Is there Plastic In milk? Well, sort of. You made a substance called CASEIN. It’s from the latin word meaning “cheese.” Casein occurs when the protein in the milk meets the acid in the vinegar. The casein in milk does not mix with the acid and so it forms blobs.
The milk will boil and being to form tiny lumps (called curds) in a clear liquid (known as whey…is the Little Miss Muffet rhyme sounding a bit familiar right now?).
The curds will form a blob at the bottom of a clear liquid. The blob is actually fat, minerals and the protein called casein (milk protein).
True plastics, called polymers, are a little different. Milk contains many molecules of a protein called casein. Many of these casein molecule chain together are a polymer. The polymer can be scooped up and molded, which is why plastic made from milk is called casein.
Wash the Blob with water and knead it until it gets the consistency of dough.
Now’s your chance to show off the artist in you: Mould the plastic into any shape you wish, then place it on the wax paper and let it dry overnight to harden.
The combination of heat and vinegar (acetic acid) causes the casein from the milk to
clump together and come out of solution (i.e. precipitate). Casein is an ingredient used in making plastic which is why the blob resembles plastic. This casein plastic hardens when the curds dry out.
Don’t underestimate the importance of what you’ve just done…casein plastics were commonly used to make glue, paints, and paper.
Here are some neat facts about Casein plastic…
• Casein plastic was one of the first plastics ever made
• The first plastics were developed in 1862
• Casein was discovered in the 1890’s by a German inventor, Adolph Spitteler
• Casein was used in England to produce: glues, pens, knife handles, and buttons.