Prince Rupert Drops

Actual drama and excitement in glass technology today when we experienced the explosion of a Prince Rupert Drop. This is a tadpole-like object of solid glass with a bulbous end tapering down to a thin twirl. When you break the top of the thin bit, the whole thing explodes (done in water, of course, but no less a bang for all that). This effect is caused by cooling the glass too rapidly so that stresses are frozen inside the tadpole-head. The eponymous grandson of James 1 brought these to England in 1641 and the king liked to get people to hold the bulb-end in a tight fist and then he would crack off the tadpole-end giving the subject a nasty turn, I would say, like an electric shock. Our tutor didn't risk that - though apparently the glass shatters into powder. Indeed, we have seen a trail of furnace glass dropped in a bucket of water then crunched to powder in the hand.

Fascinating stuff, glass.