Activity Title: Make Toys From Milk
Did you know that over 100 years ago, royals would wear plastic jewelry made from milk? This fun activity will show you how to create plastic from milk known as casein plastic.
What do I need?
For this activity, you will need the following items:
1. A stove top or microwave to warm the milk
2. Milk (lower fat content is better)
3. White Vinegar or Lemon Juice
6. Strainer (or can create your own using cheese cloth or similar)
7. Paper towel
8. Lego Molds (any other mold will work too!)
How do we do it?
1. Measure out 1 cup of milk and heat on the stove top or in the microwave till it starts to steam.
2. Remove from the heat and add 4 tsp of vinegar or lemon juice. Stir gently.
3. The amount of vinegar is not exact. We used 4 tbsp by accident and it was fine, just made for a more intense vinegar smell!
4. You will notice that it immediately begins to curdle. Continue to stir gently for approximately one minute for all the curds to form. It’s important for the chemical reaction that you stir gently!
5. Strain off the liquid (whey) using a strainer or cheese cloth. You can gently press the curds on the strainer to get all the liquid out.
6. Now remove the curds and place them on a few layers of paper towel. Carefully pat and squish to remove as much liquid as possible.
7. Next, put the curds in the lego molds and leave it to dry.
8. The drying process takes time, approximately 2 days depending on how much moisture you removed with the paper towels. But you can remove it from the silicone molds after 24 hours and this will help speed up the drying time.
9. Next, paint your creations in the color of your choice using either markers or acrylic paint. Spray them with a clear coat to give them a nice shine!
10. Enjoy your new casein plastic toys which will last for up to 2 years. Pretty durable right?
What is the science behind it?
Milk contains molecules of a protein called Casein. During this reaction between warm milk and acid (from the lemon juice or white vinegar), the casein molecules unfold and form long chains called a polymer. The polymer can be molded and shaped which makes it a plastic. In this case it’s called casein plastic or milk plastic because of the type of molecules that created the plastic!