Firecrackers explode into the night, and the sky fills with starbursts.

Want to explain the science of fireworks and sparklers?

HOW FIREWORKS WORK

By Cristy Burne

Ka-BOOM!

Don’t you just love the big bangs, wild explosions and bursting colours of a firework display?

But how does a firework work?
Let’s find out.

Simple fireworks are shaped like hollow balls and filled with fuel to make them explode. More tricky fireworks have different fuels hidden between different layers. Only one layer opens at a time, kind of like “Pass the Parcel.”

Chemical starbursts
Each firework is packed with tiny stars—little packages about the size of a marble that burn to make a bright starburst in the sky. There can be hundreds of stars in just one firework.

Inside each star are chemicals called explosives, which help the star to explode, and chemicals called metal salts, which make the star a bright colour.

Burn, baby, burn
When each star explodes, the heat of the explosion makes the metal salts burn. Different types of metal salt burn with a different coloured light. Iron salts produce gold-coloured starbursts, and aluminium salts give off bright white starbursts. Ordinary table salt contains a metal called sodium, which produces bright orange starbursts when it burns.

Why do metals give off light when they get hot?
When you heat something, you give it extra energy. This energy is heat energy. Metals can change heat energy into light energy by giving off coloured light.

What about sparklers?
Sparklers are just like other fireworks. They burn iron powder to get the bright golden light. Sparklers burn slowly because they don’t have a lot of fuel. Firecrackers explode because so much furl burns all at once!

Did you know?
Fireworks contain titanium, the same stuff that some spacecraft are made out of. Titanium is included to give the big BANG sound of fireworks. When titanium is ground up like a powder, it burns really quickly, giving a huge ka-BOOM!!!

Up, up and away
Setting up for a big fireworks display is a huge job. Each firecracker must be loaded into a metal or plastic tube, called a mortar, which is like a small cannon. Inside the mortar, at the bottom, is an explosive powder. When you light the firecracker, the powder explodes and pushes the firework out of the mortar, blasting it into the sky.

While the firework is shooting up into the air, its fuse is still burning. The fuse is long and narrow, like a piece of string, and it burns right into the heart of the firecracker. As the cracker soars higher into the air, the fuse burns shorter, and gets closer to the fuel at the centre of the firework. Just before the cracker has reached its highest point, BANG – the fuse reaches the fuel and the firework explodes in mid-air.

This article first appeared in CSIRO’s Scientriffic magazine.
Thanks to bestanimations.com for the terrific fireworks gif