Fireworks 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