For as long as I can remember, I've loved gunpowder. One of my fondest childhood memories is pulling down volume G of the encyclopedia and seeing the formula for this magic substance for the first time. Saltpeter, sulfur and charcoal, listed with exact percentages! That was heady stuff for a kid who had been forced to rely on collecting match heads for flammable material. But where to get the ingredients? I settled on hitting up pharmacists, telling one that my mom had sent me out to get saltpeter for canning, and a different one that she'd sent me out for sulfur and I didn't know why (because I couldn't think of a better cover story).
What I didn't know is that all the ingredients for gunpowder are readily available side by side, no questions asked, in any garden center or home-improvement store. Charcoal is sold for grilling, and sulfur comes in bags that say "sulfur" in big letters (nice old ladies use it for dusting roses). But the key secret I never figured out back then is that most brands of stump remover are little more than pure saltpeter.
To make real gunpowder that actually goes bang, these ingredients must be ground together in a ball mill or stone rolling mill for hours, during which time there is a good chance that the powder will explode prematurely. (Seriously, don't try this at home unless you have the correct type of remotely operated mill.) Instead, I always ground the ingredients separately with a mortar and pestle and then mixed them gently without further grinding. This results in a powder that burns energetically but slowly: perfect, it turns out, for making sparkler cones. (Check out our video of fireworks in ultra slow motion here.)
I never got hurt, and with the kind of gunpowder I was making, common sense was enough to keep me in one piece. That wasn't the case for everything I used to experiment with, though. Sometimes I cringe when I think about all the times I was lucky not to blow my head off.
WARNING! Creating and igniting pyrotechnic mixtures of any kind, including gunpowder, is inherently dangerous and is illegal in some places. Harmless experimentation, especially by kids, can be taken very seriously by the authorities, so an adult must always be present and take full responsibility