Flash powder
Flash powder is a pyrotechnic composition, a mixture of oxidizer and metallic fuel, which burns quickly (deflagrates) and produces a loud noise regardless of confinement.
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.
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.
[1] Today, the principal use of the powder is to create flashes or flames that are large and impressive but relatively easy to manage safely in magic acts and for cinema and theatrical special effects.
[2][3] However this gives the problem with acid production and instability and so these mixtures are generally considered too unstable to be stored and must be mixed immediately before use.
Although it incorporates sulfur, it is in fact fairly stable, sustaining multiple hits from a hammer onto a hard surface.
Adding 2% of its weight with boric acid is reputed to significantly increase stability and shelf life, through resistance to dampening through ambient humidity.
For best results, "German Dark" aluminum should be used, with air float sulfur, and finely ball milled pure potassium nitrate.
Hobbyist pyrotechnicians usually use a method called diapering, in which the materials are poured separately onto a large piece of paper, which is then alternately lifted at each corner to roll the composition over itself and mix the components.
Some amateur pyrotechnicians choose to mix the composition by shaking in a closed paper container, as this is much quicker and more effective than diapering.
Large quantities should never be mixed in a single batch, as they are difficult to handle safely and can put bystanders at risk.
In the event of accidental ignition, debris from a multiple-pound flash powder explosion can be thrown hundreds of feet with sufficient force to kill or injure.
No matter the quantity, care must always be taken to prevent any electrostatic discharge or friction during mixing or handling, as these may cause accidental ignition.
In addition, the higher concentration of fuel results in a slower burn, providing more of a "poof" and less of a "bang" when ignited.
Magnesium based compositions degrade over long periods, meaning the metallic Mg will slowly react with atmospheric oxygen and moisture.
A flash composition designed specifically to generate flares that are exceptionally bright in the infrared portion of the spectrum use a mixture of pyro-grade magnesium and powdered polytetrafluoroethylene.
This makes flash powder dangerous to handle, as it can cause severe hearing damage and amputation injury even when sitting in the open.
Self-confinement occurs when the mass of the pile provides sufficient inertia to allow high pressure to build within it as the mixture reacts.
When mixed, the transportation, storage, usage, various possession, and illegal "firearms" laws (including felonies) may come into effect that do not apply to the unmixed or pre-assembled components.
