Wiktionary
n. (context dated photography English) A powder that burns with a very rapid flash when ignited; used in early flash photography
Wikipedia
Flash powder is a pyrotechnic composition, a mixture of oxidizer and metallic fuel, which burns quickly and if confined produces a loud report. It is widely used in theatrical pyrotechnics and fireworks (namely salutes, e.g., cherry bombs, M-80s, firecrackers, and cap gun shots) and was once used for flashes in photography.
Different varieties of flash powder are made from different compositions; most common are potassium perchlorate and aluminium powder. Sometimes, sulphur is included in the mixture to increase the sensitivity. Early formulations used potassium chlorate instead of potassium perchlorate.
Flash powder compositions are also used in military pyrotechnics when production of large amount of noise, light, or infrared radiation is required, e.g. missile decoy flares and stun grenades.
Usage examples of "flash powder".
I began to lay down the flash powder, trying to do it without her noticing.
Fitzfarris immediately began canvassing the Apotheken of the city until he found one that stocked the lycopodium flash powder, so he could add his vanishing-girl fillip to the occasion.
I guess they were right about that flash powder causing the fire in the first place .
I said, reaching into my belt pouch for a pinch of magikal flash powder to cover up the fact that I was going to use our D-hopper.
Kate inspected a sheaf of photographs on her rolltop desk, all the same size, all taken by the same camera and bright with flash powder.
Marcus took several close shots of the prints, the burst of the flash powder illuminating the whole roof area but quickly dissipating in the blackness out over the harbor.
I let drop the sheet of invisibility and simultaneously ignited the bag of flash powder.
In his left hand was a quantity of ordinary flash powder, such as photographers use.
So none could see, he poured out a little pile of the flash powder.
Other lights came from moving pylons, five feet tall, that shot up mini-rockets filled with flash powder and confetti and ticker tape, in addition to beams that swung back and forth like searchlights at a world premiere.