Many of us around the world will enjoy a firework display tonight (or have already);
but what are the mechanisms behind the magnificent spectacle?The story behind fireworks begins about 2000 years ago in China. Alchemists at the time were in search for an elixir which made them immortal. Obviously, they did not find this- what they did find however was a substance consisting of potassium nitrate, charcoal and suphur; or gunpowder,as we know it. The evolution of fireworks from gunpowder took another 1000 years until a monk named Li Tian realised that if you placed gunpowder into a bamboo tube and ignited it, an impressive explosion on sound and light ensued. Fireworks were born!
The gunpowder is responsible for the trajectory of the firework, but what makes the colours?
The colours we see are attributable to what are aptly known as “Stars”; they are clay like clumps which are about an inch in diameter and within in them are the magic of a firework. They contain four main ingredients; oxidisers, reducers, colourants and binders. When they are ignited, the oxidisers release oxygen which combines with reducing agents where the energy behind the “pop” is generated. As we know, oxygen is like a fuel, so the more oxygen the hotter the explosion, and the hotter the explosion, the more magnificent the colour display. The colourants are usually in the form of metal salts – red is achieved by using lithium carbonate and strontium salts, while magnesium, aluminium or titanium will produce a silver effect. Finally, the binders hold the stars together, making them more stable (and less likely to ignite when they aren't supposed to).
