HOW do fireworks work? And will they one day invent a noiseless firework that is “animal- friendly”? – Lee Scholtz, Westdene
THE fireworks that dazzle us today have their origins in 12th-century China, where the explosive mixture of charcoal, sulphur and potassium nitrate that gives fireworks their “oomph” – known as “black powder”, because of its colour – was invented.
Nick Mitri of Pyro Spectacular in Rivonia, Johannesburg, explained the basic structure of a modern firework. It is put together a little like an onion, with layers of thick paper creating the outer “shell” of the round structure. A “charge” of black powder (which is similar to gunpowder) is packed into the centre of this ball.
This charge will only explode once the firework is in the air, so a second parcel of black powder – known as the “lift charge” – is needed to launch the firework out of the pipe, or “mortar”.
In total, three fuses are needed: one to ignite the lift charge, and the other two (one of which is a back-up fuse) to explode the firework shell in the air.
This is how the explosions occur. The brilliant lights that shower down after the “big bang” are created by a different ingredient. Balls the size of marbles, known as “stars”, are tightly packed around the black powder inside the firework shell. The explosion of black powder sets the stars on fire, and forces them to burst out of the shell.
And the colours? The marble-shaped stars are made of a variety of substances that each create a different colour: aluminium for silver, copper for blue, sulphur for yellow. A multitude of colours is made by layering the various substances, with the colours changing as the fire burns through each layer of the star.
This is a basic recipe for a firework, but there are many variations to amaze and delight us. Sizes range from the 6cm shell, to the real breathtakers measuring 40cm and weighing 45kg. While the light-weights are sent up about 100m, the larger ones go as high as 300m. According to Mitri, United States manufacturers are working on a 120cm model which would be dropped from an aeroplane.
Many of the fireworks are named, perhaps not surprisingly, after flowers. “Peonies” are the ones that burst into points of light, then drift slowly into darkness. “Chrysanthemums” flower into elongated lines of gold light, caused by a “fire trace” that makes “the star actually drip colour”.
In Mitri’s opinion, one of the most beautiful is the “coconut palm”. This firework explodes into a series of “octopus legs” that radiate out from the centre. The effect is created by “fireworks within a firework”, with each mini-firework exploding into a jet of light in separate directions.
The fuses of the lift charge used to be lit by hand – which, in Mitri’s experience, was “more of an adrenaline rush than sky- diving”. However, computers are now being used to detonate the lift charge, making the process far less hazardous, and allowing for more sophisticated choreography.
The mortars for the fireworks are set up in racks (as opposed to the more primitive method of burying them in sand), and linked by cables to the computer. With the flick of a switch, an electric charge heats the fuse head (or “squib”), causing it to explode.
Mitri is doubtful about the chances of an entirely “noiseless” firework being invented. However, technology being developed in the US is at least minimising the noise caused by fireworks. This is thanks to “an air-generated launch system” that uses compressed air to force the firework into the air, thus saving on the initial noise made by the lift charge.
However, as Mitri points out, fireworks, by their very nature, involve an explosion – and, therefore, noise.