As November approaches, Diwali and Guy Fawkes night are just around the corner, and vibrant sparkles are set to light the skies . But, while you marvel at these dazzling displays, have you ever wondered- what does it take to create that explosion of magic in the night’s sky?
A firework is all about controlled explosions, all of which start in the shell, usually made of plastic or paper. Inside, there are small pellet-like compounds called “stars”, which contain a mix of chemicals, including a fuel and metal salt. The way these stars are arranged will influence the fireworks shape in the sky, whether that's a peony, chrysanthemum or the humble ring. The shell is also divided into sections, each with a specific role to play.
The first of the components is the lift charge, which powers the launch and is usually made of gunpowder. When it ignites, it undergoes a rapid exothermic reaction that creates expanding gases, and intense heat which propels the firework shell upward.
Then, as the firework is launched, a time-delay fuse is lit at the same time. Timing is everything in fireworks, and it’s all controlled by this component. Without it, the fireworks could explode at the ground immediately after being lit, which wouldn’t be very impressive. The fuse burns slowly and precisely to allow the firework enough time to reach the perfect height, and only then does it ignite a second burst charge, to unleash the main explosion.
In this second reaction, as the burst charge ignites, the stars enclosed within the shell are lit to create gorgeous sparks of colour across the sky. The vivid hues come from metal salts in each of the stars, with each compound releasing a different colour when burned- strontium burns red, barium green and copper blue. Sound is, of course, another vital part of the firework experience, and is also created by a chemical reaction! Narrow tubes filled with fast-burning chemicals create high-pitched whistles, while smaller bursts of microstars create the crackling effect, to signal the firework’s detonation.
So, as the days draw shorter, and the air turns crisp, London’s streets and skies will soon come alive with celebration and as you gather to enjoy these spectacular shows, take a moment to appreciate the spectacular blend of culture, chemistry and artistry behind each burst of light- from gunpowder to glitter, we’ve come a long way!