Re: Pyrotechnics

Anders Sandberg (
Wed, 25 Dec 1996 01:43:10 +0100 (MET)

On Tue, 24 Dec 1996, James Rogers wrote:

> >(Being a cautious person, I dislike experiments that are intended to go
> >BOOM. But I'm still proud of my utterly insane magnesium-manganese
> >dioxide-potassium chlorate mixture)
> >
> Although a magnesium/manganese dioxide/potassium chlorate mixture doesn't
> have any explosive properties, it is *very* exothermic. Thermite+.
> Definitely a lot of fun.

Actually, it was seriously explosive. An enclosed spoonful or so (I don't
know the exact amount since a friend with a death wish did the actual
mixing) was enough to blow a coconut and a silly hat into oblivion, and
leave a one meter wide crater in packed soil.

> I assume the potassium chlorate was to make ignition easier? I certainly
> commend you on your choice of manganese dioxide. Not the most commonly used
> metal oxide, but definitely the best for this application. Net thermal
> output is 25-35% higher than iron oxides.

Well, the idea was to use the catalytic reaction between the manganese
dioxide and the chlorate that releases oxygen; I guessed it would make
the otherwise strong magnesium-chlorate reaction stronger. In retrospect,
I doubt that was the real reaction, but the combination was definitely
powerful. And it made me nervous, I have never liked chlorates...

> 1) Replace magnesium with aluminum. A little harder to ignite, but it
> significantly boosts the thermal output.

One fun experiment we did (it was a young scientist association in
southern Stockholm) was to make thermite using copper oxides. It managed
to vaporize coke cans quite nicely.

> 2) Replace potassium chlorate with sulfur. Aluminum/Sulfur mixtures make
> good high-temp sub-igniters and have better thermal characteristics than
> potassium chlorate/magnesium mixtures. It is also more stable.

The residue also reacts with water to form hydrogen sulfide, which may or
may not be a fun side effect.

Ah, the reckless days of highschool. I still remember when one experiment
blew up, set fire to a small field of grass and rained metal pieces over a
large area. The police arrived, only to find a group of youngsters in
white lab coats carrying electric gear and gas masks (another of my
less-than-safe inventions: yellow cadmium fog) arguing about how much zinc
there ought to have been in the mixture. They just looked pained when we
started to explain :-)

Anders Sandberg Towards Ascension!
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y