Curious property of Prince Rupert's Drop glass

If you drop molten glass into a bucket of water, it will solidify into what's called a "Prince Rupert's Drop." According to this Corning video, the surface of the drop is in a state of great compression, while the interior is in a state of great tension. You can squeeze the bulbous part of the drop with pliers or bang on it with a hammer to no avail. However, if you snap off the hair-thin tail at the end of the drop, it'll shatter into dust. (Via forgetomori)


  1. These Prince Rupert’s pieces of glass played a role in the movie Oscar and Lucinda with Cate Blanchett and Ralph Fiennes; powerful movie.

  2. Pity you can’t actually see the “blows up into billions of tiny pieces” thing because of the glare on the water’s surface. We’ll have to take their word for it.

  3. #5, thanks for that link.

    I was wondering if the reason they did it in the bucket of water was to avoid microscopic shrapnel. Based on the second video, I’d say that was it. Any exposed skin would get hit pretty bad.

  4. Prince Rupert Drops are mentioned in the classic SF story, “Dune Roller” by Julian May. The story was dramatized on “Tales of Tomorrow”, an early TV series available on Netflix or Amazon (Tales of Tomorrow, Collection 2.) The story is stylish and effective, the TV adaptation, not so much.

  5. Does anybody have a high speed camera I can borrow for a 1/100 of a second? Oh and $200,000 so I can film it in zero G.

  6. I learned about Prince Rupert’s Drops from The Cure’s Robert Smith when I was 14.
    It’s been one of my favorite scientificals ever since.

  7. The guy in that video is just being a pansy. You can just hold prince ruperts drops in your hand and snap them. The dust is so fine that it won’t cut you or anything.
    These drops are basically like tempered glass but with a much steeper residual stress gradient from inside to out.

  8. But who was Rupert?

    Prince Rupert of the Rhine, Count Palatine and Duke of Bavaria, grandson of James I & VI, son of Elizabeth of Bohemia, the Winter Queen, and brother of Sophia, Electress of Hanover. He’s buried in the same vault as Mary Queen of Scots, Queen Anne’s 18 stillborn babies and a host of other tragico-romantic roadkill of the Tudor/Stuart era.

  9. also responsible for the REALLY unmentionable body piercing – not like his vanilla brother, Albert

  10. The Corning Museum of Glass in Corning, New York is one of the best museums I’ve ever been to. Anyone interested in glass technology or glass history will love it. I visited in summer of 2006 and enjoyed it more than any other museum visit I’ve had anywhere.

  11. I could be wrong but I think it has to be a bucket of oil, not water. So I was told by the guy who was making these at a fair.

  12. The video said the interior was in tension and the exterior was in compression.

    Is that correct? Wouldn’t the interior be in compression and the exterior be in tension because the exterior cooled first and presumably shrank and created tension, that compressed the core.

    I may be wrong. I know water expands on freezing but I thought it was unusual in that regard.

    richardsonjim (AT)

  13. Is that correct? Wouldn’t the interior be in compression and the exterior be in tension

    The exterior cools almost instantly while still in an expanded state. Meanwhile, the interior is still liquid and cools more slowly.

    The interior is attempting to contract, but is prevented from doing so by the exterior. The exterior is therefore under a compression force which is attempting to reduce its volume.

    The exterior is also pulling on the interior, preventing it from contracting. The interior is therefore under a tension force which is attempting to expand its volume.

  14. #3: And also the Peter Carey novel the film was based on.

    Prince Rupert himself was a particularly colourful character- a flamboyant mercenary, who used to go into battle with a white poodle (accused of being his magical familiar, and sexual partner). He apparently survived a shot to the head, and two trepannings, and retired from warfare to pursue scientific research.

  15. #29 – Thanks BEANOLINI. I was about to post an answer #3 UMGREG02 that Oscar & Lucinda is actually based on Peter Carey’s superb novel.

    If you’ve read the book you’d be disappointed by the film. Carey’s description of the Prince Rupert Drop is so much more powerful than the subsequent visual depiction.

  16. A well known prank in the glassblowing world is to slip one of these into someones back pocket and “pop” it. Loads of fun!

  17. #13, #18: Been done, apparently. Alas, the video was not to be found on the interweb.

    “Recently an examination of the shattering of Prince Rupert’s Drops by the use of extremely high speed video (or so called “stop motion” techniques) [1] done by Dr. Srinivasan Chandrasekar at Purdue University has revealed that the “crack front” which is initiated at the tail end, propagates in a disintegrating drop within the tensile zone towards the drop’s head at a very high velocity (~ 1450-1900 m/s, or up to ~4,200 miles per hour).”


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