The spectacular science of exploding glass

A Prince Rupert's Drop is a piece of drop-shaped glass that won't break when you hit the bulb — but tap the tail and it explodes in a shower of granules. Watch it in 13,000 frames per second (fps) to find out why.

When you drop molten glass into cold water, you get a curious object: a Prince Rupert's Drop, shaped like a teardrop with a long, wiggly tail. What's so curious about the Prince Rupert's Drop is that you can hit the bulb as hard as you like with a hammer, throw it against the wall, and yet, even though we think of glass as fragile, it will not break.

That is, until you hit the sweet spot. If you damage any part of the tail, just a tiny bit, the entire drop explodes outwards in a stunning display.

Although the drops have been around for centuries, the reason for this strange behaviour has only been discovered recently — and it can be discovered by watching the glass explode in slow motion. That's what YouTube science educator Destin of Smarter Every Day has done.

With help from Orbix Hot Glass and a pair of very fast cameras — one at 3000fps and one at 130,000fps — we can see exactly what happens within the glass to make it shatter so spectacularly.

It's incredible stuff. If you're going to watch only one science video this week, make it this one.