The recipe for black powder, the basic material in all fireworks, has remained
the same since it was discovered in China 1000 years ago: seventy-five percent
saltpeter (or potassium nitrate), fifteen percent charcoal, and ten percent
sulfur. Black powder explodes at the relatively slow rate of 1/10 of a second
per foot—making it a "low explosive."
Stars are the precious cargo carried by "aerial" fireworks, like this one. 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
breath-taking flashes of color and light that elicit "ooohs" and "ahhhs" from
even the most jaded spectators.
Fireworks masters, like the Grucci family of Brookhaven, NY, manufacture their
creations by hand, including the hundreds of stars that go into a single
firework. Carefully measured ingredients like perchlorate and black powder are
mixed 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, that are then set out to dry. (Go to our
Hot Science "Pyrotechnics: It's Elemental," and discover which elements of
the Periodic Table are behind the beauty and power of fireworks).
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
(back to Anatomy)
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