Putting the 'pow!' in the Fourth of July
Few things are as tempting as a baseball stadium's perfect grass. The Oakland A's have just defeated the Kansas City Royals, and thousands of happy Oakland fans are flooding the outfield. Parents chat on blankets, kids chase one another, and truly dedicated fans visit the spot where Miguel Tejada plays shortstop. But when the music starts, all eyes turn toward the sky.Skip to next paragraph
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The darkness above the stadium is suddenly full of light - bright fronds of silver, glowing rings of green, sparkling blasts of red. The colorful explosions are perfectly timed, aerial drumbeats to the music. On the field, a chorus of "oohs," "aahs," and "wows!" burst from the audience. The biggest crowd-pleaser is a shell that explodes into a perfect smiley face.
How do they DO that?
Jeff Thomas is the man behind the "boom." Mr. Thomas has been a pyrotechnician (PYE-roh-tek-ni-shun) for more than 30 years. Pyrotechnicians are specially trained in the use of fireworks. The company he works for, Pyrospectaculars, has been putting on fireworks shows for the Oakland A's for 20 years. The company has also created shows for Super Bowls and Olympic games.
Before the A's show, Thomas gives me a backstage tour. A parking lot behind the stadium has been closed off. Thomas and his team have set up rows of wooden frames full of thick plastic tubes. It looks more like a plumbing project than sky-high entertainment.
"This is the main aerial site," says Thomas. A smaller site is in a closed-off section at the top of the stadium. During the 18-minute show, about 500 fireworks shells will be fired. A large show like this one costs $30,000 to $40,000.
Thomas reaches into one of the tubes (called mortars) and feels around for the shell. "The first rule of safety is, never stick your face over a mortar," says Thomas. I'm expecting a rocket-shaped object, but he lifts out what looks like a ball covered in plain brown paper. When fired, this five-inch-diameter sphere, called a shell, will shoot 500 feet into the sky and burst into a brilliant green "chrysanthemum."
Nearby, steel tubes poke out of a sand-filled garbage can. The show's "big guns" launch here. Thomas pulls out a hefty paper-covered tube. "We call this one 'the salami,' " he says. "It is a multiple-stage shell. Because it is so big, we use a metal mortar instead of plastic."
Fireworks are carefully controlled chemical reactions. All fireworks use black powder (the modern name for gunpowder) to shoot them into the air. Black powder is usually made of potassium nitrate (saltpeter), charcoal, and sulfur. Each ingredient is stable on its own. But when combined to make black powder, a flame or electrical spark sets off a rearrangement of the molecules and atoms in these three ingredients. As this occurs, gas and heat are given off. The explosion pops the shell into the air.
All the fireworks have a fuse connected to an electronic "match." The match lights the "lifting charge" at the bottom of the shell.
The shell's fuse keeps burning even after the lifting charge shoots the shell into the sky. After a second or two - when the shell has reached the right height - the fuse ignites the black powder in the center of the shell. This is called the "bursting charge." Packed around the bursting charge are "stars" - balls or cubes with special chemicals that burn to give the firework its color, sparkle, or movement.
When the bursting charge explodes, it ignites the stars and flings them out in all directions. By packing the stars in different ways in the shell, a firework can be designed to look like a palm tree, a willow tree, a chrysanthemum, or a huge ring. The amazing aerial "smiley face" is the result of specially packed stars.
Some fireworks, like "the salami," have several stages. As one stage explodes, it lights the fuse of the next stage. The salami delivers three bursts of light in the sky over the stadium.
The hundreds of shells scattered across the parking lot are connected by wires to an electronic firing system. (I am very careful not to trip over any of the wires.) Thomas's control system seems simple - it's a laptop and a square silver box set on a table under a sunshade.