Spontaneous glass breakage is a phenomenon by which toughened glass (or tempered) may spontaneously break without any apparent reason. I was drinking red wine mixed with some ice cubes in a clear-glass mug when this freak accident happened. The bottom fell out quite literally!
There was no sudden temperature change as the clear-glass mug was in steady state for more than 10 minutes. The temperature difference between ice (273 K) and room temperature (291 K) was only 18 degrees.
