Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet (2023)
31 comments
·April 9, 2025aragonite
dzdt
Yeah its not really what it looks like though. They put cylinders of soft metal in place of where you would expect the press to have hardened steel.
aragonite
Has this been confirmed? The original channel also posted a comparison video [1] showing what seems to be the same cylinders tested against titanium and tungsten cubes (though it's difficult to be sure they are identical)
There's also footage from another channel [2] showing a Prince Rupert's Drop bursting at 20 tons with significant damage to both the steel plate and the press.
KTibow
Slowed down: https://youtu.be/tRUngxK2yXY
philjohn
You can see the steel deforming - definitely soft steel.
darkwater
When was this article written? Last update is 2023 (so the title should at least reflect this) but down in the article talks about Gorilla glass by Corning as a novelty with possible future uses in smartphones.
Sent from a Gorilla glass smartphone with a corner almost broken ^^;
dragontamer
Prince Rupert's Drop is strong at compression but weak enough that your pinky finger can shatter it.
These 'hardness' stats are just marketing bullshit dressed up in barebones material science. They know most people haven't studied material science or understand what 'hardness' means.
test1235
video in lieu of the article's broken link:
Bullet vs Prince Rupert's Drop at 150,000 fps - Smarter Every Day 165: https://www.youtube.com/watch?v=24q80ReMyq0
HelloUsername
The article is also from 2023.
It's funny to see how topics on reddit (https://l.opnxng.com/r/Unexpected/comments/1jvhcme posted 2 days ago), 9gag (https://9gag.com/gag/aW4vpKd posted 1 day ago) and HN (posted today) are always connected.
mystraline
It reminds me of Cory docotorow's comment of something like 'there are 5 social media sites and everything is just copied from one another'
HN isn't immune either, given that karma provides 'rights to punish views and accounts' (downvoting). And it makes a great strategy to make a whole lot of socks with 520 karma, and selectively kill comments and stories you don't want.
actuallyalys
I’m sure sock puppets and voting rings play a role, but “this link was interesting to a bunch of people on sites with some overlap in interests and demographics” seems a simpler and better explanation.
qwerty456127
What it takes to actually destroy it (by applying pressure at a wrong point)?
ninkendo
A tiny amount of pressure applied to the “tail” of it shatters the whole thing instantly, that’s one of the coolest things about it.
undebuggable
My first thought was to see it under hydraulic press and the internet delivered.
ChrisMarshallNY
They must have gotten the librarian in the video from Central Casting.
dghughes
Someone needs to invent a way to make tank armor out of Prince Rupert's Drop glass.
undebuggable
Once I was stuck down a youtube rabbit hole of someone testing anti-tank portable launcher against increasingly thick ballistic glass. The conclusion was that no glass can resist anti-tank projectile. Maybe large enough Rupert's drop glass could?
dyauspitr
The best part is if you melt away the weak tail, all you’re left with is the strong bulb.
tifik
Would/does that actually work? Its been a while since I watched SED Destins video about it, so I dont remember if they experiment with that. But intuitively, heating the glass so non-uniformly that the tail would melt and the bulb remained solid enough to keep the internal stresses intact, wouldnt that steep temperature gradient within the crystaline structure cause the entire drop to break?
maxbond
In this video someone does it and it seems to work.
https://youtube.com/shorts/ERDmKW65t38
But it's a very small drop and they don't melt it all the way to the bulb. I imagine that it could shatter in some circumstances.
(Incidentally glass isn't a crystal, but that's just a nitpick.),
prox
Is glass still considered a form of liquid? Think I remember reading something about that years ago.
null
There's a pretty amazing video here showing a Prince Rupert's drop defeaing a hydraulic press: https://www.youtube.com/shorts/ns7PQjjqHIo