The Chemistry Of Fireworks
Fireworks Season
While the 5th of November, Guy Fawkes Night, is the original fireworks night, it is also marks the start of a short season of displays, spanning the nocturnal winter months and marking key calendar and cultural events such as the Winter Solstice and New Year’s Eve. Most of us take these spectacular pyrotechnic shows for granted, but beneath the surface of every firework display lies a complex and fascinating science.
Launch Mechanics And Chemistry
Getting a firework into the air involves more than just lighting a pot of gunpowder; it’s a carefully engineered and orchestrated chemical explosion. A successful firework display involves five key phases: Ignition, Lift Charge, Burst Charge, Colour Production, and Special Effects.
Without the proper coordination of these chemical events, fireworks would simply explode on the ground in an uncontrolled and dangerous jumble of fast-moving, extremely hot debris and blinding light.
Ignition: When a firework is ignited, the heat from the fuse initiates the combustion of the fuel, which is typically charcoal or sulphur (the latter being responsible for the rotten egg smell that sometimes accompanies fireworks). The oxidiser releases oxygen, which combines with the fuel to produce a rapid exothermic reaction, generating heat, light, and expanding gases. Common oxidisers include nitrates, chlorates, and perchlorates.
Lift Charge: The expanding gases from the combustion reaction force the firework shell into the air. This is known as the lift charge, which accounts for the launch velocity and altitude of the firework. As the shell ascends, it reaches a point where a timed fuse ignites the internal components.
Burst Charge: At the peak of its trajectory, the firework’s burst charge, which contains more fuel and oxidisers, ignites. This explosion scatters the fireworks’ contents, including colourants and effect materials, across the sky.
Vibrant And Colourful Light Displays
The vibrant colours you see in fireworks are not random; they are carefully engineered by including different metal salts and metal oxides in the explosive mixture. For example, vibrant reds are derived from strontium salts, orange from calcium salts, yellow from sodium salts, green from barium salts, blue from copper salts, and purple from a combination of copper and strontium salts. The silver colour does not come from silver but rather from white-hot magnesium and aluminium, while white is produced by burning metals like magnesium, aluminium, and titanium.
But why do these metals create different colours when they explode? This is due to the unique arrangement of electrons around the nucleus of each element. During an explosion, these electrons become excited and emit different wavelengths of light (colours) as they release their energy and return to their ground state.
Special Effects
Chemists have learned to exploit different properties of these metal elements to create special effects. For example, aluminium, iron, and magnesium burn at high temperatures and create sparks, which are responsible for the bright sparkling trails and, of course, sparklers!
Organic compounds such as benzoates and salicylates are used to produce whistling sounds in fireworks. These compounds rapidly decompose upon heating, releasing gasses that create the characteristic noise.
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I am a practising HR consultant working with several start-ups on an ongoing and ad-hoc basis in the London and M4 area, and am a Chartered Member of the Chartered Institute of Personnel and Development or CIPD. I am the Director of thecareercafe.co.uk; thecareercafe.co.uk is a resource for start-ups and small business. It includes a blog containing career advice, small business advice articles, HR software reviews, and contains great resources such as HR Productivity Apps.
