Called Prince Rupert’s drops (different story altogether), the head of these tadpole-shaped pieces of glass are strong. Very strong. So strong in fact if you shoot the head with a bullet it won’t shatter. ,
But it has a fatal weakness. The thinner tail is brittle and easily shattered and due to the composition of the glass, if the tail is shattered the entire structure of the glass drop – including the otherwise superstrong head – will shatter.
Now scientists have discovered why.
Researchers used a microscope to map the stress distribution of the drops, which form when molten glass is dropped into water.
Their study revealed that the head of the drop has a super high surface compressive stress because when the molten glass is dropped into the water the outside layer instantly cools while the inside layer remains molten. When the outer layer cools it contracts while the hot inside layer continues to want to expand but is now encaged in a solid structure. Eventually the inside layer also cools but as the particles are restricted in movement due to the outer shell being solid they can only contract in toward each other, thereby creating a very high tension inside the head – in other words, it gets very hard.
However, crack the tail and the entire lattice instantly collapses as the energy generated from the disrupted molecules in the shattered tail travel up the body of the drop of glass through a central nerve path eventually reaching the head and exploding.
Talk about a Shakespearean fatal flaw.
Sources:
Scientists solve 400-year-old mystery of Prince Rupert’s drops (Phys.org)