Flash Powder
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Flash powder is a
pyrotechnic composition A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic s ...
, a mixture of
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
and metallic fuel, which burns quickly and produces a loud noise regardless of confinement. It is widely used in theatrical pyrotechnics and
fireworks Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices ...
(namely
salutes A salute is usually a formal hand gesture or other action used to display respect in military situations. Salutes are primarily associated with the military and law enforcement, but many civilian organizations, such as Girl Guides, Boy Sco ...
, e.g.,
cherry bomb A cherry bomb (also known as a globe salute or kraft salute) is an approximately spherical exploding firework, roughly resembling a cherry in size and shape (with the fuse resembling the cherry's stem). Cherry bombs range in size from in diamet ...
s, M-80s,
firecracker A firecracker (cracker, noise maker, banger) is a small explosive device primarily designed to produce a large amount of noise, especially in the form of a loud bang, usually for celebration or entertainment; any visual effect is incidental t ...
s, and
cap gun A cap gun, cap pistol, or cap rifle is a toy gun that creates a loud sound simulating a gunshot and smoke when a small percussion cap is ignited. Cap guns were originally made of cast iron, but after World War II were made of zinc alloy, and mo ...
shots) and was once used for
flash Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...
es in
photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed ...
. Different varieties of flash powder are made from different compositions; most common are potassium perchlorate and
aluminium powder Aluminium powder is powdered aluminium. This was originally produced by mechanical means using a stamp mill to create flakes. Subsequently, a process of spraying molten aluminium to create a powder of droplets was developed by E. J. Hall in the ...
. Sometimes,
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
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 grenade A stun grenade, also known as a flash grenade, flashbang, thunderflash, or sound bomb, is a less-lethal explosive device used to temporarily disorient an enemy's senses. Upon detonation, they produce a blinding flash of light and an extremely lo ...
s.


History

Lycopodium powder Lycopodium powder is a yellow-tan dust-like powder, consisting of the dry spores of clubmoss plants, or various fern relatives. When it is mixed with air, the spores are highly flammable and are used to create dust explosions as theatrical spec ...
is a yellow-tan dust-like powder historically used as a flash powder. 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 Magic or Magick most commonly refers to: * Magic (supernatural), beliefs and actions employed to influence supernatural beings and forces * Ceremonial magic, encompasses a wide variety of rituals of magic * Magical thinking, the belief that unrela ...
acts and for
cinema Cinema may refer to: Film * Cinematography, the art of motion-picture photography * Film or movie, a series of still images that create the illusion of a moving image ** Film industry, the technological and commercial institutions of filmmaking ...
and
theatrical Theatre or theater is a collaborative form of performing art that uses live performers, usually actor, actors or actresses, to present the experience of a real or imagined event before a live audience in a specific place, often a stage. The p ...
special effects Special effects (often abbreviated as SFX, F/X or simply FX) are illusions or visual tricks used in the theatre, film, television, video game, amusement park and simulator industries to simulate the imagined events in a story or virtual wo ...
.


Mixtures

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.


Aluminium and chlorate

The combination of
aluminium powder Aluminium powder is powdered aluminium. This was originally produced by mechanical means using a stamp mill to create flakes. Subsequently, a process of spraying molten aluminium to create a powder of droplets was developed by E. J. Hall in the ...
and potassium chlorate is unstable, and a poor choice for flash powder that is to be stored for more than a very short period. For that reason, it has been largely replaced by the potassium perchlorate mixtures. Chlorate mixes are still used when cost is the overriding concern because potassium chlorate is less expensive than perchlorate. The simplest is a two-component chlorate mix, although this is rarely used. :KClO3 + 2Al → Al2O3 + KCl The composition is approximately 70% KClO3 : 30% Al by weight for the reactants of the above stoichiometrically balanced equation. It is considered critically important to exclude sulfur and any acidic components from these mixtures. Sulfur oxidises and absorbs moisture to produce sulfuric and thionic acids; any acid in the mixture makes it unstable. Sometimes a few percent of bicarbonate or carbonate buffer is added to the mixture to ensure the absence of acidic impurities.
Sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
is deliberately added as a third component to this mixture in order to reduce the
activation energy In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules p ...
. 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.
Antimony trisulfide Antimony trisulfide (Sb2S3) is found in nature as the crystalline mineral stibnite and the amorphous red mineral (actually a mineraloid) metastibnite. It is manufactured for use in safety matches, military ammunition, explosives and fireworks. It ...
may be used as an alternative, and is more stable in storage.


Potassium nitrate, aluminium and sulfur

This composition, usually in a ratio of 5 parts potassium nitrate, to 3 parts aluminum powder, to 2 parts sulfur, is especially popular with hobbyists. It is not very quick-burning unless exceptionally fine ingredients are used. 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. Other ratios such as 6 KNO3/3 Al/2 S and 5 KNO3/2 Al/3 S also exist and work. All ratios have similar burn times and strength, although 5 KNO3/3 Al/2 S seems to be dominant. :2 KNO3 + 4 Al + S → K2S + N2 + 2 Al2O3 The composition is approximately 59% KNO3 : 31.6% Al : 9.4% S by weight for the reactants of the above
stoichiometric Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equ ...
ally balanced equation. For best results, "German Dark" aluminum should be used, with air float sulfur, and finely ball-milled pure potassium nitrate. The finished mixture should never be ball milled together.


Aluminium and perchlorate

Aluminium powder and potassium perchlorate are the only two components of the pyrotechnic industry standard flash powder. It provides a great balance of stability and power, and is the composition used in most commercial exploding fireworks. aka A B mixture The balanced equation for the reaction is: :3 KClO4 + 8 Al → 3 KCl + 4 Al2O3 The stoichiometric ratio is 34.2% aluminum and 65.8% perchlorate by mass. A ratio of seven parts potassium perchlorate to three parts dark pyro aluminium is the composition used by most pyrotechnicians. For best results, the aluminium powder should be "Dark Pyro" grade, with a flake particle shape, and a particle size of fewer than 10 micrometres. The KClO4 should be in powder form, free from clumps. It can be sieved through a screen, if necessary, to remove any clumps prior to use. The particle size of the perchlorate is not as critical as that of the aluminium component, as much less energy is required to decompose the KClO4 than is needed to melt the aluminium into the liquid state required for the reaction. Although this composition is fairly insensitive, it should be treated with care and respect. 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. One method of mixing flash is to put the components in the final device and handling the device will mix the flash powder. Paper/cardboard is chosen over other materials, such as plastic, as a result of its favorable
triboelectric The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rub ...
properties. Large quantities should never be mixed in a single batch. Large quantities are not only more difficult to handle safely, but they place innocent bystanders within the area 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. (Note: 3 grams of mixture is enough to explode in open air without constraint other than air pressure.) 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.


Magnesium and nitrate

Another flash composition common among amateurs consists of
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
powder and
potassium nitrate Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitr ...
. Other metal nitrates have been used, including barium and strontium nitrates. Compositions using nitrate and
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
metal have been used as photographic flash powders almost since the invention of photography. Potassium nitrate/magnesium flash powder should be mixed and used immediately and not stored due to its tendency of self-ignition. If magnesium isn't a very fine powder it can be passivated with linseed oil or potassium dichromate. The passivated magnesium flash powder is stable and safe to store. :2 KNO3 + 5 Mg → K2O + N2 + 5 MgO The composition is 62.5% KNO3 : 37.5% Mg by weight for the reactants of the above stoichiometrically balanced equation. Below is the same reaction but involving
barium nitrate Barium nitrate is the inorganic compound with the chemical formula Ba( NO3)2. It, like most barium salts, is colorless, toxic, and water-soluble. It burns with a green flame and is an oxidizer; the compound is commonly used in pyrotechnics. Man ...
. :Ba(NO3)2 + 5 Mg → BaO + N2 + 5 MgO Mixtures designed to make reports are substantially different from mixtures designed for illumination. A stoichiometric ratio of three parts KNO3 to two parts Mg is close to ideal and provides the most rapid burn. The magnesium powder should be smaller than 200 mesh, though up to 100 mesh will work. The potassium nitrate should be impalpable dust. This mixture is popular in amateur pyrotechnics because it is insensitive and relatively safe as such things go. For photographic use, mixtures containing magnesium and nitrates are made much more fuel rich. The excess magnesium is volatilized by the reaction and burns in air providing additional light. In addition, the higher concentration of fuel results in a slower burn, providing more of a "poof" and less of a "bang" when ignited. A formula from 1917 specifies 5 parts of magnesium to 6 parts of
barium nitrate Barium nitrate is the inorganic compound with the chemical formula Ba( NO3)2. It, like most barium salts, is colorless, toxic, and water-soluble. It burns with a green flame and is an oxidizer; the compound is commonly used in pyrotechnics. Man ...
for a stoichiometry of nine parts fuel to one part oxidizer.Watkins, ''The Photographic Journal of America'', Vol. 54, 1917, Philadelphia, p. 384 Modern recreations of photographic flash powders may avoid the use of barium salts because of their toxic nature. A mixture of five parts 80 mesh magnesium to one part of potassium nitrate provides a good white flash without being too violent. Fuel rich flash powders are also used in theatrical
flash pot Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
s. Magnesium based compositions degrade over long periods, meaning the metallic Mg will slowly react with atmospheric oxygen and moisture. In military pyrotechnics involving magnesium fuels, external oxygen can be excluded by using hermetically sealed canisters. Commercial photographic flash powders are sold as two-part mixtures, to be combined immediately before use.


Magnesium and PTFE

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. These flares are used as decoys from aircraft that might be subject to heat-seeking missile fire. :2n Mg + (C2F4))n → 2n MgF2 (s) + 2n C (s)


Antimony trisulfide and chlorate

This mixture, and similar mixtures sometimes containing pyro aluminium have been used since the early 1900s for small "Black Cat" style paper
firecracker A firecracker (cracker, noise maker, banger) is a small explosive device primarily designed to produce a large amount of noise, especially in the form of a loud bang, usually for celebration or entertainment; any visual effect is incidental t ...
s. Its extremely low cost makes it popular among manufacturers of low-grade fireworks in China. Like all mixtures containing chlorates, it is extremely sensitive to friction, impact and ESD, and is considered unsafe in pyrotechnic devices that contain more than a few tens of milligrams of the mixture. :3 KClO3 + Sb2S3 → Sb2O3 + 3 SO2 + 3 KCl This mixture is not highly energetic, and in at least some parts of the United States,
firecracker A firecracker (cracker, noise maker, banger) is a small explosive device primarily designed to produce a large amount of noise, especially in the form of a loud bang, usually for celebration or entertainment; any visual effect is incidental t ...
s containing 50 mg or less of this mixture are legal as consumer fireworks.


Safety and handling

Flash powders even within intended usages often release explosive force of deadly capacity. Nearly all widely used flash powder mixtures are sensitive to shock, friction and electrostatic discharge. In certain mixtures, it is not uncommon for this sensitivity to spontaneously change over time, or due to change in the environment, or to other unknowable factors in either the original manufacturing or in real-world storage. Additionally, accidental contaminants such as strong acids or sulfur compounds can sensitise them even more. Because flash powder mixtures are so easy to initiate, there is potentially a high risk of accidental explosions which can inflict severe blast/fragmentation injuries, e.g. blindness, explosive amputation, permanent maiming, or disfigurement. Fatalities have occurred. The various flash powder compositions should therefore not be handled by anyone who is unfamiliar with their properties, or the handling techniques required to maintain safety. Flash powder and flash powder devices pose exceptionally high risks to children, who typically cannot understand the danger and may be less adept with safe handling techniques. As a result, children tend to suffer more severe injuries than adults. Flash powders—especially those that use chlorate—are often highly sensitive to friction, heat/flame and static electricity. A spark of as little as 0.1–10 millijoules can set off certain mixtures. Certain formulations prominent in the
underground press The terms underground press or clandestine press refer to periodicals and publications that are produced without official approval, illegally or against the wishes of a dominant (governmental, religious, or institutional) group. In specific rec ...
contain both
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
and potassium chlorate. These mixtures are especially shock and friction sensitive and in many applications should be considered unpredictable. Modern pyrotechnic practices call for never using sulfur in a mix containing chlorate salts. Some flash powder formulations (those that use single-digit micrometre flake aluminium powder or fine magnesium powder as their fuel) can self-confine and explode in small quantities. 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. This is referred to as 'inertial confinement', and it is not to be confused with a detonation. Flash powder of any formulation should not be mixed in large quantities by amateur pyrotechnicians. Beginners should start with sub-gram quantities, and refrain from making large devices. Flash powder should only be made at the site at which it will be used. Additionally, the mixture should be made immediately before use. 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.


See also

*
Pyrotechnic initiator In pyrotechnics, a pyrotechnic initiator (also initiator or igniter) is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. T ...
*
Sprengel explosive Sprengel explosives are a generic class of materials invented by Hermann Sprengel in the 1870s. They consist of stoichiometric mixtures of strong oxidisers and reactive fuels, mixed just prior to use in order to enhance safety. Either the oxidiser ...
*
Thermite Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brie ...
* Black powder *
Lycopodium powder Lycopodium powder is a yellow-tan dust-like powder, consisting of the dry spores of clubmoss plants, or various fern relatives. When it is mixed with air, the spores are highly flammable and are used to create dust explosions as theatrical spec ...


References

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