Milk Plastic

Our science experiment for letter P week was Milky Plastic from 365 Science Experiments published by Hinkler Books. Sounds interesting, doesn’t it?


  • Full-cream milk
  • Vinegar
  • Eye dropper
  • Microwave safe container
  • Spoon

Before we started I asked Cutie Pie what he thought would happen when the vinegar and milk were mixed together and he said “they will make funny tasting milk.”

 Warm the milk in the microwave or on the stove. Warm, not hot. (number recognition, coordination)

 Slowly squirt vinegar into the milk and stir gently. What’s happening? (fine motor, coordination)

Carefully pour the milk on to your hand, making sure it isn’t too hot. It’s best to do this over the sink! What’s in your hands?

Observations: The milk became stringy when the vinegar was mixed in. Eventually it became a white ball that, per Cutie Pie, felt like soft plastic, almost like silly-putty. It was squishy. The liquid remaining in the bowl was yellowish in color, yet translucent (per Cutie Pie see-through-able).

What’s happening? Per the book “Milk contains a chemical called Caesin.” The vinegar separates the caesin, which is a type of plastic, from the rest of the milk.

Cutie Pie didn’t really like holding this in his hands, but thought it a very neat experiment and loved the almost immediate change in the milk? Try it!

365 Science Experiments published by Hinkler Books is one of my family’s favorite sources for experiments. This post about this experiment is solely to share a fun experiment and experience with this blog’s readers and has not been posted as a result of compensation.

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