Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet (2023) | Hacker News Reader

Why 'Prince Rupert's Drop' Glass Is Strong Enough to Shatter a Bullet (2023)

popularmechanics.com

63 pointssusam31 comments

There's a pretty amazing video here showing a Prince Rupert's drop defeaing a hydraulic press: https://www.youtube.com/shorts/ns7PQjjqHIo

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.

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.

[1] https://www.youtube.com/watch?v=4SuPFbeqqKU

[2] https://www.youtube.com/watch?v=A6NUNroyUys

Slowed down: https://youtu.be/tRUngxK2yXY

You can see the steel deforming - definitely soft steel.

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 ^^;

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.

youtube says the mythbusters video is from 10 years ago so it was written sometime since then.

And according to Wikipedia [1] the first commercial use of Gorilla Glass was the original iPhone in 2007, even if the name was officially coined in 2008

[1] https://en.m.wikipedia.org/wiki/Gorilla_Glass

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

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.

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.

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.

The best part is if you melt away the weak tail, all you’re left with is the strong bulb.

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?

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.),

Is glass still considered a form of liquid? Think I remember reading something about that years ago.

No, that's a classic misconception. People claimed that windows "flowed" because really old ones were thicker at the bottom, but that was just how some old window glass was made.

I think the basis of the claim is that glass doesn't have the same kind of phase transition that a crystalline solid would. It just sort of gradually becomes more liquid-like as you heat it.

Yeah if you’re installing an uneven pane where would you orient the thick side?

The bottom.

No, its disordered (ie. not a crystal) but not a liquid, it won't flow like a viscous liquid.

My comment was a bit over simplified, they do flow, but the time scale exceeds the entirety of human history [1].

[1] https://doi.org/10.1119/1.19026

Similar to the misconception that Earth's mantle is liquid. It isn't, but time is deep enough for solid rock to flow.

My first thought was to see it under hydraulic press and the internet delivered.

What it takes to actually destroy it (by applying pressure at a wrong point)?

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.

Sure, but I am asking about applying pressure to the head.

Someone needs to invent a way to make tank armor out of Prince Rupert's Drop glass.

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?

They must have gotten the librarian in the video from Central Casting.

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