100 Days of Science #13-- Making Plastic From Milk

My boys thought this experiment was pretty neat even though we weren't making REAL plastic.  They were still impressed that we could get a plastic like substance out of milk.

All three of my boys ended up reading in the book how and why this experiment works before we started the project so I didn't bother having anyone making any predictions but I was pleased that they cared enough to want to know all about it!

For the experiment we needed:

1 cup whole milk
4 tsp. vinegar
a pot and the stove
a mesh strainer

First we measured one cup of milk and poured it into our pan.

Then we heated the milk up so it was hot but not boiling. Then we immediately removed it from the stove.

We measured out our vinegar and added it to the milk, stirring for one full minute.

We strained the milk out over a bowl (though you could easily do this over the sink too).

Once we were sure all the liquid was out we turned our rubbery milk out onto a plate and the boys all wanted to touch and feel it.  It's soft and easily sculpted at this point.

Once they were done with it we set it aside to dry for the night and when we checked on it the next day it was harder and more like plastic.

By adding the vinegar to the milk, the acid in the vinegar causes the milk to separate.  The fats and casein protein are what makes your more solid pieces that feel rubbery and harden into a plastic like substance.

Casein molecules link up and behave like plastic; it's what makes cheese so stringy on a pizza.

I really wanted to re- try this experiment with the boys using lemon juice; which I know is also acidic but we didn't have enough milk for a second experiment.

Others in this series:

1. Bernoulli's Principle
2. Ecotarium Trip 
3. Air Molecule Experiment
4. Kitchen Science
5. Corn Maze Field Trip 
6. Birds of Florida 
7. Making Static Music
8. Un-Make It Monday
9. Wind Tunnel Experiment
10. Biomes Field Trip
11. Disappearing Coin Trip
12. Snuffing out a Candle With Baking Soda

Linking Up With: Wonderful Wednesdays,

Oh My Heartsie Girls WW 650 x 635


  1. This is the coolest idea ever! Pinned :)

  2. This next on our list to try. Has your family tried making an art project of sorts with the unmolded plastic yet? I wonder what the possibilities would be?

    1. We didn't even think of that.. do you think it would get smelly after a bit?

  3. Good question. We will give this a try and find out(:

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