Although fireworks are still as popular as ever, at least some of the science behind them was developed in China hundreds of years ago, when a chemical composition known as black powder was discovered. Before the 1830s, the only colors were orange and white. As knowledge about chemistry grew, so did the palette of colors available. Now, through the combination of various chemicals and metals we are able to see colorful displays that seem to get more intricate as each year passes.
This explosive charge may contain more reactive and more powerful oxidizers, such as potassium chlorate (KClO3) and perchlorate (KClO4), to produce a more rapid reaction and a bigger bang. In addition, the explosive bang of fireworks is also often due to the use of black powder. In this case, however, the powder is contained in a packing, which allows it to build up significant heat and pressure before the packet ruptures, so as to generate a bang rather than a propulsive force.
Black powder used to cause the firework explosions produces an orange flash. Before the 1830s this is how the color was produced. Black powder is still the most common exploding agent in fireworks, but the colors are now created using chemical compounds instead.
The way we see the color explosions comes from a few components. Iron makes the colors sparkle and chlorine affects the brightness of the colors. Each chemical combination is carefully put together to produce the desired color and effect. The black powder or explosive agent determines how far the color extends. The coloring agents are responsible for what color is shown and the other compounds dictate how the color appears. The star effect commonly seen is a result of zinc.
Some colors are produced from their own chemical solutions, while others can be achieved by mixing primary color solutions. Barium chloride dihydrate makes a bright green color, and orange is now made from calcium. Purple is just a combination of the red and blue compounds. Gold is produced by a blend of iron, carbon and charcoal or lampblack. Silver comes from aluminum, titanium or magnesium.
A firework is designed a bit like a rocket, with a hole at the base. It is a mixture of 15 percent charcoal and 10 percent sulfur, which serves as fuel, and 75 percent potassium nitrate (KNO3), which provides oxygen for the combustion reaction. As hot gases are expelled out from the base, they propel the firework upward. The substance that gets fireworks airborne is black powder, also known as gunpowder. When ignited, these chemicals burn rapidly and produce large quantities of hot gases inside a firework.