Turning Milk into Plastic

When you think about plastic, I bet you think of one of your favorite toys, the tv remote, or a water bottle. All of these things are great examples of plastic, but did you think of milk? I bet not!

First to understand how milk becomes plastic, we have to understand what plastics are made of. They are composed of millions of identical atoms, called monomers, all linked together in one big chain. Scientists can make plastic with many different methods, but it almost always requires an organic material. For all plastics, the basic method of production involves separating or distilling certain parts of your base material away until there are enough of the necessary atoms to begin the bonding process. After this, something can be added to the reduced substance to form a plastic. It's a little complicated, but those are the basics.

This brings us back to our original point— how can milk become plastic?

Well, in this instance, milk is our base. Milk contains a protein called casein, and this is what will become our plastic. Something to remember about milk is that it never goes well with lemon juice, because the milk will quickly begin to curdle. However, in this instance, we want those sweet sweet curdles! Vinegar will be the agent that we add to the milk to make it curdle and make the plastic. Let’s head on over to the experiment!

Experiment Steps:

1. Pour 1 cup of milk into a heat-safe container. A coffee mug works great!

2. Microwave your milk for about 1.5 minutes. The milk should be hot, but NOT boiling. Be careful when you take it out!

3. Carefully add 4 tablespoons of vinegar to the hot milk.

4. Stir for 1 minute and watch the curds form! It may smell a little funny.

5. Pour the mixture into a coffee strainer with a bowl underneath and separate the liquid from the curds. Make sure to get as much liquid as you can out of the solid!

6. Transfer your curds from the strainer to a paper towel and squeeze out as much of the remaining liquid as you can! This mixture is safe to touch with your hands, so get in there!

7. This step is optional, but if you want your plastic to have color, add food coloring!

8. The plastic will be clumpy, and to get rid of some of these, all you have to do is knead knead knead!

9. Once you have kneaded to your desired texture, you can use a cookie cutter or sculpt with your hands to get any shape you want.

10. When finished, let your project dry for 2 days minimum.

Then, voila! You have your Casein Plastic made with just milk, vinegar, and patience!

As mentioned previously, milk acts as our base organic material. When the vinegar is added, it lowers the overall acidity of the milk. This causes a chemical reaction, and makes the casein protein molecules bond with the water and fat molecules present in the milk. All of these bond together in a long chain to form a polymer!

Additionally, the extra water that is left over can be added to compost or diluted to be used in household potted plants. No waste!

• Some things that can change the outcome of the experiment are what type of milk you use, as well as how much vinegar you add.

• The lower the fat content of the milk, the less likely you are to get curds! This is because there is less fat present to bind the polymer together.

• The amount of vinegar will also affect the amount of curds you get. Try experimenting with more or less after you have this process down, but keep in mind that it won’t work if you stir in the vinegar too quickly!