All About Fireworks

The earliest unequivocal documentation of fireworks dates back to 12th century China, where they were first used to frighten away evil spirits with their loud sound ("bian pao") and also to pray for happiness and prosperity.

Eventually, the art and science of firework-making developed into an independent profession of its own. In ancient China, pyro-technicians (firework-masters) were well-respected for their knowledge and skill in mounting dazzling displays of light and sound.

Fireworks may have also led to the use of military rockets in China. It was recorded in 1264 that the speed of the rocket-propelled 'ground-rat' firework frightened the Empress Dowager Gong Sheng during a feast held in her honor by her son Emperor Lizong of Song (r. 1224–1264). By the 14th century, rocket propulsion had become common in warfare, as evidenced by the Huolongjing compiled by Liu Ji (1311–1375) and Jiao Yu.

Cultural Contexts

Since then, any event -- a birth, death, wedding, coronation, or New Year's Eve celebration -- has become a fitting occasion for noisemakers.

Amédée-François Frézier published a "Treatise on Fireworks" in 1706. In this treatise, Frézier studied the recreational and ceremonial uses of fireworks, rather than their military uses. The book became a standard text for fireworks makers.

Music for the Royal Fireworks was composed by George Frideric Handel in 1749 to celebrate the Peace Treaty of Aix-la-Chapelle, which had been declared the previous year.

How Fireworks Work

The sparkler provides bright, sparkling light from a firework, and the firecracker creates an explosion.

Firecrackers consist of either black powder (also known as gunpowder) or flash powder in a tight paper tube with a fuse to light the powder. Black powder contains charcoal, sulphur, and potassium nitrate. A composition used in a firecracker might have aluminum instead of or in addition to charcoal in order to brighten the explosion.

Sparklers are very different from firecrackers. A sparkler burns over a long period of time (up to a minute) and produces extremely bright and showery light. Sparklers are often referred to as "snowball sparklers" because of the ball of sparks that surrounds the burning portion of the sparkler.

A sparkler consists of several different compounds: A fuel, an oxidizer, iron or steel powder and binder. The fuel is charcoal and sulphur, as in black powder. The binder can be sugar or starch. Mixed with water, these chemicals form a slurry that can be coated on a wire by dipping, or poured into a tube. Once it dries, you have a sparkler. The fuel and oxidizer are proportioned, along with the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker.

It is very common for fireworks to contain aluminum, iron, steel, zinc, or magnesium dust in order to create bright, shimmering sparks. The metal flakes heat up until they are incandescent and shine brightly or, at a high enough temperature, actually burn. A variety of chemicals can be added to create colors.

Chemistry of Firework Colors

Creating firework colors is a complex endeavor, requiring considerable art and application of physical science. Excluding propellants or special effects, the points of light ejected from fireworks, termed 'stars', generally require an oxygen-producer, fuel, binder (to keep everything where it needs to be), and color producer. There are two main mechanisms of color production in fireworks -- incandescence and luminescence.

Incandescence

Incandescence is light produced from heat. Heat causes a substance to become hot and glow, initially emitting infrared, then red, orange, yellow, and white light as it becomes increasingly hotter. When the temperature of a firework is controlled, the glow of components, such as charcoal, can be manipulated to be the desired color (temperature) at the proper time.

Metals, such as aluminum, magnesium, and titanium, burn very brightly and are useful for increasing the temperature of the firework.

Luminescence

Luminescence is light produced using energy sources other than heat. Sometimes luminescence is called 'cold light', because it can occur at room temperature and cooler temperatures. To produce luminescence, energy is absorbed by an electron of an atom or molecule, causing it to become excited, but unstable. When the electron returns to a lower energy state, the energy is released in the form of a photon (light). The energy of the photon determines its wavelength or color.

Sometimes the salts needed to produce the desired color are unstable. Barium chloride (green) is unstable at room temperatures, so barium must be combined with a more stable compound (e.g., chlorinated rubber). In this case, the chlorine is released in the heat of the burning of the pyrotechnic composition, to then form barium chloride and produce the green color. Copper chloride (blue), on the other hand, is unstable at high temperatures, so the firework cannot get too hot, yet must be bright enough to be seen.

Quality

Pure colors require pure ingredients. Even trace amounts of sodium impurities (yellow-orange) are sufficient to overpower or alter other colors. Careful formulation is required so that too much smoke or residue doesn't mask the color. With fireworks, as with other things, cost often relates to quality. Skill of the manufacturer and date the firework was produced greatly affect the final display (or lack thereof).