The types of glass used for shop fronts, dedicated buildings and as part of structural glass facades need to be exceptionally strong to avoid shattering too easily.

This is often achieved using reinforcement, coatings and tempering processes, but one of the first examples of the latter was invented by accident and was seen as one of science’s greatest mysteries for hundreds of years.

Batavian tears, sometimes known as Prince Rupert’s drops were first widely discussed in around 1660, although glassmakers have quite possibly known about them as far back as the Roman Empire.

They are glass beads made by allowing a drip of molten glass to fall into a bucket of cold water. This causes it to rapidly cool and form into teardrop-shaped beads with long tadpole-esque tails that are paradoxically one of the strongest and weakest pieces of glass in existence.

As many demonstrations, both modern and historic can attest, the bulb part of the bead can withstand incredible impacts, including hammer blows and even bullets, with super slow-motion cameras capturing the bullet shattering on impact, leaving the tear largely untouched.

By contrast, the lightest touch of the tail end of the drop will cause it to explode into a shower of tiny glass particles.

Whilst they became very popular party pieces and talking points in the 16th century as many outlandish theories arose to explain the teardrop’s unique properties, it would take until Professor Srinivasan Chandrasekar’s groundbreaking work using high-speed cameras to explain how they worked.

The reason is that there is an inherent and extreme level of tension inside the drop itself with a mix of compressive and tensile stresses creating an equilibrium that is very hard on one side to disrupt and very easy on the other side.

The gradual development of knowledge of these drops would help create theories and experiments that would lead to the development of stronger safety glasses.