Exploding Glass: The Rupert’s Drop
A Prince Rupert’s Drop is so strong that you can hammer on one end without causing a crack, but watch out for the other end—it breaks easily and causes the whole thing to explode!
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Dropping a small bit of hot molten glass into cold water creates a teardrop shape with a long, thin tail called a Rupert’s Drop. When the hot glass hits the cold water, the outside part of the glass cools much more rapidly than the inner part. The results are a tremendous amount of surface tension and internal stress in the glass. Because of the surface tension, the round end can withstand blows by a hammer, and because of the internal stress, breaking the thin, fragile tail causes the entire drop to explode into a fine powder.
Prince Rupert of the Rhine is credited for discovering this glass oddity in the mid 1600s although it’s likely others discovered it first. The legend is that his cousin, Charles II of England would explode these drops in the hands of unsuspecting courtiers as a practical joke.
