Chemical explosives are traditionally divided into two categories: low explosives and high explosives. The black powder used in fireworks is one example of a low explosive. Black powder burns very quickly, but to get it to go bang, we have to contain it. Fireworks hold black powder inside a cardboard or paper tube so that once the powder has burned, the gases burst the container noisily. This is not unlike the action of popcorn, whose steam bursts its kernel. High explosives consist of materials that typically combine the reacting elements in the same molecule.
High explosives do not need to be contained to make their bang. Nitroglycerine, trinitrotoluene, and RDX are high explosives. Los Alamos National Laboratory is engaged in important research into high explosives and has been recognized for making them environmentally cleaner and more stable, which means safer.
Many of the wrenches and other tools used in the factories were also fabricated from wood. Still the factories experienced several terrible explosions.
During his career, Nobel suffered from terrible nitroglycerine headaches and late in his life, as his heart disease led to his death, he was treated with nitroglycerine. Thus, the first break should blow a little before and the third break a little after. If the timing is off, the firework might detonate too close to the ground. Great care is used in designing the fuses and calculating their lengths. Back to main diagram Stars Stars are the precious cargo carried by "aerial" fireworks like the one depicted here.
An unlit star isn't much to look at—just a dull black lump about the size of a jawbreaker. But appearances can be deceiving. When ignited, stars create the breathtaking flashes of color and light that elicit "oohs"and "ahhhs" from even the most jaded spectators.
Fireworks masters manufacture their creations by hand, including the hundreds of stars that go into a single firework.
They mix carefully measured ingredients like perchlorate and black powder with binding and coloring agents: magnesium or aluminum for white, sodium salts for yellow, strontium nitrate or carbonate for red, barium nitrate for green, copper salts for blue, and charcoal or other forms of carbon for orange. The result is a huge slab of dough, which is then cut like a tray of brownies into half-inch cubes; these are then set out to dry.
Stars can be extremely dangerous if not handled and stored with care. A sharp blow can detonate one. Oil from nearby machines can combine with certain chemicals to create an explosive gas. Even synthetic clothing, which generates static electricity, can create sparks capable of detonating the fragile shells.
Firework makers must stick to wearing cotton—all the way down to their underwear. Back to main diagram Black powder The recipe for black powder, or gunpowder, the basic material in all fireworks, has remained the same since it was discovered in China about 1, years ago: 75 percent saltpeter potassium nitrate , 15 percent charcoal, and 10 percent sulfur.
Black powder lends itself to fireworks because it's a "low explosive," meaning its detonation velocity is less than about yards per second. Fireworks makers can also control the powder's rate of burn in several ways. One way is by manipulating the size of its grains: Fine grains burn more quickly than coarse grains. Back to main diagram Launch tube Most fireworks are launched from rows of steel tubes secured in troughs of sand.
The tubes, or "mortars," are three times as long as the firework shells but have the same diameter. If a firework doesn't fit snugly into its launch tube, the pressure created by the lift charge will escape, and the firework can misfire.
Main fuse During the Renaissance, when fireworks as we know them were invented, pyrotechnicians lit their creations with tissue paper rolled around a trail of black powder. Later, string embedded with gunpowder was used. Today, electrical wires connect fireworks to a master control board.
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