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 for a stoichiometry of nine parts fuel to one part oxidizer. 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 pots. 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 firecrackers. 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, firecrackers containing 50 mg or less of this mixture are legal as consumer fireworks. Safety and handling Flash powders even within