Prince Rupert's Drop EXPLODING in Epoxy Resin at 456,522 fps - Smarter Every Day 273

Destin: That one lived. Here at Orbix Hot Glass, they're masters at creating beautiful works of art using the properties of glass. When glass heats up, it expands. And when it cools down, it contracts. And it was here that I first learned about the Mystery of the Prince Rupert's Drop. We made Prince Rupert's drops by dripping molten glass down into cool water. And when the glass hit the water, it froze. It hardened up. And then it started to contract because it was cooling down. The inside, however, was still molten. So as it started to cool, it pulled in on that outside shell, which was already hard.

This is a Prince Rupert's Drop; the outside is in an extremely high compressive stress, and it's very tough. But the inside is in extremely high tensile stress. The mystery of the Prince Rupert's Drop, though, is how tough they are. If you hit the outside with a hammer, it WON'T break. But if you even nick the tail, it will explode, not shatter. It will actually explode. That's why these things are so interesting. They're even tougher than I first imagined, though, because I've done several other experiments where I actually shoot bullets at Prince Rupert's Drops, and they shatter the bullet. And it's not until the tail wiggles that the whole thing will explode.

Today, we want to understand this explosion. We want to see if we can characterize the spatial fragment distribution of the glass as it flies away as this thing explodes. (Destin's Voice Echoing in cardboard box) All right. I was successful in my attempts to transport the Prince Rupert's Drops here to the house. Trent's with me today because we have two high-speed cameras to run.

Trent: Wassup!

We're going to run this one right here, it's called a 7510. It runs very fast. This is the Smarter Every Day 2511 that'll do 25,000 frames per second at 720p. So here's what we're going to do; I got to reading the paper, it's "Micrographa" by Robert Hooke. I was a little bit wrong. He didn't actually suspend the drop in resin. He actually used this stuff. It's called ICTY-UH-Cola, I believe (probably wrong), but it's a really fancy glue made out of fish bladders. That's interesting. And the way he did it, he kind of like coated the Prince Rupert's Drop and then wrapped it in leather and then popped it, and that helped it retain its shape when it exploded so he could see what happened.

That's not what I want to do, though. I want to do something different. We've got these plexiglass boxes here. I want to fill it with an epoxy. This is a two-part epoxy used for furniture stuff, coating wood and things like that. It's a one-to-one mixture. So we're going to mix this in here. We're going to use this fancy Mix-o-tronic 3000™ (laughs). We're going to mix that stuff in one of these cups and then we're going to degas it. And the purpose of doing this is to get all the bubbles out of it.

And then I'm going to start a stopwatch here. And what I'd like to do is I would like to get the hardness of the resin to be just perfect enough where when we crack the Prince Rupert's Drop, you can see the fragmentation, the explodey-ness of the Prince Rupert's Drop. You'll notice that we have this angle which shows like the overall propagation of the fracture wave as it goes down the length of the Prince Rupert's Drop. So the one high-speed camera I'd like to capture that. But the other one, I would like to get it nose on like this because I want to see the explosion out in this radial direction. So I think we prepare the epoxy, we start the stopwatch, we know how long the epoxy is hardening, and then I will suspend it.

We'll get aligned, and then I'll pop it, and then we'll get the high speed and see what goes down. You cool with that?

Trent:

OK, cool. So that's step one, and then we'll do it at some duration of time that represents a certain hardness factor. And then we'll interpolate between there and see if we can get the right amount of time.

Oh man, this feels like a thing... <♬ Music Starts ♬> <"Cicada's Waltz" by A Shell In The Pit> I need gloves, don't I? This makes me so happy, dude. Oh, I got a lot of air in that Mix-a-Tronic 6000. Starting the clock! Boop! Analog for the win. Oh! A BUG went in there! This is how Jurassic Park happens.

Oh, man, it's not what we want. Get out of there, bug! All right, that pen's done. It's warm already. We're going to pull the... <a lot going on, thinking slows down> pull the bubbles out of that. Let's get a camera over here and see what's going on. It's gonna boil. There she goes!! Getting all the air out of it so we can see into it. That's a lot of air. I don't think I Mix-A-Tronic'd 6000 very good.

All right. I think when we let pressure back in all the bubbles will get small. All right. Reapplying atmospheric pressure... oh, the bubbles are getting small. It's getting clear.... It's got streaks in that you can see the heat. You can't really see.... it's kind of cloudy. It's not crazy warm.

Trent: You might need to mix it some more.

Destin: Mix it some more? This is the manual Mix-a-Tronic 2000; it's getting clear. I want to put more vacuum on that... Turning it off.... OK. Yeah, that's crazy. If I mix it by hand, it gets cleaner. OK. And we did end up with some bugs in there. Jurassic Park style. Oh, it's smokin'!!!! (Clearly excited and perplexed) It.... It's Smokin! You see this!?

Trent: Oh, I do see... It's su...moking! Exothermic to the max! All right, here we go. Getting the Leatherman... I'm kind of scared of the Prince Rupert's Drop. Your goggles are on? All my goggles are on. I'm going to position the bulb towards you. Oh, it's getting hard.

Trent: Oh, man. What happened?

Destin: I got, like, a hard layer. Oh, it's getting hard. FAST.

Trent: Close your mouth.

Destin: Oh, yeah! Good point! D: Ready?

Trent: Ready.. Three, two, one. <CRACK!> OK, trigger... Whoa! My mouth was open a little bit. OK.... Fragmentation did not move a lot, so that actually solidified too hard. It was at 23 minutes since the moment the Mix-A-Tronic touched it.

Let's see what we have here. Yeah. So we didn't get a lot of movement there. Didn't get a lot of movement at all. You can see that the Prince Rupert's Drop solidified in kind of a weird way. NOT what I was going for. Less than ideal results...

Um, let's go see what is on the high-speed cameras. That's fast. All right, so playing through out of focus a little bit, that's cool. So you can see it run. The racetrack, right? OK, so look. At the fragment distribution up top. You can see that. It's spreading out, but the down below, we kind of overexposed a little bit. But the epoxy is impeding the explosion, so it's not going out. We have to science harder. You can always get what you want... but if you try, sometimes you'll get what you need. (giggles) Look at that. When I was putting it in, there, I hit that floor. I couldn't go below that. So we're not solidifying at the same rate across.

So I think we need to insert the Prince Rupert drop earlier. Yes. And what this also means is we may end up with a... an asymmetric fragmentation distribution because the viscosity might not be homogeneous.

Trent: Yes.

Destin: OK.

Trent: Whatcha doing there?

Oh, you know... just trying to mix the vertical strata as well as the horizontal. I remember my baseball coach on a camping trip taught me that mixing eggs is better with a fork than a spoon.

We're pretty goopy this time. Smoking's happened. OK, I'm going to try in three.... two... one. Trying..... Don't trigger yet. Here we go. And..... <BANG!> Ouch! Oh, it's hot. Oh, man. It got on my finger and it sunk.

Trent: You alright?

Destin: Yeah, I'm good. It's the epoxy was hotter than I expected. OK, I'm going to wash that off for a quick so I don't get burned with the epoxy on my watch. That was like, 18, 19 minutes, man. OK, this is hard. <You can hear the shards above the water differently than what's in the container> <The high-speed camera doesn't record sound>

The fluid is too liquid. We might not be able to do this because it didn't dissipate a crazy amount, and then it fell down, so this might not be possible. So there's definitely a shockwave. This shockwave propagates right into the bulb, right am I seeing that right? Like there's some kind of momentum to the shockwave.

Oh, we learned something. OK, so there's a shockwave that just goes along the axis of the bulb boom. And then afterwards, the fragmentation. OK, so a pressure wave hits the glass; that's cavitation, I assume, on the glass.

Trent: So right there is when it gets the biggest and then it starts to slam back shut.

Destin: It sure does.

Trent: Hydrostatic pressure of the fluid, right?

Destin: I would think so. How can we make that shot better?

You're asking the right questions. So we need to get a shot between that viscosity and the first shot to viscosity.

Trent: Yes.

Destin: So it's like right after it starts smoking.

Trent: Well, we know.

Destin: Yeah. It's like we wait for the potion to get ready. It starts smoking. <We're like, all right, <Pumps, valves, liquids... the sounds of general awesomeness>

Trent: I see smoke.

Destin: You see magic smoke?

Trent: I see magic smoke.

Destin: Magic smoke tiiiiiime! We need to wait 2 minutes for magic smoke time to take effect. It's gelatinous.

OK, ready? Yep. Three, two, one. Do it, Destin!

Trent: Keep it centered!