And like every Friday, the weekly "A Taste of Physics" column is back — number 13.
This time: "Prince Rupert's Drops," and the effect of compression and tension on glass.
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Prince Rupert's Drops are formed when molten glass is poured into cold water and solidifies.
They are named after the Anglo-German prince who introduced them to England in 1660.
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The drops have two fascinating properties; we'll explain each one separately.
The head of the drop is extremely hard — so much so that even enormous pressure from a hydraulic press cannot break it (see video).
The scientific explanation is that upon contact with the water, the outer layer of the drop solidifies and contracts much faster than the inner core.
The intense compressive stress that the shell exerts on the core gives it remarkable strength and resilience.
The tail of the drop, on the other hand, is exceptionally fragile — but the interesting point is that breaking its tip shatters the entire drop into thousands of fragments.
The explanation is that the outer part of the tail solidifies immediately, while the interior continues to stretch until it too solidifies. This means the inside of the glass is under extreme tensile stress, much like a drawn arrow on a bowstring.
Breaking the tail releases all of that tension at once; it shoots through the interior of the drop at extremely high speed and shatters it completely.
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Beyond scientific curiosity, the study of these drops has been enormously valuable in the development of tempered glass and bulletproof glass.
Have a wonderful weekend, everyone 😍 🌷
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