Flash powder

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.

Normally, flash powder mixtures are compounded to achieve a particular purpose. These mixtures range from extremely fast-burning mixtures designed to produce a maximum audio report, to mixtures designed to burn slowly and provide large amounts of illumination, to mixtures that were formerly used in photography.

Because of the above-mentioned instability, the combination of aluminium powder and potassium chlorate is a poor choice for flash powder that is to be stored for more than a very short period of time. For that reason, it has been largely replaced by the potassium perchlorate mixtures. Chlorate mixes are used when cost is the overriding concern because potassium chlorate is less expensive than perchlorate. It is critically important to exclude sulphur and any acidic components from these mixtures. Sometimes a few percent of bicarbonate buffer is added to the mixture to ensure the absence of acidic impurities.

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