. After creating something, you can sit it aside to dry.

Wow! Milk fromPlastic! How Does that Work?

Curds form after adding milk to vinegar because the acid in the vinegar changes the milk’s pH(acidity) and makes the milk molecules called caseins unfold and reorganize into a chain shape. Milk was commonly used to create plastic ornaments from the1900s to the 1940s including buttons, beads, jewelry and fancy combs.

Plastics are made up of molecules that repeat themselves ina chain called a polymer. Polymers can be chains of one kind of molecule or different ones  all linked together in a pattern. Expand on this experiment by testing out different temperatures for the milk. Does the plastic form faster with cooler milk or slower? Does theplastic form at all?

Try another acid. Does the experiment work with orange juice, lemon juice or a few tablespoons of soda? Which ones work best to make casein plastic? Have fun experimenting with textures and timing to figure out what works best for your art!


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