

Prince Rupert's Drop - huhtenberg
http://en.wikipedia.org/wiki/Prince_Rupert%27s_Drop

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huhtenberg
1\. Drop molten glass in a bucket of water.

2\. Let it cool down, take it out.

3\. Hammer the head of the drop and it won't break.

4\. Nick the thin tail and the whole thing will _explode_.

Here's a GIF - <http://i.imgur.com/opyMkMx.gif>

Here's the vid - <http://www.youtube.com/watch?v=xe-f4gokRBs#t=104s>

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gvb
Also discussed and illustrated in "The Curious Properties of a Molten Glass
Blob Dropped in Cold Water" <https://news.ycombinator.com/item?id=5440179>

The story linked is just a blog wrapper on a "Smarter Every Day" episode,
which is definitely worth watching.

Smarter Every Day: <http://www.youtube.com/watch?v=xe-f4gokRBs>

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cheez
Worth subscribing for two reasons:

1\. That guy's smile always makes my day better. 2\. You learn cool shit.

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borlak
Also consider subscribing to:

TheRoyalInstitution (science stuff, professionally done)

periodicvideos (excellent channel, chemistry stuff)

numberphile (math)

minutephysics (physics)

sixtysymbols (physics/math stuff)

DeepSkyVideos (space stuff, not updated often)

psyfile (psychology, not updated often)

engineerguyvideo (was really good, now rarely updates)

computerphile (brand new channel, no content yet, from same guys as the other
*phile channels)

and for fun: JoergSprave (the slingshot guy, but his creations are quite cool
if you like physics)

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scoot
Also the reason why Gorilla glass, which is mechanically similar (even though
the production process is different), is extremely impact resistant but can
fail catastrophically if nicked.

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raverbashing
Actually Gorilla glass is chemically treated for better resistance

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oneandoneis2
Yes, but the chemical treatment works by setting up the same kind of internal
stresses - IIRC, it replaces the Sodium atoms in the glass with Potassium, and
it's the size difference that does the magic.

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ricardobeat
"Specifically, glass is placed in a 400°C molten potassium salt bath, which
forces potassium ions to replace the sodium ions originally in the glass. The
larger potassium ions take up more space between the other atoms in the glass.
As the glass cools, the crunched-together atoms produce a high level of
compressive stress in the glass that helps protect the surface from mechanical
damage."

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jspiros
I remember learning about these many years ago, and just thought of them as a
simple novelty. Now that I'm looking at them again, I can't help but wonder if
these could be, or have been, weaponized? Seems like explosive glass would be
pretty harmful, and their behavior is akin to a "glass grenade".

More of a historical question, since there's clearly no obvious demand for a
weapon that requires the ability to produce glass in a world where chemical
explosives are comparatively easy to obtain. But, I'm sure there are places
and times in history where glass manufacture was practiced and the knowledge
of and ability to obtain chemical explosives was more limited.

Or, I suppose it might not be that dangerous. My understanding of "safety
glass" is that by being tempered, it also utilizes internal stresses similarly
to both strengthen the glass and ensure that, if broken, it breaks into
smaller less harmful pieces rather than large sharp shards. So, I suppose it
might make sense if it didn't cause that much harm, and was more like throwing
sand at someone...

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pyre
Watching the Smarter Every Day video linked in a couple of other threads, it
seems 'harmless.' The guy shatters it in his hand with nothing other than
safety goggles on.

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jvdh
Funny, these things are often seen hanging in pairs in Dutch household
windows. I never thought there was anything peculiar about these things.

Mind you, these kind of drops are more stylized straight versions, so I'm not
sure if they do have the same properties.

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jere
Wow, this is interesting. I love how it was used as a party trick for
centuries. I could see this being used in a sci fi story to great effect.

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youthforever
Drop

