Gunpowder is a way of burning charcoal fast

A look at what makes gunpowder go boom!

Erik Engheim

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Modern gunpowder is corned
Modern gunpowder is corned

A gunpowder explosion is just charcoal burning really fast. You would have gotten the same energy released by burning a lump of charcoal in your BBQ. When coal is burned, it turns into hot carbon dioxide gas. This gas expands to significantly larger volume than the lump of coal which got burned. In this story, we will look at how mixing in saltpeter and sulfur with charcoal to create gunpowder, allows us to burn charcoal much more rapidly than you would achieve in your BBQ.

Rapid combustion produce rapidly expanding gases. If these gases expand within an enclosed space, they will eventually cause the buildup of enough pressure to cause an explosion. In fact, we don’t even need a combustion. If you heat water within an enclosed space, then you can cause an explosion. When water is boiled, it expands to 1600 times the volume of the boiled water. That is the reason boiler explosions were so common during the industrial revolution.

When gunpowder burns, it produces gases which would take up 380 times as much space as the original powder at room temperature. However, the burning also makes the gases hot. Hot gases consume more space. Remember, that is the principle used in hot air balloons. The hot gases from a gunpowder explosion will consume 3000 times the original volume of the powder. As this happens in 25 microseconds, we hear it as a bang.

How much water expands when heated and how much gunpowder expands under combustion
How much water expands when heated and how much gunpowder expands under combustion

The question is: What makes a lump of charcoal burn slowly, while the ground up charcoal in a gunpowder mixture burns extremely fast?

Combustion is about combining a fuel with oxygen. For this combustion to happen, the fuel molecules such as gasoline or coal need to be brought close to each other. The carbon atoms inside a lump of coal cannot burn because there is no oxygen inside the lump of charcoal. The oxygen is only at the surface. Carbon and oxygen combine at the surface, creating carbon dioxide.

Thus, the trick is to find a way to give as many carbon atoms as possible access to oxygen at the same time. In coal mines, that happens occasionally. The…

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Erik Engheim

Geek dad, living in Oslo, Norway with passion for UX, Julia programming, science, teaching, reading and writing.