Prince Rupert’s Drops a noted for their unique tadpole shape and ability to withstand direct blows from hammers and even bullets without the bulbous end breaking due to the impact. However, the secret to defeating the Prince Rupert Drop has been discovered; you just need a bigger bullet.

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The SmarterEveryDay YouTube channel ran a series of experiments on the Prince Rupert Drop, starting with the basics of hitting it with a hammer. They upped the ante by shooting it with a 22 caliber bullets, then using a .38 Special, and finally subjected the design to rounds from an AK.

While the Prince Rupert’s Drop stood up to the majority of the tests, once a tapered bullet was introduced that traveled at the proper speed, it was finally defeated.

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It is important to note that the Prince Rupert Drops from the early experiments did often break. However, it wasn’t the bulbous end that gave way.

These shapes are incredibly durable at their larger end, but vibrations through the tail can travel up through the drop, leading the entire thing to shatter into what appears to be a puff of glass dust. The claims about the Prince Rupert’s Drop were never that it was entirely unbreakable, only that the bulbous end was highly resistant to compressive stresses.

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The videos also captured a phenomenon known as triboluminescence, where the glass emits a flash of light after impact. It is the same light occurrence that can be witnessed when sugar is subject to similar stresses.