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The Challenge: Make fireworks

Animated Roman CandleWe know how a rocket works, but how are Roman candles made?

"Roman candle" is the traditional name for a firework that has been around for centuries. In its simplest form, it's just a cardboard tube with a star sitting inside it. The fuse runs into the tube and ignites a lifting charge, popping the shell out of the open top and into the air where it explodes.

Cutaway of a roman candleThe lifting charge is black powder which when ignited produces a lot of gas pushing the bundle of stars upwards.

The best known Roman candle is the air-bomb which has stars that explode with a loud bang when they reach the right height.

Some Roman candles have more than one shell inside, stacked on top of each other, separated by a lifting charge. The fuse runs down the inside of the tube, igniting each charge in turn. Thus the shells are launched one after the other, with a pause between each one. This is known as a 'multi-shot' candle. The effects can be varied depending on the types of shell inside the tube.