How do fireworks make shapes?

The chemistry behind the spectacular patterns in the sky

Modern fireworks can burst into hearts, smiley faces and even a representation of the planet Saturn. The shape comes down to the construction of the firework’s shell (container) and the arrangement of the exploding stars (pyrotechnic pellets) within them. As aerial shells are often spherical, they tend to explode symmetrically. Arranging the stars into the desired shape on a piece of card within the shell makes them explode outwards in that pattern.

 

HIW_inside a firework

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Manufacturers also use multi-break shells that have different compartments inside them, often with stars of various colours and compositions. When these are placed and fused in a specific order, they will explode in sequence to create recognisable patterns and shapes in the sky. However, it’s not an exact science; many displays will fire several copies of the same firework at the same time so that at least one of them creates the desired shape in the audience’s line of sight.

HIW_sparklers science

Sparklers may be great fun, but they can be dangerous if used incorrectly. Always be careful when using them!


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