You may have seen this.

Thermite is not an explosive, but it can do a very good impression of one if there's water in the area. Or ice.

Pykrete would no doubt have held up better

(Oh, and do try to ignore the YouTube commenters and their d00d-this-is-what-s4ddam-used-to-bring-down-the-WTC theories.)

The clip's from a German show called "Clever!", which has its own video page here.

Any time I see a big-boom TV-show science demonstration these days I can't help but suspect it was faked, thanks to the scumbags at Brainiac, but this one does seem to be genuine.

I mean, forget water. Thermite will explosively boil zinc.

The bit at the end of that video is quite a bad idea if you're not wearing eye protection. And I'd keep my mouth shut, too. Violently heating any stone-like material can result in steam pockets inside it firing chips of hot rock at you at considerable speed.

While we're on a roll, I feel the need for a traditional pyro video, with shaky camerawork and autofocus hunting all over the place while a small thing glows in the middle of the frame.

That's pretty good. But it doesn't have a bunch of whooping drunks.

Ah, there you go.

There's a whole class of thermite reactions. The iron oxide and aluminium one is just cheap and powerful.

Here, for instance, is copper oxide and zinc:

The pros ignite their thermite with super-sparklers made for the purpose, which are easier to light than magnesium ribbon, fatter and hotter than standard sparklers, and very hard to extinguish.

These last two videos are from more Germans, this time netexperimente.de, whose YouTube profile page is here. There's a decent collection of other whooshes, oozes and bangs there, including a simple demonstration of the classic dust explosion (it's noisier if you jam the lid on harder...) that Adam and Jamie failed to perform back in '04. There are plenty of other classics, too, including a nice version of sugar and sulfuric acid - in which, essentially, the concentrated acid is so thirsty for water that it pulls it right out of the sucrose molecules, leaving a frothy mass of black carbon.

(If you're wondering what the deal is with the "burning snowball", it's a methane hydrate ball.)

And here's someone melting through a rock with a thermal lance...

...and then burning some pennies. As you do.

Modern US one cent coins are copper plated zinc, and zinc burns quite well if you get it hot enough.

If you inhale much of the zinc oxide smoke, though, you'll get ill. "Metal fume fever" has influenza-like symptoms, and zinc fumes are the most common cause (welders, who get it when they breathe the smoke while welding galvanised steel, call it "zinc flu"). It probably won't kill you, but it might.

3 Responses to “Exothermia”

  1. matt Says:

    I don't even have a TV any more, but back when I did, "Clever" was one of the few shows I enjoyed. Celebrities on the show are asked a series of science-based questions, with multiple-choice answers, and the presenter you see in the video then explains the science behind the answers in a fun sort of way. It's fun because you get to try to work out the answer yourself, and because the phenomena that they show are usually of a quite unintuitive sort. I have a strong science background, but still probably only got about half the questions right.

    I gather that Brainiac is similar, so it's kind of a shock to see the results being faked there. I'd never even considered Clever being faked, but I guess it just goes to show that you have to be skeptical about everything you see and hear...

  2. Daniel Rutter Says:

    Brainiac is not similar. I watched it a few times, and just couldn't stand it; most of the time they're obviously just doing a stunt that proves and/or demonstrates nothing, while the voice-over bullshits in a sciencey way. I got sick of shouting at the TV long before I learned that they just plain faked it when honest stuff didn't look cool enough.

    Mythbusters often get stuff wrong, and also blow shit up just for fun, but they make a serious effort to get stuff right, and never (seem to) pretend they're doing something that they aren't.

  3. boredblogtrawler Says:

    Yeah, I've seen a thermal lance used underwater to cut through 4.5" of steel (a chain link). It took less than 10 minutes and was quite an impressive display, even through the helmet cam that was capturing the image I saw. I can definitely see the appeal of playing with one!

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