The chemistry of a fireworks show is a tried and true sequence of events.
First, a base of black powder ignites to shoot the firework into the sky, and lights a fuse on fire. Once the firework is at the pinnacle of its trip, that lit fuse ignites a burst charge that acts like gunpowder. That charge exerts tremendous pressure on the dense package of chemicals, fuel, and glue. Inside, colourful “stars” filled with elements that burn into bright-hot colours explode in midair.
Pyrotechnics expert Mike Tockstein told Business Insider that fireworks are not actually rocketed into the sky.
“We don’t use rockets,” he said. “We use mortars and aerial shells.”
He explained that shells are a safer choice, since rockets can change direction once they leave the launch pad, while shells are locked in to a single trajectory. Nowadays fireworks are typically shot off electronically for large shows, rather than by hand.
Here’s how the whole process happens:
The loud blast in your ears when the fireworks go off is the sound of a sonic boom that’s produced as the gases packed inside the shell expand quicker than the speed of sound, according to the American Chemical Society.
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