Twisted Shop Class » Shattering the Strongest Glass
xplosive glass drops demonstrate why your car windshield is so strong and safe. If you want a scientific display of the dangers of pent-up stress, Prince Rupert's drops are it. After the trauma of being dropped molten-hot into a bucket of cold water, these glass balls, named for a 17th-century amateur scientist, turn into bundles of high tension.
They're impervious to even the strongest blows, until you find their hot button: Flick the tail, and they explode.