The History & Science Behind Fireworks

The History & Science Behind Fireworks

(The internal structure of an aerial shell)

Do you know how fireworks were invented? Legend tells of a Chinese cook who accidentally spilled saltpeter into a cooking fire, producing a beautiful flame. Saltpeter, an ingredient in gunpowder, was used as a preservative for meats and was commonly found in kitchens of the period. The other gunpowder ingredients, charcoal and sulfur, also were common in early fires. Though the mixture burned with a pretty flame in a fire, it exploded when it was enclosed within a bamboo tube.

Historians believe the invention of gunpowder occurred about 2000 years ago, with exploding firecrackers produced later during the Song dynasty (960 A.D. – 1279 A.D.) by a Chinese monk named Li Tian, who lived near the city of Liu Yang in the Hunan Province. These firecrackers were bamboo shoots filled with gunpowder. They were used during the New Year ceremony to scare away evil spirits.

puskaporModern fireworks are created with an emphasis on light and color, but loud noise (known as “gung pow” or “bian pao”) was desirable in a religious firework, since that was what frightened the spirits. By the 15th century, fireworks were a traditional part of many other celebrations, such as military victories and weddings.

Soon, the Chinese were using gunpowder for more than just fireworks. Handcarved wooden rockets, shaped like dragons, shot rocket-powered arrows at the Mongol invaders in 1279. Marco Polo is credited with bringing gunpowder to Europe in the 13th century, although crusaders also brought the information with them.

(Different chemicals produce a spectrum of color)

The Science:

In their simplest form, firecrackers are just gunpowder wrapped in paper, with a fuse. Gunpowder consists of 75% potassium nitrate (KNO3), 15% charcoal (carbon) or sugar, and 10% sulfur. The materials will react with each other when enough heat is applied. The charcoal or sugar is the fuel. Potassium nitrate is the oxidizer, and sulfur moderates the reaction. Carbon (from the charcoal or sugar) plus oxygen (from the air and the potassium nitrate) forms carbon dioxide and energy.

When most people think of ‘fireworks’ an aerial shell probably comes to mind. These are the fireworks that are shot into the sky to explode. Some modern fireworks are launched using compressed air as a propellent and detonated using an electronic timer, but most aerial shells remain launched and exploded using gunpowder. Gunpowder-based aerial shells essentially function like two-stage rockets. The first stage of an aerial shell is a tube containing gunpowder, that is lit with a fuse much like a large firecracker. The difference is that the gunpowder is used to propel the firework into the air rather than explode the tube. There is a hole at the bottom of the firework so the expanding nitrogen and carbon dioxide gases launch the firework into the sky. The second stage of the aerial shell is a package of gunpowder, more oxidizer, and colorants. The packing of the components determines the shape of the firework.