Whether it’s the Fourth of July, Guy Fawkes Night or New Year’s Eve, you’re sure to see the sparking light of nearby fireworks, followed quickly by their boisterous booms. But igniting colourful chemicals and shooting them into the sky isn’t a new tradition by any means. The first fireworks were hurtling into the sky in around 600 BCE in ancient China. Ancient alchemists discovered that mixing potassium nitrate, sulphur and charcoal produced a black powder that’s now referred to as the ‘first gunpowder’. When this powder was stuffed into a bamboo stick and ignited, it created the first firework propulsion system. Early fireworks were used to celebrate weddings, births and even to ward off evil spirits.
Modern fireworks still use black powder, but now incorporate small pellets of packed minerals, called stars, to produce colourful explosions. When the chemicals in the stars are heated, the electrons making up their atomic structures are excited and release energy in the form of different wavelengths of light. For example, when a copper-filled star ignites it burns a brilliant blue colour. Stars are held within a shell, often concealed within a rocket, and are placed in a launching tube called a mortar. A pile of black powder beneath the shell is ignited, and its combustion generates enough force to send the shell flying into the sky before another charge inside the shell combusts, igniting the shells, and the stars within them. If the stars inside are arranged in a particular orientation or design, the erupting fireworks will also resemble that design. If the stars are arranged to look like a heart in the shell, the resulting firework will also resemble a heart.