Very interesting!

The same principle(though less extreme) is used to toughen, or temper, flat glass.
Heat to around 650 deg c , then rapidly cool with blasted air creating tension inside the glass.
Toughened glass is stronger than normal glass (the name's a giveaway!), but is susceptable to defects or impacts from sharp pointed implements.
One of the principle benefits is the fact it breaks into lots of small fragments that are much safer than annealed glass.