Science While You Ooh and Aah

July 3, 2007

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In between the "oohing" and "ahhing" directed towards the brilliant colors, dramatic patterns and bombastic sounds of this week's July Fourth fireworks displays, you might take a moment to admire the impressive manufacture numbers and awesome display of chemistry and physics, too.

Today China is the largest manufacturer and exporter of fireworks in the world, estimated to have exported more than 6 million cases, or 120,000 tons, of fireworks to the United States in 2005," according to Wikipedia.

The value of fireworks imported from China last year: $206.3 million, representing the bulk of all U.S. fireworks imported ($216 million), according to the United States Census Bureau.

Although the Chinese produce the lion's share of fireworks, some are made domestically.

For example, a report from American manufacturer Zambelli Fireworks notes that the Nashua Harbor Plant, located on a 400-acre hillside secluded outside New Castle, Penn., has more than 60 blockhouses for manufacturing and storing fireworks. Another plant specializes in manufacturing aerial shell components, which are then transported to the Nashua Harbor plant for completion, according to Zambelli.

U.S. exports of fireworks came to $22.6 million in 2006, with Japan purchasing more than any other country ($8 million), according to foreign trade statistics from the Census Bureau.

There really hasn't been much dispute that China leads when it comes to fireworks, or that they originated in China. Yet as you "ooh" and "aah" at the dazzling explosions of a fireworks display tomorrow, there are a few things going on that you might not guess, says MSNBC:

The chemists who made those pyrotechnics designed most of them so they wouldn't explode; you're actually seeing nature conserving energy; and most peculiar of all, when things are at their flashiest, you're actually seeing the fireworks as they're cooling down.

According to LiveScience, the handmade firework shell contains "a powdery concoction of chemicals that produce the bangs and the whistles, as well as the pretty effects." Tubes, hollow spheres and paper wrappings work as barriers in the device, while complicated shells are divided into even more sections to control the timing of secondary explosions once the rocket is airborne.

Once used for flashes in photography, flash powder — a combination of fuel-like metal and a chemical that feeds oxygen to fire up the fuel — provides the "big booms and whistles."

The variety of color in a fireworks show depends on the mix of metals: copper for blue sparks; barium makes green; calcium burns orange; sodium makes yellow; and aluminum and titanium put the white stars in an aerial flag. Purple results from a mixture of strontium and copper compounds; charcoal or lampblack produces gold and burning titanium, aluminum or magnesium powder or flakes creates silver.

To light up a specific pattern or design — such as a red, white and blue flag — chemists lay out the emblem's design on wax paper. Whatever pattern you see up in the air mirrors the arrangement of the metals in the shell.

As for the array of sounds, different combinations of metals and oxides are at work.

LiveScience reports:

While ancient Greeks and Romans used bismuth in their beauty care products and coins, chemists add bismuth trioxide to the flash powder to get that crackling sound, oddly named "dragon eggs." Ear-splitting whistles take four ingredients, including a food preservative and Vaseline.

What Makes 'Em Go Generally, black powder is used as a propellant to shoot flaming balls, and in the manufacture of stars for aerial effects, according to Fireworks Glossary. "Black powder is a mixture of potassium nitrate, charcoal, and sulfur. It is the principal ingredient in most fireworks because it is not sensitive to shock and its burning properties are predictable and slow."

Historically, fuses allow for a delay in detonation to give the fireworks enough time to ascend into the sky so a crowd can view them. "Used in the manufacture of fireworks, black match is a type of fuse that is made by saturating cotton string in black powder. Unconfined, black match burns at an approximate rate of one inch per second," according to the Fireworks Glossary.

As with many devices, electronics and fireworks have joined to make these events safer and less smelly.

"In 2004, Disneyland in Anaheim, Calif., started using aerial fireworks launched with compressed air rather than gunpowder, the first time that such a launch system was used commercially," according to Wikipedia. The display shell explodes in the air using an electronic timer. The advantages of compressed air launch are a reduction in fumes, and much greater accuracy in height and timing.

Flash Powder forms the explosive component of firecrackers, aerial salutes, and the reports in rockets and roman candles. This silvery chemical mixture usually consists of potassium perchlorate and finely powdered aluminum. Flash powder is very dangerous to manufacture, according to the Glossary.

Nevertheless, safety remains a concern. More than 6,000 children go to emergency rooms every year for at-home fireworks-related injuries in the United States, according to study released this time last year (via LiveScience). Parents are present in more than half the cases, say researchers at the Center for Injury Research and Policy at Columbus Children's Hospital in Ohio.

If you're sitting around biding your time at the computer before tomorrow's festivities (or tonight's pre-party), check out fellow blogger David's Fourth of July: By the Numbers today for some impressive numbers and fun facts relating to celebratory cookouts, Independence Day travel, barbecue safety and the renowned Nathan's Famous International Hot Dog Eating Contest.

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