July 4th handicrafts

'Tis the season for my ancient sparkler-bombs page to suddenly get a lot more traffic, as the great American combination of patriotism, capitalism and pyromania reaches its annual peak.

If you're wondering what sort of bomb we're talking about here, this video should fill you in. It was grabbed from elderly videotape by my friend Mark. Note the commentary and a brief ceiling-scorching appearance from a person who somewhat resembles me, but is much younger and thinner and has an annoying reedy voice.

(WD-40 cans don't do that any more. They probably still do if you put a little pile of thermite on top of them, though. This concludes the Extremely Dangerous Suggestions portion of this blog post.)

So, on the subject of Sparkler "Bombs" That Do Not Actually Go Bang, here's a letter I got a while ago:

I am considering building a sparkler "bomb" for the upcoming July 4th holiday here in the US. In the course of my research on how to safely construct one, I came across some other pages stating that sparklers without magnesium were substandard and would not produce the desired effect. These pages were directions for actual enclosed bombs but I was wondering if you had tried the magnesium-less sparklers in the course of your experimentation for the "fwoosh" version and whether there was a noticeable difference if you had.

The reason why I am asking is because the only sparklers I can find around here that are made with wire do not have magnesium and the ones that do are on wooden sticks.


My answer:

I think most of the combustion energy of a sparkler comes from the oxidiser-fuel combination - generally something like potassium nitrate plus dextrin, with optional extra carbon, sulfur, sawdust or whatever. The stuff that makes the actual sparks contributes relatively little to the combustion.

The spark composition obviously does contribute a lot to the great vertical whoosh of sparks you get from the standard, safe sparkler "bomb", though, so it's possible that less-sparky sparklers will make much the same noise, and much the same amount of heat, but be rather less exciting to watch.

(I've never tried wood-stick sparklers for this job either. They might work OK, if bound together with coat-hanger wire or something, but I don't know.)

It's tempting to spice up the combustion with, say, a dollop of aluminium powder such as you can buy from some paint suppliers. This might actually work well, but note that flammable metal powders can "self-confine", in which the metal chaotically melts even as it burns, causing small-to-medium explosions. That sort of thing could make a sparkler bomb significantly less safe.

Honestly, I think any sparkler that sparks reasonably well, even if it's a bit less impressive than the classic bright-white-sparks aluminium/magnesium type, should work. It's easy enough to do a small-scale test, though; make a mini-bomb of only 100-odd sparklers, and see what it does. It'll burn much slower than a bigger bomb (a full-sized sparkler bomb has a burn time of only about one second), but should still demonstrate the principle.

4 Responses to “July 4th handicrafts”

  1. Arvid Says:

    My experience is that wood stick sparklers don't really do well. The metal wires in a regular bomb actually seem to retard the reaction. Our wood stick sparkler bomb with about ~1000 sparklers burned so fast it looked more like a camera flash. It didn't woosh, it just evaporated.

  2. Fallingwater Says:

    I wish I could get sparklers in large amounts here in Italy. The most I've seen in one pack is 30, and they commonly cost some €2-3 each pack :(

  3. davolfman Says:

    As for your comment on using sparklers to start thermite: according to my dad (who finger-of-god'ed a rural mailbox once in his youth) magnesium (powder probably best) also works for starting it. I take a great deal of comfort in learning what happens when you do all these dangerous things without having to do them myself. My question about the sparkler ingredients would be if the ion(izer?) is trading metals like in a thermite reaction, or if it's more of a traditional case like nitrates going boom or powdered metals catching fire.

  4. Fallingwater Says:

    I've just happened upon this link which seems very relevant. I move for all fireworks to always be detonated close to the ground, and damn the consequences - that was just too pretty to look at. :D

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