It's Plastic, But You Can Eat It!

Really..?!
You know that plastics are everywhere.  There are probably a few plastic items within your reach while you're reading this article. Usually, the majority of what we know as plastics today are made from materials that are extracted from crude oil. We use many plastic products such as  in computers, toothbrushes and in every day home equipments.  

But have you ever heard of plastics made of milk? They are used to make buttons, decorative brooches, buckles, jewellery, fancy combs and even brush sets. Did you know that milk plastic was even used to make jewellery for Queen Mary of England? 

Let's try to make milk plastic out of hot milk and vinegar. First, heat one cup of milk in a pan for about 10 minutes. Carefully stir the milk using a spoon to ensure the heat is spread evenly. Then add 6 teaspoons of vinegar to the small bowl and stir it with a spoon for about a minute. By adding vinegar to the hot milk, white chunks should become visible in the mixture. The white chunks are curds. And the curds are actually milk proteins called casein.

The vinegar acts as an acid that will change the pH of the milk and causes the casein molecules to unfold and reorganize into a long chain, curdling the milk.  Finally, pour the milk through the strainer. Please be very careful because it will be hot! Left behind in the strainer is casein. Now just mold it into a shape or add some colour to it and it will harden in a few days.  

Now you can use them to make decorative items, toys or a brooch by adding a pin at the back. So there you go! Now you know how milk plastic is made. It's actually not to be eaten but it's good to know that it is safe and non-toxic. For example, wouldn't it be nice to know that things that go in your mouth, such as your toothbrush is made of milk plastic?

Maybe it sounds strange that plastic can be made from milk. This is why milk plastic is also called casein plastic!

You can also try this activity at Petrosains and have fun with our current theme, Nature's Kingdom!

Posted by Ayu
Learning Specialist, Petrosains