The bright colors of fireworks come from salts. When these chemicals are , their electrons absorb energy and then it as light of particular . Strontium produces red, barium green, and copper produces . Blue is the most color to create, copper compounds break down if the is too hot. Gunpowder, invented in China more than a thousand years , provides the explosive power.

Gunpowder was probably discovered by accident. In the ninth century, Chinese alchemists searching for a medicine that would give long life mixed saltpeter, sulfur, and charcoal. Instead of a medicine, they produced a mixture that burned violently. Early texts warned that some experimenters had burned their hands and faces, and even their houses.

The Chinese soon used the powder for celebrations. By packing it into bamboo tubes, they made firecrackers whose loud bangs were believed to frighten away evil spirits, a tradition that continues at Lunar New Year today.

Knowledge of gunpowder spread along trade routes to the Islamic world and reached Europe by the thirteenth century. There it changed warfare, but it also found peaceful uses in mining and road building, where controlled explosions made it possible to break through rock.

For centuries, fireworks could produce only orange and white sparks. Bright reds, greens, and blues became possible only in the nineteenth century, after chemists learned how different metal salts color a flame.