|Prince Rupert's Drop|
Christopher Merrett, The Art of Glass, 1662, p. 354
Also known as "Dutch tears" these are glass novelties, usually made about three or four inches long, shaped like a tadpole; round and bulbous at one end, tapering to a narrow point at the other. They are formed by dripping hot molten glass into a bucket of cold water. Once a drop cools to a solid, the bulbous end can easily endure a moderate hammer blow, yet if even the smallest piece of the tail is broken off, the entire object will immediately explode into a hail of tiny glass fragments. The explanation is that when the glass is forced to cool rapidly in the water, the outer layer contracts like a tight skin, holding the interior under great compression. Like a balloon, it remains stable as long as the skin is not compromised. When the tail is snapped off, a shock wave of cracks advances and encompasses the entire object. Once the compressive forces of the skin are released, the glass interior shatters.
|Prince Rupert of the Rhine|
And that which makes their Fame ring louder,
With much adoe they shew'd the King
To make glasse Buttons turn to powder,
If off the[m] their tayles you doe but wring.
How this was donne by soe small Force
Did cost the Colledg a Month's discourse.
As a teenager, Rupert fought on the Dutch side, but this was long after Neri had returned to Florence from Antwerp. Before Neri left, he presented Maurice, the Prince of Orange with two vessels made from his best chalcedony glass, "which delighted him greatly." Rupert fought under Maurice's much younger brother, Frederick Henry. A third brother had courted his mother when she was young, as the two families enjoyed close ties. It is an open question whether Rupert saw or held any of Neri’s work in the Dutch royal households, but he clearly did take a keen interest in glass.