Flash powder is a mixture of oxidizer and metallic fuel which burns extremely quickly and if confined will produce a loud report. It is widely used in fireworks and theatrical pyrotechnics, and was once used for flashes in photography.

Different varieties of flash powder are made from different compositions; most common are potassium perchlorate and aluminum powder. Sometimes, sulfur is included in the mixture to increase the sensitivity.

Chemically, flash powder is highly unstable. It is a heat, static, friction, and impact sensitive explosive. It is considered to be one of the most volatile pyrotechnic compositions.

Flash powders, specifically chlorate/perchlorate ones, are unique in that they produce no gas products (all solid products), which means that they are not explosives by scientific definition. (Flash powder is however regulated as a high explosive in the United States by the Bureau of Alcohol, Tobacco, Firearms and Explosives). The loud report/explosion heard from salutes and M-80s is due to the near instantaneous rise in temperature and pressure within the container, which can exceed 400 times that of standard atmospheric pressure.

Production of flash powder

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Due to its instability, flash powder must be mixed in a fashion that minimizes friction and any possibility of static electricity. A standard black powder ball mill is completely unsuited for this purpose, due to the much greater sensitivity of flash powder. Hobbyist pyrotechnicians usually use a method called diapering, in which the materials are poured separately onto a large piece of paper, which is then folded up at the corners and gently rocked back and forth until the chemicals are thoroughly mixed. Professionally, automated systems are used to achieve the same result, and blast shields are usually in place in case of an explosion.

Aluminum and Chlorate

Aluminum powder and potassium chlorate is a very unstable recipe for flash powder, for that reason it has been largely replaced by the potassium perchlorate mixture. Aluminum powder and potassium chlorate is preferred only if cost is important, because potassium chlorate is less expensive than potassium perchlorate.

KClO₃ + 2Al --> Al₂O₃ + KCl

Aluminum and Perchlorate

Aluminum powder and Potassium Perchlorate make up the only 2 components of a popular and simple type of flash powder. This compound is relatively stable for a flash powder.

3KClO4 + 8Al --> 4Al2O3+ 3KCl

3 KClO4 : 8 Al

3(138.55) : 8(26.98)

415.65 : 215.84

Generally,70% potassium and 30% aluminum mass mix of potassium perchlorate and aluminum powder works very well. The more finely powdered the materials, the faster the reaction, and the "sharper" the flash.

Magnesium and Potassium Nitrate

Another method for the production of flashpowder is to use a 6:4 ratio of Potassium Nitrate to Magnesium. Be warned, this mixture is slightly more unstable than the aluminum mix.

6 parts Potassium Nitrate : 4 parts Magnesium

The finer ground (mesh) the magnesium is, the faster it will burn and the louder the bang (report)

External links

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• The Explosives and Weapons Forum contains a number of flash powder "recipes" using a wide variety of materials.
• Anarchy Blogging constantly updated, contains good flash powder information.

Explosives

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