Prince Rupert's Drops (or Rupert's Balls) are a glass curiosity created by dripping hot molten glass into cold water. The glass cools into a tadpole-shaped droplet with a long, thin, tail. The water cools the molten glass in such a way that it becomes tempered glass. In fact, the head of the drop can be hit with a hammer without breaking, but the drops disintegrate explosively if the tails are scratched. The internal stress within these objects can be demonstrated through the use of polarizing filters.
The drops were supposedly invented by Prince Rupert of the Rhine, grandon of James I and the nephew of Charles I of England. Legend has it that the king would often used the drops as a practical joke in his court. He would give a drop to a courtier and then break the tail, causing a small explosion in the hand of the surprised person.
As these were invented in the Netherlands, the French term for these creations is larme Batavique. They are thought by some to be an early precursor of bulletproof glass.
External links