Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet (2023)

For glassmakers, a “Prince Rupert’s drop” is simple to make but strong enough to shatter a bullet. The way a drop of hot glass cools in water is the secret to its strength. The physics that make the drop so tough have applications for thin, yet strong, protective surfaces. Formed of a glass teardrop that elongates into a skinny tail, a “Prince Rupert’s drop” looks like a delicate, clear tadpole. It’s easy enough to snap the tail, but the rounded drop at the top itself? It’s unbelievably strong. You can’t even break it with a hammer blow. When a glassmaker drips molten glass into cold water, it freezes into a bead with an extra long tail. Like Sauron’s One Ring, you can’t break it with a heavy blow from something as strong as an axe. You actually need the speed and force of a bullet to shatter it. The crazy part is that even a bullet can break apart when it hits the drop. (Check out the video at the top of the story from SmarterEveryDay.) The Science Behind the Magic When the bu ... Read full article.