July 9, 2008 > TechKnow Talk
Fireworks: A Booming Business
Two thousand years ago, a Chinese cook mistakenly mixed charcoal, sulfur, and saltpeter which suddenly burst into flame. Thus, gunpowder was invented. So the story goes, anyway. No one knows for sure how gunpowder was invented, but we do know it happened in China about 2,000 years ago. The story of the cook is plausible, as these ingredients were common in Chinese kitchens at the time.
The advent of fireworks, in the form of the firecracker, did not occur until some 1,000 years later. Many credit the invention of the firecracker to Li Tian of China's Hunan Province about 1000 A.D. The Chinese believed the loud noise of firecrackers had the ability to frighten evil spirits, and employed them for this purpose at births, holidays, and other special occasions. Firecrackers were widely used at New Year's celebrations to drive off evil forces and promote good luck in the New Year, a practice which continues today.
Gunpowder was not brought from its origin in China to Europe until the 13th century, possibly by Marco Polo. The Europeans exploited it for military uses, inventing "black powder" guns and cannons, but it was not until the 18th century that they began manufacturing fireworks and developed colorful aerial bursts for entertainment purposes. By the time of the American Revolution in the 1770s, fireworks displays were common in Europe. The fledgling country celebrated the inauguration of its first president, George Washington, with an aerial fireworks display in 1789.
Today, China remains the world's leading producer of fireworks. President Nixon's efforts in the 1970s to normalize relations with China led to dramatically expanded trade between the countries and opened a huge market for Chinese fireworks in the U.S. Last year, China exported over $200 million of fireworks to the U.S.
A firecracker is simply gunpowder packed into a paper tube with a fuse to ignite it. Charcoal and sulfur form the fuel of gunpowder, while saltpeter (potassium nitrate) is an oxidizer. In other words, the charcoal and sulfur burn explosively when provided sufficient oxygen, which is the role of the saltpeter.
Sparklers enjoyed by children are made of the same active materials, but distributed along a wire to burn more slowly rather than explode. The gunpowder is mixed with a binding material such as starch so it will adhere to the wire and burn at a gradual pace.
The amazing array of aerial fireworks used in a large display all operate on the same basic principle. They are typically composed of a number of "stars." These are lumps of gunpowder held together with a binder, similar to that used in sparklers, but formed into spheres or pellets instead of coating a wire. These are packed around a large amount of loose gunpowder which in turn surrounds a central charge. This central charge is simply a large firecracker.
This "shell" is launched from a mortar using-you guessed it-more gunpowder. The launching explosion lights the fuse of the central charge and sends the shell high into the air. As the fuse burns into the shell it explodes, sending the balls of slower burning powder in all directions and igniting their surfaces. These arc through the air as they continue to burn, showering sparks.
Most fireworks are simply variations on this design. Some shells are sectioned or nested within each other in such a way as to provide multiple bursts. In addition, various patterns may be formed by positioning the gunpowder pellets in specific locations within the shell, thereby controlling the distance and direction each is thrown from the explosion. These and similar techniques give rise to a broad range of effects, known by names such as chrysanthemum, palm, willow, pistil, ring shell, and serpentine.
Colors are created by adding chemical compounds to the powder. For example, strontium and lithium carbonates burn bright red, calcium chloride burns orange, and barium chloride burns green. A very broad range of colors can be produced using the appropriate chemicals.
By the way, while elements such as strontium and barium do have radioactive forms, the materials used in fireworks are not radioactive, despite misinformation to the contrary. Fireworks do produce some smoke and other particulate pollution, though the amount of pollutants released by fireworks is insignificant in comparison to that produced by the burning of fossil fuels (or from forest fires in recent weeks!).
The basic principles of fireworks design have changed little for hundreds of years, though they have become increasingly more sophisticated as well as safer to handle and use. One change that may be coming, however, is the use of compressed air rather than gunpowder to launch the shells. This is safer and allows more precise control of altitude. Since there is no explosion on the ground to light the fuse, the shells are detonated by a timer, which also provides finer control over the timing of the aerial explosions. Compressed air launching is not yet widely used, but given these advantages it may soon be common.
In addition to the Fourth of July in the U.S., large fireworks displays are common around the world on New Year's Eve, a custom derived from the millennium-old Chinese practice. Large displays also traditionally accompany celebrations of Guy Fawkes Night in the UK, Victoria Day in Canada, and the Thrissur Pooram and Diwali festivals in India.
The fireworks used to produce these thunderous, colorful displays are not available to the amateur, but are the sole province of the professional, known as a pyrotechnics expert. Laws governing what types of fireworks may be legally sold and used by the general public vary dramatically from state to state and city to city.
For example, five northeastern states prohibit the sale of all fireworks, even sparklers. On the other side of the spectrum, a few states permit virtually all consumer fireworks, including aerial explosives or rockets, though cities and counties within those states may enact stricter controls. Because state laws vary so widely, many fireworks retailers locate stores near the borders in states with relatively lax laws, enticing buyers from adjacent states.
Fireworks sales in the U.S. are approaching a billion dollars annually, with revenues in 2007 topping $900 million, more than twice 2001 sales. While safer fireworks and stricter laws continue to reduce risks, there were about 9,000 injuries and more than 5,000 fires attributed to consumer fireworks in 2007.