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April 30, 2008
Glass teardrops with long tails, too tough to shatter with a hammer yet exploding into powder if the tip of the tail is snapped off – these were a curiosity that puzzled and enthralled London’s new Royal Society in the 1660s, and still intrigues materials scientists today, as Anna Marie Roos wrote in April’s Endpaper, “The Prince and the Popper.” In Samuel Pepys’s diary (now posted as a blog, with more leads in the comments), they are referred to as “chymicall [alchemical] glasses”; the French called them larmes de verre, glass tears. King Charles II apparently liked to use them as a practical joke, making them blow up in people’s hands—a 17th-century equivalent of the joy buzzer. You can read natural philosopher Robert Hooke’s own account of his early scientific investigation of the drops online in Micrographia, beginning on page 33:
Some of theſe I broke in the open air, by ſnapping off a little of the ſmall ſtem with my fingers, others by cruſhing it with a ſmall pair of Plyers; which I had no ſooner done, then the whole bulk of the drop flew violently, with a very brisk noiſe, into multitudes of ſmall pieces, ſome of which were as ſmall as duſt . . .
You can watch the same phenomenon right here, on YouTube, from the creation of the clear tadpole- or sperm-shaped drops—by dripping molten glass into a pail of cold water—to their explosive self-immolation. High-speed photography has now revealed the contradictory inner stresses that make the drops so paradoxical; it makes them no less magical.
(Annie Gottlieb) |
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