The principle of Rupert's tears

The literal translation of "Prince Rupert's Drop"-Prince Rupert's Drop

These tadpole-like "glass tears" will be formed when molten glass is naturally dropped into ice water by gravity. This kind of glass, commonly known as "Rupert's tears", has wonderful physical characteristics: the tears themselves are no different from solid glass, and the hammers are all safe and sound. However, if we grasp its slender tail and apply some pressure, the whole glass tears will burst, splash and smash in an instant.

The principle of Rupert's tears breaking is called "crack propagation", which stems from the uneven pressure inside: when the molten glass drops into ice water, the surface of the glass cools rapidly to form a shell, while the glass under the shell is still liquid. When the glass in the core also cools and condenses, due to the volume change, the liquid glass naturally shrinks towards the already solid shell, resulting in great compressive stress on the glass near the surface, while the core position is pulled around and subjected to tensile stress. When the exterior is damaged, these residual stresses are released quickly, which makes the cracks spread all over the body and fragmented instantly. According to the observation of high-speed photography technology, the transmission speed of the cracks can reach 145 -19 meters per second.

in addition, the distribution of pressure can be seen with a cross-polarized mirror: