Fireworks

Background

A firework is a device that uses combustion or explosion to produce a visual or auditory effect. Modern pyrotechnics also includes devices similar to fireworks, such as flares, matches, and even solid-fuel rocket boosters used in spaceflight.

The earliest ancestors of fireworks were paper or bamboo tubes filled with finely grourid charcoal and sulfur used in China two thousand years ago. These tubes produced a flash of fire and smoke when ignited, but no explosion. True fireworks did not exist until saltpeter was added to the mixture to create black powder, the first chemical explosive, one thousand years later. Black powder was probably first made in China, but some scholars suggest that it may have been invented by the Arabs.

The Chinese used black powder for fire-works, signals, and weapons such as bombs and rockets. Black powder was introduced to Europe in the 14th century as an explosive for both fireworks and guns. It was applied to mining and roadbuilding projects by the late 17th century. Black powder was used for gunpowder until it was replaced by nitrocellulose in the late 19th century, and (for industrial purposes) by dynamite in the early 20th century, but it is still used in fire-works today.

Fireworks in China evolved from simple firecrackers to the extravagant displays witnessed by European explorers in the 16th century. In Europe, fireworks began with military explosives adapted for use in celebrating victories and progressed to the elaborate productions designed by Italian pyrotechnists in the 16th, 17th, and 18th centuries. (Even today, most of the large fire-work companies in the United States are run by Italian-American families.) These Italian fireworks were usually shown on lavishly decorated wooden sets, often floating on bodies of water, both for safety and to reflect the beautiful displays. On the other hand, German fireworks of the time were usually shot into the air, much like today's fireworks.

Although the firework displays of the Italian masters were extremely complex and impressive works of art, the technology of the time limited their color and brightness. During the 19th century, the introduction of aluminum and magnesium greatly increased the brightness, while the development of potassium chlorate by the French chemist Claude-Louis Berthollet (who was trying to improve the gunpowder used by Napoleon's troops) made it possible to produce more intense colors.

Fireworks came to the New World with the earliest settlers, and have been used to celebrate Independence Day, July 4, since the earliest days of the United States. During the early 20th century these fireworks became bigger, more powerful, and dangerous. Between 1900 and 1930 more than 4,000 people were killed by fireworks. Federal and state governments began regulating the use of fireworks in the 1930s. Explosives are classified as Class A (dangerous substances such as dynamite and TNT), Class B (fireworks used for professional displays) and Class C (smaller fireworks intended for private use.) Class C fireworks must not contain more than 50 milligrams of explosive. Some states allow all Class C fireworks, some allow only "Safe and Sane" fireworks (Class C fireworks that do not move or leave the ground), and some states or counties and cities ban the private use of all fireworks. Some very dangerous fireworks, such as cherry bombs, M-80s, and silver salutes, are banned in all states, but continue to be made and sold illegally. Most firework deaths and injuries in the United States today are caused by these illegal devices.

While the private use of fireworks is heavily restricted, public displays have become more and more elaborate. Computers are used to time fireworks precisely, so they can be choreographed in time to music. Lasers are sometimes used to produce unique visual effects. Today fireworks are made and displayed around the world, particularly in Europe, Latin America, the United States, and Japan.

Raw Materials

A modern firework consists of a shell of plastic, papier-mache, or heavy paper surrounding compartments separated by cardboard. A small compartment at the base of the shell contains black powder to propel the firework into the sky from a mortar made of iron, aluminum, plastic, or heavy cardboard. A larger compartment contains chunks of a mixture of chemicals that produce light and color when heated. These chunks are known as stars. In American and European fireworks the stars are mixed with black powder inside a cylindrical compartment. The black powder explodes to ignite the stars and scatter them across the sky. In Asian fireworks the stars surround the black powder in a spherical compartment to produce a more symmetrical display. Instead of black powder and stars a compartment may contain flash powder, which produces a sudden bright light and loud bang. The various compartments in a firework are attached to fuses made of threads mixed with grains of gunpowder.

Black powder consists of a mixture of salt-peter (potassium nitrate), charcoal, and sulfur in a 75 to 15 to 10 ratio by weight. Flash powder consists of a mixture of potassium chlorate or potassium perchlorate, sulfur, and aluminum. Stars consist of a fuel that burns to provide heat, a coloring agent that provides color when heated, and an oxidizer to burn the fuel. Fuels may be slow-burning such as charcoal, dextrin (derived from corn starch), or red gum (a tree secretion) to produce a dim, long-lasting display, or fast-burning, such as aluminum, magnesium, or titanium, to produce a bright, short-lasting display. Sugar may be used as a fuel to produce smoke. Coloring agents include aluminum, magnesium, or titanium (white), carbon or iron (orange), sodium compounds (yellow), copper compounds (blue), strontium carbonate (red), and barium nitrate or barium chlorate (green). Oxidizers are highly reactive oxygen-containing compounds such as potassium perchlorate or ammonium perchlorate. They also contain chlorine, which reacts with the copper, strontium, and barium compounds in the coloring agents to produce the unstable chlorides of these elements which actually provide the color.

The Manufacturing
Process

Making the stars

• 1 The ingredients used to prepare stars are obtained from chemical supply companies and stored in barrels. At the time of mixing the chemicals are scooped out of the barrels, weighed, and sifted twice through brass screens to remove lumps. (Brass is used because it does not produce sparks.) The sifted powders are placed on a large sheet of paper and gently mixed by hand. The powders may also be mixed inside a rotating drum or a stationary container with rotating paddles. These devices must be used with great care to avoid generating heat through friction or trapping bits of powder between moving parts.
• 2 The mixed powder is placed in barrels and taken from the mixing room to the cutting room. Water is mixed with it to form a soft dough. Lumps of the dough are scooped into large paper-lined wooden molds shaped like loaves of bread. The dough is packed firmly into the mold with a wooden mallet. (The wet dough is much safer to manipulate than the dry powder.)
• 3 The loaves of dough, weighing about 35 pounds (16 kg) each, are unmolded onto a workbench covered with heavy cardboard sprinkled with black powder. The loaves are cut in one direction to form slices then cut in the other direction to form dice. The dimensions of the dice may be anywhere from 0.06-2 inches (0.16-5 cm). The black powder adheres to the wet dice and will help them burn when the firework is ignited. The dice are allowed to dry on papercovered screens.

Making the breaks

• 4 The dried dice are now stars. They are moved to the packing room to be placed into cardboard containers. A hollow cardboard tube is placed in the center of the cylindrical container and stars are gently poured around it. A large container may hold as many as 900 stars (about 4.4 pounds [2 kg]). When the container is full, black powder is poured inside the hollow tube and the tube is removed. The powder fills the spaces between the stars, and will serve to ignite and scatter them. A paper cap is placed on the filled container, now called a "break."
• 5 The break is wrapped with heavy string, a process known as spiking. Spiking is done by tying one end of a large spool of string to the break and winding the string around it. When the break is completely covered, the string is cut and tied. Some breaks are not spiked, but are made instead of plastic or heavier cardboard to withstand the stress of being launched. A time fuse (a short, slow-burning fuse that causes the break to explode a certain amount of time after it is launched) is inserted into the break, and it is wrapped in heavy paper. The wrapped breaks are moved to the pasting room to be wrapped in heavy, paste-soaked paper, then allowed to dry for about two days. The paper hardens as the paste dries to form a strong, tight seal.
• 6 Some breaks, known as salutes, are filled with flash powder rather than stars and black powder. Flash powder is mixed in much the same way as the chemicals used to make stars. It is then poured into cardboard containers that are thicker and stronger than other breaks. This allows more pressure to build up before the salute bursts, resulting in a louder bang. These salutes are then spiked and pasted like other breaks.

Making the shells

• 7 The dry breaks are moved to the finishing room to be assembled into shells. The simplest shells consist of a small compartment of black powder combined with a single break. Due to their spherical structure, Asian shells always contain only one break. Because American and European shells are cylindrical, more than one break can be stacked together, so that the shell will display multiple bursts of different colors when it explodes. Multi-break shells usually consist of a small compartment of black powder, three or four colored breaks, and a salute. Some large shells contain as many as 10 breaks, and at least one gigantic shell has been made holding 22 breaks. The shell is assembled by stacking the components together, attaching a starting fuse (a long, fast-burning fuse used to ignite the black powder that launches the firework), wrapping them in heavy paper, and tying the package together with string. The completed firework is then labeled and stored until needed.

Making small fireworks

• 8 Small fireworks, intended for private use, are made in much the same way as large ones, but they are generally simpler in construction and contain much less explosive. Small fireworks include firecrackers (paper tubes holding a small amount of explosive), fountains (paper cones filled with chemicals which release colored sparks), and Roman candles (long paper tubes filled with a small amount of explosive and several small stars which shoot out one at a time). Some small fireworks contain no explosive at all and may be as simple as a single chemical wrapped in paper or foil. Examples include smoke balls (filled with a chemical that releases colored smoke) and snakes (filled with ammonium dichromate, which slowly burns and produces a long trail of ash). Sparklers are made by dipping a metal wire in a slurry containing a fuel, an oxidizer, a coloring agent, and aluminum granules, which provide the sparks.

Launching the fireworks

• 9 Professional fireworks are usually launched by the same companies who make them. If a set piece (a ground-based display that forms a picture or words with colored flares called lances) is to be used, the design to be formed is sketched on graph paper and sent to carpenters who build a wooden frame with thin wooden slats in the shape of the design. If music will accompany the fireworks, the timing of the display is planned to match the tempo of the music.
• 10 Several hours before the show begins (or a few days in advance, for a very large show), the crew arrives with all the necessary equipment, including fire extinguishers and first aid kits. Mortars to launch the shells are placed in their proper places. Large ones are placed in holes dug in the ground or in steel drums filled with sand. Smaller mortars are placed in wooden racks. The proper shell for each mortar is loaded in place. The frames for set pieces are assembled, lances are attached to the slats, and fuses are attached to the lances. When the display begins, the lances and mortars are lit at the proper times, either with long hand-held flares or with electrical wires attached to a central switchboard. After the show, the crew safely destroys any unexploded duds.

Quality Control

The most important quality control factor in making fireworks is safety. Firework factories are protected from intruders by chain-link fences, barbed wire, locked gates, steel doors, and tamper-proof locks. Within these factories, numerous precautions are taken to prevent accidents.

Electricity is the greatest danger. A single small spark can set off a roomful of explosives. All electrical outlets are located out-side the building. To avoid generating static electricity, all workers must wear 100% cotton clothing. They touch a copper plate before they enter a building to remove any static electricity they may be carrying. Elastic straps with wires trailing to the graphite floor are worn around the worker's calves, to drain static electricity away to grounding rods buried beneath the building. All work is halted and all workers leave the building if there is any possibility of an electrical storm approaching.

Many other safety measures are used. All work is done by hand, to avoid machines that could produce heat or sparks. In the winter, buildings are heated with hot water rather than hot air, which could cause an explosion. The buildings are small, so no one is more than one or two steps away from an exit. All exits have doors that open wide at the slightest touch. Explosive chemicals are never mixed when wet, because when they dry out they may release gases that could ignite them.

Where To Learn More

Books

Brenner, Martha. Fireworks Tonight! Hastings House, 1986.

Plimpton, George. Fireworks. Doubleday, 1984.

Periodicals

Begley, Sharon. "Up in the Sky! It's…Hearts! Stars! Bow Ties!" Newsweek, July 9, 1990, p. 60.

Conkling, John A. "Pyrotechnics." Scientific American, July 1990, pp. 96-102.

Kozlou, Alex. "First Family of Fireworks." Discover, July 1990, pp. 40-45.

—Rose Secrest

Fireworks

One of the most beautiful and entertaining uses of fire occurs in firework displays. Fireworks need a source of combustible material for energy such as black powder, a mixture of charcoal, sulfur, and saltpeter (an old name for potassium nitrate), or smokeless powder such as cellulose nitrate. In addition, fireworks contain substances that give off bright, colorful light when heated. A common example of such material is sodium in table salt. If salt is sprinkled into a flame, an orange color appears. The colored flame is a result of electrons in sodium ions absorbing energy and moving up to higher energy levels and then falling back to their ground state, emitting specific amounts of energy that correspond to colors of light. For centuries, this phenomenon has been the basis of flame tests in chemistry laboratories.

Chemical ingredients of fireworks are chosen to produce specific colors. Barium compounds produce green colors when heated, copper salts produce green and blue flames, sodium salts are yellow in flame, lithium compounds produce red colors, magnesium metal produces brilliant white light when burned, and strontium compounds produce brilliant red colors. Salts used contain both metallic cations and nonmetallic anions . Anions such as chlorates, perchlorates, and nitrates also contribute oxidizing power to the chemical mixture.

While the metallic element dictates the color produced, the compound that contains the element has a profound effect on the type of flame. Calcium does not produce an exciting color by itself, but it enhances colors of other substances. Chlorine does not produce colored flames by itself, but the presence of chlorine greatly enhances the development of color from metallic elements. Chlorine-containing substances such as chlorate or perchlorate oxidizers or organic chlorine compounds such as polyvinyl chloride or hexachlorobenzene provide chlorine atoms to enhance volatility and light emission. Certain substances are included for specific effects. Iron filings sparkle and flash when mixed with other burning materials; the metallic iron oxidizes to produce Fe₂O₃, a process that produces a large amount of energy sufficient to cause the reacting iron particles to glow. Titanium metal is also used for production of sparks. Zinc is used in some smoke formulas and to produce star effects.

Fireworks consist of a source of energy such as a mixture of a fuel and an oxidizing agent that react to produce high temperatures and some substance that will emit brightly colored light. One of the simplest firework devices is a sparkler. Sparklers typically consist of a metal wire coated with a mixture of fuel and an oxidizer (mixed in proportions to allow burning), iron filings, and a glue to hold the components together. When the sparkler is ignited, the fuel and oxidizer burn, heating the iron filings so that they sparkle. Other substances such as zinc or magnesium alter the character of the sparks.

Firecrackers contain flash powder (a mixture of an oxidizer such as potassium chlorate or perchlorate and powdered aluminum or magnesium) or black gunpowder in a paper tube. An attached fuse ignites the flammable mixture, which burns explosively, producing gases that rapidly build up pressure and burst the container. Aluminum and magnesium components produce brighter flashes.

Aerial fireworks usually are of two types, aerial shells fired from tubes and the traditional skyrocket. Rockets are made of cardboard tubes filled with a mixture of fuel and oxidizer in proportions that allow continuous burning rather than explosion. Expulsion of gases from the tube propels it skyward. Rockets often contain explosive charges to explode after the propellant charge burns out; the composition of the explosive charge determines the colors produced.

Aerial shells are small balls of explosive material fired from a steel or cardboard tube or stand. A lifting charge throws the ball skyward, and the explosive charge fires when the embedded fuse burns down after a time period appropriate for the shell to reach the desired altitude. The shell usually contains a bursting charge and stars made up of cubes or spheres of material that will burn, sparkle, or explode. Multibreak shells are made up of combinations of shells designed so that the explosion of one shell ignites the next.

Shells designed to explode with a bang are called reports or salutes. The whistling effect of some devices is produced by packing techniques that cause intermittent burning. Specialized shells designed to burst forming patterns such as hearts or circles are made by surrounding the break charge with pellets containing explosive charges. When the break charge explodes, the pellets are blown outward, producing a pattern.

In addition to their value as entertainment, pyrotechnics have military applications as signaling, training, and combat devices. Burning naphthalene and anthracene produce black smoke that can be used to screen off an

area, but may be dangerous in populated areas. White smoke produced by vaporizing zinc chloride or oil or burning phosphorus is sometimes used to provide cover during combat; the hydrolysis of silicon chloride (SiCl₄) produces a white smoke as well.

SiCl₄ + H₂O → SiO + HCl

The moisture in the air is usually sufficient for producing the desired reaction. Colored smokes for signaling are usually produced by volatilization of organic dyes. Burning mixtures that provide enough heat to vaporize the dye, but not enough to decompose it, are chosen. Dyes chosen must be volatile, but nontoxic.

A simple and safe home experiment can be carried out by squeezing an orange peel near a candle flame. The oils of the peel produce tiny flashes of light as they burn. Bananas contain large amounts of potassium; a banana peel in a bonfire shows the characteristic violet color of potassium flames.

see also Chemistry and Energy; Explosions.

Dan M. Sullivan

Bibliography

Conkling, John A. (1985). Chemistry of Pyrotechnics. New York: Marcel Dekker Inc.

Donner, John (1997). Professional's Guide to Pyrotechnics: Understanding and Making Exploding Fireworks. Boulder, CO: Paladin Press.

Dotz, Warren; Mingo, Jack; and Moyer George (2000). Firecrackers: The Art and History. Berkeley, CA: Ten Speed Press.

Internet Resources

National Council on Fireworks Safety. Available from <http://www.fireworksafety.com>.

fire·work / ˈfīrˌwərk/ • n. a device containing gunpowder and other combustible chemicals that causes a spectacular explosion when ignited, used typically for display or in celebrations. ∎  (fireworks) a display of fireworks: they were oohing and aahing as if they were watching the fireworks. ∎  (fireworks) fig. an outburst of anger or other emotion, or a display of brilliance or energy: when you put these men together, you're bound to get fireworks.

fireworks, an old naval term which embraced any means of setting fire to an enemy ship during battle. They included fire pots, fire-balls (cannon balls heated to red heat in a brazier before being fired), fire pikes (boarding pikes with burning tow attached which were thrown javelin fashion on board an enemy), arrows similarly tipped, etc. Fireships were not included in this general description, although their contents were.

See also warfare at sea.

163. Fireworks

pyrotechnics, pyrotechny

1 . the art of making and using fireworks.

2 . a brilliant and dazzling display, as of eloquence, wit, virtuosity, etc. —pyrotechnic , pyrotechnical , adj.

pyrotechnician

a person skilled in the use and handling of fireworks. Also pyrotechnist .

Fireworks. Fantasy, Op.4, for large orch. by Stravinsky. Comp. 1908, f.p. St Petersburg 1909.

fireworks see pyrotechnics .

FIREWORKS

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