Fireworks

Sunset over New York. It’s July 4, one of the biggest dates in America’s calendar: Independence Day. Excitement fills the air. New Yorkers make their way to the dockside for a front-row seat of one of the biggest shows on Earth. The most gigantic firework display.

“All over the world people love fireworks. Nobody likes them more than the people in New York. We’re convinced of that.”

For days a team from Macy’s department store has been coordinating a massive operation involving engineers, TV crews, police and city and government officials.

“We deal with so many city agencies and so many people that work for those agencies, outside vendors, volunteers. All told there is about five thousand people that need to come together, be on the same page with us.”

A lot of effort for one of the biggest shows in the world. The vision of this man, firework designer Garry Sousa. “For me the first few aerial shells that go in the sky … I’m just totally thrilled … to me it’s the best moment in the whole show ‘cause then I know that things are gonna work.”

Sousa knows he’s only going to have one chance to get this right. By definition, you can’t rehearse a firework show. “Basically you get one shot at it and if it doesn’t work, basically – sucks.”

The Macy’s firework display will be one of the biggest and best ever. Yet no matter how high-tech it all seems even the most spectacular firework is the product of a very ancient technology. So how do they do it?

The story starts half the world away. In the Chinese city of Liuyang they know all there is to know about fireworks because fireworks is about all this town makes. Indeed fireworks are so central to the city’s way of life that they even put up a statue to honor them. One of Liuyang’s biggest employers is Black Cat. The company manufactures all sorts of fireworks, which produce the most exotic effects. But for all the modern packaging, the fireworks we use today remain the product of ancient techniques developed by the Chinese two thousand years ago here in the hills surrounding Liuyang. They still make fireworks in these hills. It’s too dangerous to do it anywhere else. And this is why. Black powder – the Chinese call it – a blend of charcoal, sulphur and potassium nitrate. By themselves, each of these chemicals is harmless enough. But once they’ve been mixed – look out!

The powder is mixed by day and it’s tested by night. Black powder was invented here 2000 years ago. But a match to it and it does this. The potassium nitrate in the mix acts as an oxidizer, in other words, when heated, it creates oxygen to make the other ingredients burn fiercely. But the ancient Chinese alchemists soon discovered something else interesting about black powder. When it’s packed into a confined space like a tube – kaboom! Pyrotechnicians call this effect the bursting charge. The ancients also learnt that if you make a hole in the bottom of a firecracker, you can direct the force of detonation downwards; you get what is now called a lifting charge, and that’s what makes a firework fly.

In the light of day manufacturing continues. But now we come to the most astonishing secret ingredient essential to making a firework. How do they turn simple rockets into amazing fireworks that perform all kinds of fancy tricks? How do they create the cascades, the clusters, the rings, the starbursts? The secret ingredient is rice. These pellets are filled with gunpowder. The Chinese call them pearls and they are made from dry rice husks, which have been coated with a slow-burning mix of powder and glue. The pearls stop the gunpowder from exploding all at once.

To get multiple effects pack the pearls into spheres called shells. To get different colors add different kinds of mineral salts. Strontium for red, barium for green. To get sparkle add flakes of aluminum. Link the shells to the main charge by time-delay fuses, light the rocket and you’ll set off a spectacular chain reaction: each wave of rice pellets ignited by the detonation of the previous wave. No matter how big or complex, all fireworks are based on this simple chain reaction effect. All you have to do is use more rice and different kinds of shells.

July 4, Manhattan. As darkness falls anticipation builds. It’s show time. Back at the control center, the countdown begins. In a few short moments the team here will unleash a barrage of high explosives across the city skyline. Quite suddenly, it begins. At a rate of a thousand shells a minute, the team launches a staggering forty thousand tons of high explosive into the sky. It’s a truly awesome spectacle. The technology may be 2000 years old but there is still nothing to beat the firework display.

“I love the fireworks the best. And there is something magical about them. This was the event that caused me to want to do events for the rest of my life.”

An amazing sight. And it all comes down to a bit of chemistry, a lot of rice, and a simple chain reaction. On July 4, thanks to Garry Sousa and his team and an age-old technology from China New York city celebrates American Independence with a bang.

Дата добавления: 2015-07-21