It’s not summer in Malta until the night sky is lit up from different village feasts all around the island, and fireworks have become a big part of our culture. In other countries like the USA, fireworks are better known for one-off, annual events such as the 4th of July celebrations that go down every year. This inspired an online video uploaded by Mic which explained how fireworks work, and while we’re aware that there are some differences between how different countries build their fireworks, here’s the basic science behind the pretty lights.
1. It all starts with what’s called an ‘aerial shell’
This capsule holds everything you need to make fireworks. The chemical mix inside an aerial shell can determine what the explosion is going to look (colour and shape) and sound like. Of course, an integral part of the capsule is gunpowder, but it also has small clusters which are called ‘stars’. These are essentially what will later become the sparkles we actually see in the sky.
2. So how do you “design” fireworks?
Designs inside the aerial shell are composed of the ‘stars’, and they are mostly done by hand. The entire design is reproduced (on a much smaller scale) inside the device itself. This means you can either have a random placement, giving you the ‘normal’ circular pattern everyone recognises (fun fact: this type of firework is known as the ‘peony’), or you could make your own pattern. Malta has already toyed with this concept before, and we only keep getting better at it… like Għaxaq’s smiley and emoji fireworks from this year.
3. But how do ‘stars’ light up?
It’s all just one big chemistry shopping list. Each star contains a fuel substance, an oxidiser, a colorant and a binder. The shell’s base is made up entirely of gunpowder, and is placed inside a tube called a mortar. The entire thing is hooked up to a long fuse that extends from the shell all the way outside of the whole thing, and igniting this launches the mortar (and the shell) into the air. Think the classic fuses from Wile E. Coyote and Road Runner cartoons, but in real (and dangerous) life.
4. What happens when the shell shoots up in the sky?
The buildup of gas and pressure propels the shells in the sky, and it goes very high very fast. Think 1,500 feet in the air at speeds of up to 400 kilometres per hour. While all of this is happening, the last part of the fuse, aptly named the ‘time-delay fuse’, would be slowly approaching the gunpowder base. The stars are ignited, expanding the gasses fast than the speed of sound. The sonic boom which is created is what you hear… and what people frequently complain about.
We’d like to remind everyone that fireworks can be as dangerous as they are beautiful. Please do not try any of these steps at home.