Prince Rupert's Drop: Meet the Glass That Resists Hammering and Explodes with a Touch
Did you know there is a piece of glass that can withstand hammer blows, yet can explode into thousands of fragments with just a gentle touch? We are talking about the Prince Rupert's Drop: a strange name for one of the most interesting experiments and discoveries made with glass — one that still helps us understand modern technologies, like your cell phone screen.
How is this possible? The answer has everything to do with pressure, internal stress, and the physics of materials.
The Experiment That Became a Legend
It all starts with a simple process that requires high temperatures: you drop molten glass into cold water. Instantly, the exterior of the drop cools and solidifies rapidly, while the interior remains hot and takes longer to cool. This creates a structure with very intense internal stresses.
The result is almost magical: the external glass, which hardened first, compresses the interior that is still contracting. This effect creates an extremely hard 'shell' on the outside and a kind of time bomb on the inside. The drop reaches an equilibrium so tense that it becomes practically indestructible... until you hit its weak point — more precisely, the thin tail.
How the Prince Rupert's Drop is made:
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The Physics Behind the Magic
Let's decode what happens internally. The exterior of the drop is under compression. This means the surface molecules are 'squeezed' tightly together, making this part super resistant. The interior, however, is under tension; that is, the molecules are stretched and want to expand. This combination creates an internal 'battlefield' where everything is delicately balanced.
However, if this balance is broken, such as when you clip the tip of the tail, the accumulated energy is instantly released. The result? An explosion into a thousand pieces, with minuscule fragments flying everywhere. The collapse is so fast it seems as if the drop has been pulverized. It’s like a glass house of cards: on the outside, everything looks solid, but one wrong move is enough for everything to collapse.
Prince Rupert's Drop Vs. Hydraulic Press:
From the 17th Century to Your Cell Phone Screens
The origin of the curious name for this experiment is a tribute to Prince Rupert of the Rhine, who presented the drop to the English court in 1660. However, this marvel of physics didn't stay only in the laboratories of the past. The study of internal stresses inspired technologies you use every day, even without knowing it.
A classic example is tempered glass — the kind used in car windows, bathroom shower doors, and, especially, cell phone screens. The principle is the same: the glass is heated and then rapidly cooled from the outside in, creating a compressed outer layer and a tensioned internal core.
As a result, a material much more resistant to impact is created. And if it does break, it shatters into small, less dangerous pieces than sharp shards (science saving our cut fingers since the 17th century).
The Prince Rupert's Drop shows how science can be visceral, visual, and even poetic. It unites history, art, engineering, and safety — all in one small piece of glass with unexpected behavior. This type of knowledge connects us to the real world and the technologies we use all the time. It's not just about physics; it's about how knowledge transforms simple objects into incredible solutions.
You Can Also Have Visceral and Poetic Experiences
If you enjoyed learning about the history and physics behind the Prince Rupert's Drop, know that at Etapa SigmaCamp, you can experience incredible things like this firsthand, in real laboratories led by renowned professionals in the STEM field — Science, Technology, Engineering, and Mathematics.
Currently, registration for Etapa SigmaCamp 2027 is still closed. But you can sign up for our Newsletter to follow more content like this and be the first to know when the next edition of the biggest STEM camp for students in Brazil will take place!