https://x.com/rainmaker1973/status/1919396665469067534?s=46

(http://www.autoadmit.com/thread.php?thread_id=5720671&forum_id=2#48905389)

Prince Rupert's drops are produced by dropping molten glass drops into cold water. The glass rapidly cools and solidifies in the water from the outside inward. This thermal quenching may be described by means of a simplified model of a rapidly cooled sphere.[3] Prince Rupert's drops have remained a scientific curiosity for nearly 400 years due to two unusual mechanical properties:[4] when the tail is snipped, the drop disintegrates explosively into powder, whereas the bulbous head can withstand compressive forces of up to 664.3 kilonewtons (149,300 lbf).

The explosive disintegration arises due to multiple crack bifurcation events when the tail is cut – a single crack is accelerated in the tensile residual stress field in the center of the tail and bifurcates after it reaches a critical velocity of 1,450–1,900 metres per second (3,200–4,300 mph).[5][6] Given these high speeds, the disintegration process due to crack bifurcation can only be inferred by looking into the tail and employing a high-speed camera. This is perhaps why this curious property of the drops remained unexplained for centuries.[7]

The second unusual property of the drops, namely the strength of the heads, is a direct consequence of large compressive residual stresses⁠—up to 700 megapascals (100,000 psi)⁠—that exist in the vicinity of the head's outer surface.[2] This stress distribution is measured by using glass's natural property of stress-induced birefringence and by employing techniques of 3D photoelasticity. The high fracture toughness due to residual compressive stresses makes Prince Rupert's drops one of the earliest examples of toughened glass.

(http://www.autoadmit.com/thread.php?thread_id=5720671&forum_id=2#48905416)