|MadSci Network: Chemistry|
What an interesting question. Smoke is generally produced by two methods. The first involves pyrotechnic devices, i.e. a mixture that is burned to produce heat and smoke. Smoke grenades are a typical example of a pyrotechnic device.
White and black smoke are produced fairly easily using pyrotechnic compositions. For example, at this site Smoke Screen there are several formulas given for white and black smoke compositions. Some chemicals when burned give characteristic colors but most colored smoke is produced by adding an organic dye to the composition. An important consideration is producing a colored pyrotechnic smoke is to keep the burning temperature of the mixture low enough so that the dye is not burned. In the US, Skylighter sells mixtures that, when mixed with an oxidizer will produce colored smoke. Most companies consider the specific mixture that they use to be a trade secret, so they don't usually provide an exact chemical composition.
The second method of producing smoke in an airshow is to use the heat of the engine or exhaust to vaporize oil, which forms a thick white smoke. Oil is injected into the exhaust of a jet engine or sometimes against the exhaust manifold of a piston engine to vaporize the oil. To color the smoke, dyes are added. For example, this company sells petroleum dyes that they claim are specifically for air shows! The advantage of adding dye to a vaporized oil is that there is much less risk of the temperature getting too high and burning the dye. Also, the organic dyes are probably safer than using some of the inorganic compounds to get a colored smoke; compounds like arsenic and antimony.
Asian Aerospace provides an interesting article on some of the difficulties for those in the business providing smoke oil for air shows. The International Aerobatics Club has a discussion on their web site about providing colored smokes at air shows. It seems that one of the biggest problems with injecting all of that colored dye to get a colored smoke is that when the dye settles to the ground, it colors everything it touches, including cars and people.
Thanks for the question, and good luck with your colored smoke project.
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