Flash powder
From Wikipedia, the free encyclopedia
Flash powder is a mixture of oxidizer and metallic fuel which burns quickly and if confined will produce a loud report. It is widely used in theatrical pyrotechnics and fireworks (namely salutes, eg. cherry bombs, M-80s, and firecrackers), 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. Early formulations used potassium permanganate instead of perchlorate.
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. In that regard, they are similar to thermite mixtures.
Flash powder like mixtures are used in industry and aerospace for generation of large volumes of gas in gas generators, in pyrotechnic fasteners, and in other similar applications.
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[edit] Production 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.
[edit] Aluminum and Chlorate
Aluminum powder and potassium chlorate is a bad choice 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
[edit] 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 stable for a flash powder.
- 3 KClO4 + 8 Al → 4 Al2O3+ 3 KCl
- 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.
[edit] Magnesium and Potassium Nitrate
Another method for the production of flashpowder is to use a 3:2 ratio of potassium nitrate to magnesium.
- 3 parts Potassium Nitrate : 2 parts Magnesium
The finer ground (mesh) the magnesium is, the faster it will burn and the more smoke it will produce.
[edit] Boron and Potassium Nitrate
A mixture of boron and potassium nitrate is used by NASA as a gas generator and a rocket motor igniter. It is thermally stable, stable in vacuum, and its burn rate is independent on pressure.
[edit] Zirconium and Potassium Perchlorate
A mixture of metallic zirconium and potassium perchlorate, is known as NASA Standard Initiator. It yields rapid pressure rise, generates little gas but emits hot particles, is thermally stable, is stable under vacuum, and has long shelf life. It is sensitive to static electricity.
[edit] Manganese, Barium Chromate, and Lead Chromate
A mixture of manganese, barium chromate, and lead chromate is used as a time delay mix for pyrotechnic sequencing. It burns without production of gas.
[edit] External links
- The Explosives and Weapons Forum contains a number of flash powder "recipes" using a wide variety of materials.
