Hi all Random question: yesterday an empty ceramic / porcelain dinner plate was accidentally dropped on a tiled floor from the dinner table. Amazingly, it did not break. It was picked up and set aside on the kitchen counter, where it remained untouched. After about 15 minutes, there was a loud cracking sound, and it split along a single straight line, causing about 1/3 of the plate to be broken off. I really struggle to come up with an explanation for this, given that there was no heating / cooling taking place, or other external forces being exerted... Any thoughts would be interesting.