What makes glass keep popping and snapping after it's been broken?

Question

I recently broke an old pane of glass, and the pieces on the ground kept snapping and moving around for several minutes after I'd broken the glass.

Answer 1

Sounds like it may have been a coated glass and the coating was giving way allowing more of the glass to break. The coating actually puts the glass under stress.

Answer 2

Glass is technically like a liquid, and stress can cause lots of little lines to creep out from the broken parts and keep breaking. The particles in glass move around like they're liquid, so you keep getting the glass more and more broken (like a windshield that just keeps cracking more and more.) Solids pretty much just break and stay broken, but glass is a tricky, unpredictable medium, especially when it's old. Old windows are actually thicker at the bottom than the top because the glass flows downward. Or the glass was haunted (I'm kidding.) Either way, glass is fun and beautiful but often hard to work with and prone to shattering and weird cracks and bull's-eyes.

Answer 3

That's interesting. If the glass pane was in the sun before you broke it, I'd suggest that the sun had made the glass very hot, and the cracking and popping after you broke it was due to a release of stress from the expansion in that heat. Like the stove pops and creaks during its cooldown period, or logs that crackle in a fire because the heat is tearing them apart. Or a stove eye that pops every so often after you turn it off, because it's cooling down. I know of tons of examples of metal popping while it's cooling; even moving suddenly, especially a cookie sheet of mine that's always warping when it gets hot, and bounces back straight after it cools down to a certain temp. I've never seen glass do it, though. Very neat.

edit - Ooo, I just saw jeepdriver's answer, though, and his answer about the glass coating looks likely, too. I didn't think about that. Good job, jeepdriver.

Answer 4

air in the glass

Answer 5

probably because you were WALKING ON IT