May 17, 2017

"Prince Rupert's Drops are small glass structures resembling tadpoles that can withstand the blows of a hammer and yet burst into powdery dust if their threadlike tails break."

"They have been a source of fascination and mystery since they were discovered in the 17th century."



ADDED: Here's the WaPo article, "The head of this teardrop-shaped glass can withstand bullets."
Just melt some sort of glass with a high thermal expansion coefficient (i.e. glass that expands upon heating), such as soda-lime glass (the kind used in most bottles, jars and windowpanes), and let a molten drop fall into cold water.

The water immediately cools the outside of the melted glass into a solid, before cooling the inside. This results in strong compressive (or pushing) forces on the outside and strong tensile (or pulling) forces on the inside. The resulting tension, as Smithsonian noted, makes the glass strong, it also means the entire structure is not in equilibrium.

If the tail is broken, the pent-up energy from that tension is suddenly released and cracks shoot through the entire structure at 4,000 miles per hour, which is why the drop then shatters into such a fine dust.

37 comments:

JohnAnnArbor said...

Do you have Prince Rupert's drops in a can?

Quaestor said...

The Prince Rupert of the drops is the same Prince Rupert of the Rhine who led the Royalist forces against Parliament in the English Civil War.

vicari valdez said...

wow!

Achilles said...

There is an analogy with these drops to current leftist thought. Surprising density and durability from some directions and equally ridiculous head explosions in another.

Amexpat said...

I to learn at least one new thing every day. Made my daily quota by watching the video.

Rocketeer said...

This guy does an excellent job of explaining just what Prince Rupert's Drops are, and why they behave the way they do.

vicari valdez said...

Achilles said...
There is an analogy with these drops to current leftist thought.
5/17/17, 10:22 AM


LOL

Quaestor said...

This is more impressive than the vid posted by Althouse.

Earnest Prole said...

Can there be anything more American than watching a Prince Rupert’s Drop shatter a bullet?

This glass drop can withstand a speeding bullet, and scientists just figured out why.

Quaestor said...

This follow-up video is even more impressive!

The 7.62x39 round hits the "tadpole" head and shatters! Then the drop disintegrates, but the action starts at the end of the tail and goes forward toward the point of impact. ABSOLUTELY FUCKING FASCINATING!

SayAahh said...


Apropos of the latest news from DC:

Sigmund Freud, discussing the dissolution of military groups in "Group Psychology and the Analysis of the Ego" (1921), notes the panic that results from the loss of the leader: "The group vanishes in dust, like a Prince Rupert's drop when its tail is broken off."

Quaestor said...

Can there be anything more American than watching a Prince Rupert’s Drop shatter a bullet?

GUNS and SCIENCE! The perfect storm of American delight!

Except for the proglodytes of the kind who loathe Trump. They hate guns unconditionally and can't keep science and religion separated in their pea brains. No wonder they are such hateful sourpusses. No fun ever will make you that way.

Cath said...

Hmm those Chihuly squiggles look kinda similar to these drops... I wonder.....

HoodlumDoodlum said...

YT: Smarter Everyday - Prince Rupert Drop @150k fps

St. George said...

Check out the very entertaining videos on engineering by engineerguy Prof. Bill Hammack. He explains the science and manufacturing history behind things like soda cans and other household objects.

Angel-Dyne said...

This is so cool! How did I not know about these things? I'ze so ignint.

Stoutcat said...

What does Bill Nye have to say about this, I wonder.

Todd said...

A) That is cool!

B) Learn something new every day!

C) Now THAT is what the Internet is for! How many folks would never have been exposed to that (or the science) but for the Internet!

Levi Starks said...

I discovered these about 5 years ago. It got me started exploring lamp working.
Essentially making small glass beads ant the like with only a small torch.
The Prince Rupert drops are not that easy to make, when I was doing it my success rate was about 1 in 10 that would survive the plunge,
But they are every bit as amazing as the video.
To me the most striking aspect was that a fracture very far up the tail is still effective in causing a complete instantanious disintegration of the entire drop.
I recommend eye protection.

Levi Starks said...

If you to try making your own, it can be done with a propane torch, and any kind of glass fragments, I'm think you can buy glass rods from hobby lobby.

Quaestor said...

This glass drop can withstand a speeding bullet, and scientists just figured out why.

From the linked article: This gives the drop its incredible strength, but also means that the core is composed of glass under immense tension.

Tension or compression? It seems to me that the differential cooling would compress the material in the center, rather than put it under tension.

Inga said...

That drop is Trump. It's only a matter of time that his tail gets cut off.

Rusty said...

I imagine, Levi, that the drop has to cool evenly and be fairly uniform. There are many tons of pressure holding the drop together once it cools.

Todd said...

Quaestor said...
This glass drop can withstand a speeding bullet, and scientists just figured out why.

From the linked article: This gives the drop its incredible strength, but also means that the core is composed of glass under immense tension.

Tension or compression? It seems to me that the differential cooling would compress the material in the center, rather than put it under tension.

5/17/17, 12:12 PM


Actually both. The outside of the drop is under compression whereas the inside of the drop is under tension. This is due to the outside of the drop cooling first and locking in the drop shape. As the cooling works into the center of the drop, the outside can not compress any more as it is already cool so the center is under high tension. A brake at the tail releases the tension causing a cascade shattering of the entire drop but due to the high compression of the drop head, impacts there have "little impact".

So sayath the Internet!

Biotrekker said...

Science is AWESOME!!

Char Char Binks said...

Quaestor, I saw the movie Cromwell, starring Richard Harris as Oliver, Alec Guiness as King Chuck I, and Timothy Dalton as Prince Rupe. The movie had no mention of Rupert's drops, although the prince himself did drop.

CStanley said...

I think Inga's analogy is actually pretty good but I think her prediction is wrong. The Democrats (and anti Trump GOP) have shown no ability to learn that these direct attacks on Trump do not work.

great Unknown said...

Actual disintegration velocities have been measured at about 4,500 mph. The number used in the article is the velocity where the wave front, traveling through the drop, reaches a critical level and the crack begins to bifurcate exponentially, leading to the explosion.

Bad Lieutenant said...

Wonder if anyone has tried to mitigate the shock of the tail breaking. Muffle it somehow. Do it underwater. Use padding, clamps perhaps. Melt that tail so it falls off or separates calmly. Coat it with glue, wax, rubber, more glass, etc. Be fun to have a PR Drop that took a bullet and did NOT shatter.

Gospace said...

Hmmm.... Cast a whole bunch of them in layers in rubber, and lay the rubber over some kevlar. Seems you'd need a second shot in exactly the same spot to get to the kevlar. Just a random thought.

Todd said...

Bad Lieutenant said...
Wonder if anyone has tried to mitigate the shock of the tail breaking. Muffle it somehow. Do it underwater. Use padding, clamps perhaps. Melt that tail so it falls off or separates calmly. Coat it with glue, wax, rubber, more glass, etc. Be fun to have a PR Drop that took a bullet and did NOT shatter.

5/17/17, 2:08 PM


There are a number of videos of PR drops being shot with bullets and the bullets fracturing but the drop not. I viewed one that went up to a jacketed .38 Special.

Bad Lieutenant said...

I watched at least one where the bullet shattered followed by the drop shattering, likely by some random impact to the tail. I want to see the drop not shatter. Also even if it could take a frontal assault, you couldn't use them as is because obviously they have that tail and if you touch it Kaboom. So, how do you get a PR drop without a tail?

Gospace said...

Bad Lieutenant said...
I watched at least one where the bullet shattered followed by the drop shattering, likely by some random impact to the tail. I want to see the drop not shatter. Also even if it could take a frontal assault, you couldn't use them as is because obviously they have that tail and if you touch it Kaboom. So, how do you get a PR drop without a tail?


Rapid cooling in zero G?

Quaestor said...

Todd wrote: So sayath the Internet!

It seems to me the explanation is inadequate since it does not account from the flash of triboluminescence that propagates from the head to the tail just before the tail begins the disintegration cascade.

jaed said...

Seems to me that hitting it with a bullet would account for the light flash (not sure whether it's triboluminescence specifically), since that's a fairly metric shitload of kinetic energy hitting the glass when the bullet lands. It might not have anything to do with the drop shattering.

It would be interesting to see if there's a way of shooting the head, while protecting the tail from shrapnel.

Bad Lieutenant said...

Instead of letting the globe form and fall into the water with a tail, clip it off and let a round piece of glass fall in the water. No tail, no shattering? Or, no tail, no super strength?

But my speculation is pretty worthless. With the blessing, one day we shall know. That's why science.

Bad Lieutenant said...

One of them survived an AK round!