Although most plastics and polymers are made from petrochemicals, several can be created from organic materials, including foods. For example, the dark coating that develops on pots and pans and resists your cleaning efforts so vigorously is a naturally occurring polymer made from hot cooking oil. A more practical demonstration for younger students is a soft, malleable plastic made by separating casein proteins from milk. It requires no special equipment, and the familiarity of the main ingredient makes it a memorable demonstration.
- 1 cup milk, whole or 2 percent
- Microwaveable measuring cup
- Microwave
- White vinegar
- Mesh strainer
Show More
Instructions
-
-
1
Warm the milk in a microwavable measuring cup until it is noticeably warm to the touch, approximately 110 F.
-
2
Stir in 1 fluid ounce, or 2 tablespoons, of white vinegar. The milk will curdle immediately into a loose lumpy mass and a puddle of lighter-colored whey.
-
-
3
Strain the whey from the curds and rinse the curds gently under warm running water.
-
4
Knead the curds into a single soft, pliant mass. Divide the curds up for the students to feel and manipulate. Have them make shapes, then leave the shapes to sit out and dry for two or three days until completely hardened.