Are you going to see fireworks tonight or this weekend? Whether you’re in your family garden enjoying a few bangers and toffee apples, or watching a dazzling display at a park, take a minute to think about how these exploding rainbows in the sky actually work.

Use your nose

Fireworks often leave a dry, sour smell behind. It’s caused by burning sulphur, an ingredient of gunpowder.

Drawing pictures in the sky

Some of the most amazing firework displays have fireworks in shapes, wowing the audience with hearts, rings, stars, roses and smiley faces. How do they do that? Well, a small bursting charge and a cardboard cut-out of the desired shape are placed in the middle of the “stars”. These burst out in the shape of the cut-out.

Clashing colours

On Bonfire Night, you’ll be dazzled by fireworks of all sorts of colours. How do firework makers do this? Well, it’s all about chemistry. Elements all burn differently — for example, when pure sodium is burnt, it produces a yellow flame. To create different colours, the makers blend elements with gunpowder. If you see a white or silver-coloured firework, it is likely to contain aluminium, magnesium and titanium. Love the moody blue fireworks? That colour is created with copper. Lilac fireworks contain potassium.

What’s inside a firework?

A firework is a shell of plastic or heavy paper. Inside, it is split into compartments by pieces of cardboard. One compartment contains gunpowder, to propel the firework into the sky like a cannonball from a cannon.

Another contains a mixture of metal salts known as “stars”. When heated, these produce light and heat. The gunpowder, when set alight, scatters the stars across the sky.

Slow burners

Watch the fireworks closely. Do you notice that some stay longer in the sky than others? This is because of the make-up of the gunpowder inside. Saltpeter, or potassium nitrate, burns in a quick flash, while charcoal burns very slowly. So if you see a quick burst of colour that fades almost immediately it contains more saltpeter. Long-lasting effects mean there is more charcoal. If you see a lot of glitter in a firework, it’s a sign of more sulphur.

The danger of shellsuits

Shellsuits are not only a crime against fashion, they’re also a hazard around fireworks. Shellsuits are made of nylon, which makes them highly flammable, and easily ignited.

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