Tonight, as the sky bursts into glorious spheres of color, many a child will turn to their parent and ask, “How do they do that?” And many a parent will consider faking an answer about pixie dust or exploding trolls. But fret no more!
Marshall Brain, the founder of the Web site http://people.howstuffworks.com" class="content-link" target= "171">“How Stuff Works” demystifies things that go BOOM! in the night.
Q: Are firecrackers and aerial fireworks all that different?
A: No. When an aerial shell explodes, there’s a big firecracker inside it making that possible. The shell is placed atop a lifting charge, another type of firecracker, that launches it in the first place.
Q: So, aerial fireworks are basically firecrackers packed with extra features that rise before they explode?
A: Right. Almost every kind of fireworks begins with black powder. Aerial charges are usually lit by an electronic fuse and fired out of a tube. The lifting charge gets it into the sky. The bursting charge, in the center, is often lit at the same time. But it has a longer fuse.
Q: What happens when the bursting charge blows it apart?
A: That depends on what’s inside the shell. All around the bursting charge, packed in black powder, are other firecrackers, or stars. The crackling you hear when a shell explodes is other firecrackers detonated by the black powder. The bursts of light are stars.
Q: What’s in a star?
A: Stars are made of sparkler material — filings of iron or aluminum — that shower sparks as they burn. They are mixed with a binder material, like starch, that slows down the burn process so it doesn’t all go off at once. For sparklers, the mixture is coated on a wire. For stars, they roll it into balls, the size of a pea or a dime, and let them dry.
Q: Then they pack them into the aerial firework?
A: Right. Typically, in the U.S., you’d put the stars into a cardboard cylinder. That would be your shell. Then, pour black powder all around them to help them ignite. Then, a firecracker goes in the center, which would be your bursting charge.
Q: How do they get different colors?
A: Different chemical compounds. You get blues with copper compounds, yellows with sodium compounds, orange with pure carbon. The prismatic effect, when colors change, usually comes from a core star, dipped in layers of various compounds. As a star blows out, it burns through the different layers of colors.
Q: It sounds like fireworks composition is a very precise science.
A: Oh, yeah. Lots of care goes into the patterns. A lot of what we see has come from China, which has been making these for hundreds or thousands of years.
Q: Thanks for explaining this. You’ve given lots of parents something to tell their kids tonight.
A: It’s perfect when that happens.