Something explosive?

Do you know of a chemical I can put on metal "stage" weapons that will make a crack, pop, spark, or bang upon impact? I'm afraid to google anything about it because I'll probably use a bunch of keywords that are wrong and then get arrested.

I'm doing costumes and props for some weird improv thing for a theater troupe, and it's crunch time.

>>5

I think that really depends on how big you want the sparks to be.  A higher voltage source would produce actual arcing (think along the lines of a Jacob's Ladder) when the swords are obviously not touching (which would seem distracting and unrealistic to me).  No matter what though, I'd try to use something with a lower current, but a higher voltage (a 9V battery or two, connected in series, with a step-up transformer, so it'd be the equivalent of a stun-gun).