Prince Rupert's Drops

February 17, 2008 12:33 PM

Prince Rupert’s Drops are quickly cooled teardrop shaped glass pieces that have amazing physical properties. While tough on the big end, they will explosively shatter if broken on the small end.
posted by Tube (49 comments total)

After learning these things, I have a strong urge to crawl under my bed and hug myself to sleep.
posted by stresstwig at 12:54 PM on February 17 [3 favorites]

My glassblowing instructor made some of these to amuse us once. He was making a point about how glass isn't always what you predict it'll be. The point got across pretty well.
posted by crinklebat at 1:01 PM on February 17

Terrorism!

(Also, cool!)
posted by maxwelton at 1:14 PM on February 17

Shadooby! Thanks, Tube.
posted by hal9k at 1:20 PM on February 17 [2 favorites]

Cool stuff, thanks Tube!
posted by carter at 1:20 PM on February 17

Fascinating! If only Hooke could see his vindication...
posted by languagehat at 1:20 PM on February 17

... And if you ever get the chance, drop by the Corning Museum of Glass in upstate New York.
Lots of beeeyoootiful works and an excellent staff to help you understand this stuff...
posted by Dizzy at 1:29 PM on February 17 [1 favorite]

neat!
posted by andythebean at 1:30 PM on February 17

Wicked! (And is it just me, or do those drops look a lot like the creepy bug inserted into Neo's belly in the Matrix?)

You have to give Prince Rupert credit for being a pretty accomplished guy. Canadians know him as the first governor of the Hudson's Bay Company who gave his name to a few bits of the country, but he wasn't just a royal who fulfilled his duties as a soldier, he was also a decent amateur artist and scientist. Plus, he was briefly -- a pirate! (OK, a buccaneer, but close enough). The Wikipedia summary is a pretty good read.
posted by maudlin at 1:34 PM on February 17

super-cool
posted by dr. moot at 1:38 PM on February 17

I have never heard of this but I am astounded that Wikipedia claims this isn't where Julian Cope's band got its name.
posted by Slarty Bartfast at 1:50 PM on February 17

Oh yeah, very cool post, Tube.
posted by Slarty Bartfast at 1:50 PM on February 17

Groovy! So what would happen if you made a Prince Rupert's drop in zero gravity? Presumably the glass would form a perfect sphere, the outer layer would be totally impenetrable, and you'd therefore have some kind of super-indestructible ball-bearing?
posted by Chunder at 1:54 PM on February 17

Really interesting. Great post.
posted by middleclasstool at 1:55 PM on February 17

Am I the only one whose misread this as "Prince Albert Drops" and thus completely misgauged what this post was about?
posted by Admiral Haddock at 1:55 PM on February 17 [3 favorites]

These are neat. I think I've also heard them called somebody-or-other's tears, but I don't remember whose.

Chunder: I think so; you'd end up with more-or-less normal tempered glass, except in a sphere instead of the usual plate.
posted by hattifattener at 2:06 PM on February 17

> So what would happen if you made a Prince Rupert's drop in zero gravity?

Here's my guess: The tail has nothing to do with gravity, it's the product of the molten glass not fully detaching from the rod. If it's possible to drip a wad of molten glass into a bucket of ice water at zero G, there'd still be a tail.
posted by ardgedee at 2:28 PM on February 17

except, Slarty Bartfast, Cope gives the source of the name (a Marvel comic) in his autobiography.
posted by scruss at 2:33 PM on February 17

This is wicked. Much thanks for not making this a Mystery Meat YouTube post.
posted by Mitheral at 2:36 PM on February 17

Cool stuff, thanks!
posted by agentofselection at 2:41 PM on February 17

I worked in the commercial glass industry for about ten years. Glass is an amazing and treacherous material. Prince Rupert's drops show why glass in doors and many overhead places is tempered; it greatly increases the surface tension. That way, if the glass is broken it "explodes" into tiny and relatively unsharp bits - not large ragged shards that could seriously cut someone.

The only problem is that sometimes glass isn't quite pure and contains miniscule pieces of foreign matter that don't temper like the glass. They can cause stress points that will cause window and door glass to spontaneously rupture.
posted by Benny Andajetz at 3:06 PM on February 17 [2 favorites]

Pepys wrote about 'em. I forget where. Check the blog, dueds.
posted by Henry C. Mabuse at 4:16 PM on February 17

Here's my guess: The tail has nothing to do with gravity, it's the product of the molten glass not fully detaching from the rod. If it's possible to drip a wad of molten glass into a bucket of ice water at zero G, there'd still be a tail.

But where would you get a bucket of ice water in space?

Actually, I bet that you could make tempered glass balls pretty easily, right here on earth.
posted by delmoi at 5:27 PM on February 17

And they soothe your throat and stop your cough.

Good read, thanks.
posted by HVAC Guerilla at 6:05 PM on February 17

ardgedee writes "Here's my guess: The tail has nothing to do with gravity, it's the product of the molten glass not fully detaching from the rod. If it's possible to drip a wad of molten glass into a bucket of ice water at zero G, there'd still be a tail."

The molten glass blob would form a sphere from surface tension after it was released from the rod. Obviously one wouldn't be able to just drop the glass into water at that point. An apparatus would be needed to detach the blob and direct it to the water quench.
posted by Mitheral at 6:23 PM on February 17

Alright, any glaziers on MeFi know how to make these? I can get a torch and a bucket of water; what kind of glass do you need?
posted by TedW at 6:28 PM on February 17

This is fascinating. Also, it gives me a name for a song I had been writing: "Why do Teardrops Explode?"
posted by eclectist at 6:29 PM on February 17

Never mind; Wikipedia led me here.
posted by TedW at 6:30 PM on February 17

Fascinating; I just assumed the glass would simply break off its tail. I neither expected an explosion, nor anticipated its enormous strength (on the "drop" side).
posted by Civil_Disobedient at 6:44 PM on February 17

I discovered through Oscar and Lucinda (both movie and book are terrific, although I would recommend above all reading the touching, clever and wonderful book by Peter Carey first)
posted by Auden at 7:20 PM on February 17

Anyone tried this trick? Apparently, lightly throwing a bit of broken sparkplug porcelain at a car door window can shatter it.

An explanation:
http://community.discoverychannel.co.uk/eve/forums/a/tpc/f/95010646/m/429100062

In brief, the tempered glass in the window is just like the glass in a Prince Rupert's Drop, the center is under tension and the outside is under compression. When you impact the glass with a sharp point, like that of a porcelain shard, it nicks the glass. Stresses in the local area pull or push on that nick, and cracks can now propagate from that area, spiderwebbing accross the entire pane of glass.

The front windscreen of a car is laminated to prevent this.
posted by sebastienbailard at 7:24 PM on February 17 [1 favorite]

Heh, cool! I produced this piece at the Museum of Glass when I worked there years ago, I can't remember if I was the one who shot the footage, but I certainly remember editing and playing it over and over in our amphitheater. A great demonstration the glassblowers used to do was make a prince rupert's drop, have a kid come down and put it in his gloved hand and explode it like that. The Museum of Glass was a pretty fun place to work, taught me a lot about a medium I never thought that much about previous.
posted by crunchywelch at 7:30 PM on February 17 [11 favorites]

Not to be confused with Prince Albert's drops, which tend to form on the toughened end (or so I hear)
posted by 5MeoCMP at 7:43 PM on February 17 [1 favorite]

On preview, what Admiral Haddock said earlier (dammit!)
posted by 5MeoCMP at 7:45 PM on February 17

Anyone tried this trick? Apparently, lightly throwing a bit of broken sparkplug porcelain at a car door window can shatter it.

Some folks call em 'ninja rocks'.
posted by whatisish at 8:17 PM on February 17

And they soothe your throat and stop your cough.

Or... the next generation of Pop Rocks?
posted by greatgefilte at 10:07 PM on February 17

What an explosively good post!
posted by wastelands at 10:34 PM on February 17

Jesus christ I love this universe.
posted by cortex at 10:45 PM on February 17 [1 favorite]

Thank you, Tube. I am edified.
posted by mumkin at 12:21 AM on February 18

Jesus christ I love this universe.

Yeah, it's way better than the last one. Now if we can only manage not to implode it this time...
posted by Aquaman at 12:24 AM on February 18

But does it flow?
posted by OneOliveShort at 2:51 AM on February 18

They're not as easy to make as they look, BTW.

(And no, it doesn't flow - glass is an amorphous crystalline solid.)
posted by alby at 3:16 AM on February 18

Chunder - thinking about it, I don't reckon you could make something like that... when making one of these, the outside hardens & shrinks, forcing some of the material from the inside out (presumably into the tail), then as the reduced amount of interior material hardens it finds itself under tension and pulls in at the now hardened exterior, leaving it in compression... in a perfectly uniform sphere, as the outer shell hardens and contracts, the interior material has nowhere to go and is compressed... there'll be stresses introduced, sure, but I doubt they'd be anywhere near large enough to produce this effect...
posted by russm at 3:38 AM on February 18

I don't think it works that way. The interior pulling at the outside wouldn't provide a compression force. Scale it up to a sheet of glass 3m wide. There isn't flow to the edges, they don't even try to prevent the edge from cooling first during the tempering process.
posted by Mitheral at 4:07 AM on February 18

Peter Carey wrote about these in "Oscar and Lucinda", and I always meant to look it up. Awesome post!
posted by indienial at 2:36 AM on February 19

Wow, I imagine quite a bit of harm could come to your little brother, if you were to have fed him a few of these, oh say, about a half hour ago. Any recommendations for how to treat such a case, were it to hypothetically happen?
posted by Eideteker at 10:42 AM on February 19

Wow. I didn't expect the drops to turn into dust.

The article mentions high-speed photographs. Anyone got a link to a super-slo-mo video?
posted by five fresh fish at 3:13 PM on February 19

Oh GLASS...and here i thought we were talking about rain.
posted by salishsea at 6:01 PM on February 19

Late to the game here, but this is just too cool to not comment on. Thanks Tube, I had never heard of these before.

And suddenly I have this urge to write some kind of story where one of these is used as an untraceable murder weapon, kind of like an icicle dagger or something.
posted by quin at 10:17 AM on February 21