ATF's Classification of Flash Powder

Selected Pyrotechnic Publications of K.L. and B.J. Kosanke Part 4 (1995 through 1997) This book contains 138 pages Stars Blown Blind ………………………………………………………………… P. 307-309. Fireworks and their Hazards ……………………………………………………… P. 310-320. Concussion Mortar Internal Pressure, Recoil and Overpressure as Functions of Powder Mass ………………………………………………………… P. 321-332. Hazardous Chemical Combinations ……………………………………………… P. 333-345. Explosive Limit of Armstrong’s Mixture ………………………………………… P. 346-347. Aerial Shell Drift Effects: A) The Effect of Long Mortars B) The Effect of Capsule-Shaped Shells ………………………………………… P. 348-352. Pyrotechnic Spark Generatiom: A Discussion …………………………………… P. 353-365. An Instrument for the Evaluation of Black Powder as a Propellant for Aerial Shells …………………………………………………………………… P. 366-379. Simple Measurements of Aerial Shell Performance ……………………………… P. 380-383. Flash Powder Output Testing: Weak Confinement ……………………………… P. 384-393. New Fast Fuse ……………………………………………………………………… P. 394-396. Burn Rates of Clusters of Gold Sparklers ………………………………………… P. 397-399. ATF’s Classification of Flash Powders …………………………………………… P. 400-401. A Survey of Concussion Powders ………………………………………………… P. 402-414. Sky Rocket Performance Characteristics ………………………………………… P. 415-417. Performance Comparison between Old and New Obron German Dark Aluminum …………………………………………………………. P. 418-419. Pyrotechnic Ignition and Propagation: A Review ……………………………… P. 420-431. Burn Rates of Clusters of Colored Sparklers …………………………………… P. 432-434. An earlier draft appeared in American Fireworks News, No. 160, 1995. Stars Blown Blind K. L. and B. J. Kosanke When an aerial shell bursts, stars that fail to burn are often said to be “blind stars”, or more descriptively as having been “blown blind”. This detracts from the beauty of the shell and contrib- utes to debris fallout. The problem can be caused by any of a combination of factors; the most important of these are the degree of violence of the shell burst and the burn characteristics of the stars. In simplest terms, a star will ignite when its surface has been raised to its ignition temperature. The star will continue to burn only so long as the burning surface feeds sufficient energy to the next deeper layer of the star, to raise that unignited composition to its ignition temperature. (See Fig- ure 1.) (For a more complete discussion of pyrotechnic ignition and propagation, see reference 1.) Figure 2. Illustration of the effect of air move- ment past a burning star. During some recent tests, this effect was cap- tured on film. Figure 3 shows the explosion of an 8-inch aerial shell that had been suspended in a test stand. (The purpose of this test was to deter- mine its time to explosion and the blast pressure Figure 1. Illustration of a burning fireworks star. produced.) Figure 4 is an enlargement of a portion of Figure 3, showing stars (dark spots) with their flames (light areas) trailing behind. One way in which thermal energy is fed to the next (unignited) layer is for radiant energy from If the amount of energy being fed back is no the flame to be absorbed by the surface of the star longer sufficient to raise the next layer of the star and then conducted more deeply into the star. to its ignition temperature, the burning star will be When a burning star is moving through the air, the extinguished. Among those factors of importance flame will be deflected down wind. (See Figure in determining whether this will happen is the 2.) Thus, in this case, the feedback of thermal speed of the star as it moves through the air. The energy to unignited composition is impeded. Also, faster the star is moving, the more its flame trails the up wind side of the star will be exposed to rel- behind it, thus feeding back less radiant energy. atively cold air. This acts to further cool the burn- Also there is a greater cooling of the star’s surface ing surface. from the air impinging on it. For a given star size and mass, its initial speed is determined by the violence of the shell burst. Thereafter the star slows due to aerodynamic drag forces. Thus, if a star manages to stay ignited during the first brief Selected Pyrotechnic Publications of K.L. and B.J. Kosanke Page 307 Figure 3. Explosion of an aerial shell in a test stand. moments after the shell bursts, it will generally burn completely. Other important factors determining whether a star will be extinguished upon shell burst are as- sociated with the chemical nature of the star. For example, one factor is the amount of heat being produced by the burning composition; another is the amount of energy needed to raise a composition to its ignition temperature. Often star priming is only thought of in terms of aiding star ignition. However, it is also an im- Figure 4. Enlargement of Figure 3 showing the portant aid in the continuation of burning during flames trailing the burning stars. and just after shell burst. (For a more complete discussion of this phenomenon, see reference 2.) When the authors manufactured spherical stars smaller than 3/8 inch. This was felt to be optimum commercially, they concluded that the optimal for two reasons. First, with this amount of prime, amount of rough meal prime was to use as much perchlorate color stars and even strobe stars would as possible without noticeably delaying the visual stay ignited even after emerging from hard- appearance of the star after the shell burst. Gener- breaking shells. Second, rough meal prime (75% ally this was 10–15% of prime (by weight) for potassium nitrate, 15% charcoal, 10% sulfur and stars larger than 3/8 inch, and 15–25% for stars +5% dextrin) is the least expensive composition Page 308 Selected Pyrotechnic Publications of K.L. and B.J. Kosanke used in making stars. The more of it that could be References used without detracting from the star’s perfor- 1) K. L. and B. J. Kosanke, “Pyrotechnic Igni- mance, the less expensive the stars could be made. tion and Propagation: A Review”, Journal of Blind stars are often thought of as failing to ig- Pyrotechnics, Issue 6 (1997). Also appeared nite before the shell bursts. However, as discussed in Selected Pyrotechnic Publications of K. L. above, the stars may have ignited, only to be and B. J. Kosanke, Part 4 (1995 through blown blind by the violence of the explosion of 1997), Journal of Pyrotechnics, Inc., White- the shell. Two easy solutions to the problem are to water, CO (1999). break the shells more softly or to prime the stars 2) K. L. and B. J. Kosanke, “Pyrotechnic more heavily. Primes and Priming”, Proc. 4th International Symposium on Fireworks (1998). Selected Pyrotechnic Publications of K.L. and B.J. Kosanke Page 309 An earlier draft appeared in Fire Engineering, June 1995. Fireworks and their Hazards Thomas J. Poulton, M.D. and Kenneth L. Kosanke, Ph.D. • THOMAS J. POULTON, M.D., is on the faculty of the Department of Anesthesiology at the Albany Medi- cal College, Albany, New York, and formerly served as fire physician for the Topeka (KS) Fire Department. He has been an EMS instructor and fire-service training officer for many years and taught advanced technical rescue courses as an adjunct faculty member at the University of Kansas Fire School. A licensed fireworks display operator, he has been instructing about fireworks for many years and is a member of the Pyrotechnics Guild International. • KENNETH KOSANKE, Ph.D., heads PyroLabs, Inc., a pyrotechnic research laboratory in Whitewater, Colorado. He has authored more than 180 articles on pyrotechnics and fireworks and is a member of three National Fire Protection Association’s technical committees (pyrotechnics, explosives and special effects), the International Pyrotechnics Society, the International Association of Bomb Technicians and Investiga- tors, and the International Association of Arson Investigators. His doctorate is in physical chemistry. “What are fireworks like?” she had asked. “They are like the Aurora Borealis,” said the King, “only much more natural. I prefer them to stars myself, as you always know when they are going to appear....” Oscar Wilde, The Remarkable Rocket Although appreciative audiences may value the Pyrotechnics is part of the field of ‘high energy predictability of fireworks, firefighters, unlike the chemistry’.[1] Pyrotechnics and explosives differ king in The Remarkable Rocket, know that on oc- largely in the rate at which energy (in the form of casion they may not be so reliable. When the first- heat, light, sound, and motion) is released. Pyro- due company finds it is dealing with fireworks, it technic burning and explosion, like all burning, is in an unusual situation that requires specific involve oxidation-reduction reactions. The degree technical knowledge to ensure the safest possible of confinement of highly reactive compounds and outcome. compositions has considerable impact on the be- havior of the material. A mixture that simply Scope of the Challenge burns in the open may explode when contained within the hard covering of a fireworks aerial During the past 15 years, the quantity of fire- shell. works used in the United States has more than The local fire authority usually has at least one doubled to approximately 100 million pounds an- company standing by at major fireworks displays. nually. Although fireworks remain most popular Although the transportation safety experience over the Fourth of July holiday, their use is now with fireworks has been exemplary, motor vehicle common throughout the year at theme parks, fairs, accidents involving trucks carrying pyrotechnic and public events. Performing artists have greatly devices can occur at any time without warning. expanded the use of pyrotechnic displays to en- Thus, firefighters and company officers must be hance the entertainment value of concerts, plays, aware of the hazards of pyrotechnic devices, un- and other stage productions.

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