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 “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.