Prince Rupert’s Drops

Prince Rupert's drop is also called Batavian tears, Tzar’s tears or Dutch tears. They have been around for 400 years, first brought in 1661 by Prince Rupert from Europe for Prince Charles II as a token of friendship. This drop first gained interest because of its curious properties. You can hammer this drop on its head with a common hammer and it will be perfectly resistant to any crack but if you happen to snip its tail it will shatter with a pop noise within seconds.

Prince Rupert's Drop is named after Prince Rupert of Rhine, a German prince who has been associated with the development of this glass curiosity. According to legends, Prince Rupert enjoyed using Batavian’s tears as a practical joke, handing them to members of the court and then yanking on the tail so that the glass would explode in the hand of the poor unaware victim. One might assume that people grew wary and a little nervous about accepting presents from the fun-loving prince after that.

To make Rupert's drop all you need is a glass rod with a high thermal coefficient, which you have to heat till it melts and separates in the form of a bubble. Immediately put it underwater in a jar of water. The heating and later cooling of the glass drop in water causes the particular distribution of stress as it goes through compression in the exterior and tension in the interior. Contraction is good for resistance against cracking, but the tension is bad because the glass particles tend to fly apart when you pull them.

Understanding this high-speed photography is critical. It explains the explosive disintegration of the drop when snipped at the end and how it was fracture-resistant when hammered. Making measurements in such objects which have such complicated geometric figures demands a special type of photoelasticity that was first used by Professor Hillar Abenn from Tallinn, Estonia. Now, this small little drop of glass is the origin of various portable electronic devices, funny how everything originated from a drop of glass, isn’t it?