The magic of fireworks!
Fireworks date back to the 7th century and are thought to have been invented in China. The first fireworks in England were displayed at the wedding of King Henry VII in 1486. Now, as well as being an integral part of Bonfire Night celebrations, fireworks can often be seen at New Year, Birthday and Wedding celebrations and frequently form the finale for major events.
Fireworks come in many shapes and sizes and new types are being created all the time. Some of the many varieties are: cakes, firecrackers, cherry bombs, jumping jacks and Catherine wheels.
sparklers, rockets,
A rocket can reach speeds of 150 mph and its shell can reach as high as 200 metres. A sparkler burns at a temperature over 15 times the boiling point of water.
The different effects created by fireworks have names such as ring, spider, peony, palm and horsetail. The variety of colours and noises also thrill many of us. There are now a rainbow of colours and sounds that include bangs, crackles, humming and whistles.
So what happens within a firework to cause us such excitement?
Each firework is a precisely formed assembly of chemicals and fuel, carefully calibrated to produce a particular effect.
Fireworks consist of stars, small clay or dough- like lumps or cubes 3 to 4 cm in diameter, packed into cardboard compartments within
38 the firework shell. Stars contain a blend of
oxidizing agent, reducing agent, metal salt colouring agent and binders. When ignited, the stars produce both sound and light effects.
The power needed to lift each firework into the air is provided by the highly exothermic combustion of black powder. The key to firework success is to trap the heat and gas in the bottom of the shell, which is positioned in a launch tube or mortar, until the trapped gas pressure builds to such a force that when it escapes, it hurls the firework high into the air.
A firework is ignited by lighting the main fuse.
This simultaneously starts both the fast action fuse, and the time delay fuse.
The flight of the firework is powered by a fast burning wick. Where the wick ends, it meets the high explosive components of the firework. In this second stage, there is an instantaneous detonation producing both a loud explosion and a bright flash of colour.
The black powder lift-charge is calculated to exhaust itself precisely when the slow- burning, time-delay fuse reaches the first compartment packed with light-producing stars and black powder.
The tremendous booms heard are the result of the rapid release of energy into the air, causing the air to expand faster than the speed of sound which produces a shock wave - a sonic boom!
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