FIZZ POP BANG!

Peter Gallivan explores the explosive power of fireworks. It's going to go with a bang!

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Picture the scene: a large crowd gathers Plooking expectantly up at a clear and dark sky. Suddenly, with a deafening bang, the sky explodes in a burst of colours. The crowd “oohs” and “aahs”, because watching a firework display is breathtaking. While modern rockets produce a riot of colours, the basic mixture of chemicals inside them is more or less the same as it was 1,000 years ago.

Lucky accidents

The earliest fireworks were created around AD800 in China. The story goes that they were invented by someone who was trying to create a potion for eternal life, but instead ended up with an exploding mixture. These first bangers were powered by poop. They contained three chemicals - potassium nitrate, which was extracted from animal dung and human poo, charcoal (from burnt wood) and sulfur (an element that occurs naturally in rocks). The potassium nitrate was scraped off the side of communal toilets. When packed inside a hollow bamboo tube and set alight, this poo-powered mixture exploded with a loud and smoky (and probably quite smelly) bang.

The mixture, called black powder, forms the basis of all modern fireworks. It is made up of 75% potassium nitrate, 15% charcoal and 10% sulfur. Setting fire to a pile of black powder gives a little bit of a surprising result. You get a quick flash of fire and a quiet fizz - definitely not the loud bang associated with a firework. The boom only happens if the black powder is packed inside something - in the case of a rocket this is usually a thick cardboard tube.

Explosive chemistry