system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does burned food stick to glass? What's it holding onto?
gpt
The proteins and carbohydrates in food are glue.

Old-fashioned methods of making glue used the long protein molecules in animal products. Long molecules help the glue stick to itself and the surfaces. Modern glue contents don't differ much from the old fashioned contents.

When you cook food too well, you evaporate the water  so the food glue hardens. The chemical reaction for glue to bind to a surface also increases with temperature. This caused the food to bind to metal and glass surfaces.

Glassware in particular can absorb and hold more heat than it's metal equivalents (due to it's greater thickness). This means it can transfer a lot more heat and burn/glue food to it easier than metal.

Nonstick surfaces do not react to form bonds with the food glue. That's what prevents the sticking.