How Potassium Nitrate (Saltpeter) makes a not-so-safe smoke bomb

Thompson’s final pyrotechnic demonstration is to mix sugar (fuel) with potassium nitrate, cook it to a caramel color (to make sure it is mixed very well), add a fuse to the mixture, and light the fuse to cause a small explosion.

Basically, he has demonstrated the power of this basic ingredient which makes up 75% of the type of gunpowder called black powder.

According to Wikipedia, potassium nitrate supplies the oxygen necessary for combustion in gunpowder.

The other ingredients of black powder are charcoal, which provides the fuel, and sulphur, which lowers the temperature of ignition and so speeds up combustion. Source: Wikipedia: Gunpowder.

In Thompson’s experiment, the sugar provides the fuel for this experiment, and caution provides safety.

In researching this experiment on YouTube, you will find the final product called a “smoke bomb.” Here is a video explaining how this project went awry and exploded while being stirred, burning the young scientist.

Smoke Bomb Mistakes To Learn From

Here is a video from a chemistry student at the University of Montana identifying the need for safety goggles, gloves, and an apron or lab coat: Lab Safety Precautions.

Here is a website illustrating this project step-by-step. It answers the question of whether the mixture would smoke without being heated: Steps in making a smoke bomb. The article notes that heating caramelizes the sugar, which process causes moisture to escape as steam. The resulting mixture is drier, and more finely mixed. Careful mixing is an important step in mixing of gunpowder, where charcoal replaces sugar as fuel.

If you use a pan, you will want to be prepared to clean the pan. Take the precaution of pouring water in the pan after you have emptied the mixture onto a non-flammable surface (concrete, or aluminm foil, for example). Source: Making your smoke bomb in a pan on a stovetop.

It should be noted that users of black powder have stressed the need for extreme caution in making black powder. The powder requires exact proportions of ingredients, and hours of careful stirring, to mix the powder in such a way as to not to set off an explosion, possibly losing a limb or dying as a result of careless handling.

Potassium nitrate (saltpeter) has been used as a food additive, serving various purposes, including preservation of meat. The ornithologist, artist and naturalist, John James Audubon, is noted to have salted his food with saltpeter, in his biography.

But you may want to avoid salting your food with saltpeter. It appears the military has used saltpeter in its food until the practice was stopped in 2013. Its purpose was purportedly to lower the libido of military personnel. Military to stop adding saltpeter to chow.

See this link for a satisfying article which explains the derivation of the chemical symbol K for potassium from “kalium,” Mediaeval Latin for potash, and the derivation from an early Dutch word which translates as “pot ashes.”

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We thank Grant Thompson for his “5 Crazy Stunts You Won’t See in School,” the original link for which is here.

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