Jun
28
2007

Chemistry in the sky: The science behind fireworks

Bursting with science: When you watch fireworks this holiday season, take a second to think of all the science shooting out over you in the night sky.
Bursting with science: When you watch fireworks this holiday season, take a second to think of all the science shooting out over you in the night sky.
Working at the Science Museum of Minnesota today, I occasionally had the chance to watch work crews across the street prepare for the six days of fireworks that will be shot off for the Taste of Minnesota celebration that runs Friday through the Fourth of July. It got me wondering more specifically about the science involved with fireworks.

So I’ve “googled” around the Internet a bit today. Read this and impress all your fireworks watching friends over the coming holiday with your amazing new-found knowledge on the science of fireworks.

DISCLAIMER: Do not use any of this information to create your own fireworks. We want to keep you reading Science Buzz for a lot longer into the future.

Most of us have played around with firecrackers or sparklers at some time. There’s a lot to be learned from those simple, basic fireworks to understand how the big, high, colorful fireworks work. On a much smaller scale, a sparkler creates the vivid light and color that we find in fireworks; a firecracker demonstrates how to create an explosion that can lead to the release of that light.

Inside of firecracker is black powder or flash powder that ignites quickly with fire. Some firecrackers have aluminum added to the powder to create a brighter flash at the time of the explosion.

Sparklers, on the other hand, burn much slower but have incredibly bright light. Their ingredients include a fuel, oxidizer, iron or steel powder and a binder. The fuel is often charcoal or sulfur (hence the nasty smells sometimes), the oxidizer is often potassium nitrate and the binders are sugars or starch. For a sparkler, all those ingredients are mixed with water, coated on a wire and then dried before being ready to ignite.

These two principles are combined into the larger form of fireworks. For the big aerial bombs we love to watch, different chemical compounds – aluminum, iron, steel, zinc or magnesium -- are used to create the different colors.

Once the chemicals are delivered high in the sky and the firework is exploded, the metal flakes that shoot out from it heat up and become the different colors we see. Gravity quickly takes over and pulls those flakes back down to Earth, giving us the usual fireworks effect.

Shell game: These is the typical packaging for fireworks shells. Inside is a mix of explosives and chemicals that when lit up give us the spectacular effects.
Shell game: These is the typical packaging for fireworks shells. Inside is a mix of explosives and chemicals that when lit up give us the spectacular effects.
To get those fireworks up in the sky, we turn to some rocketry science. Aerial fireworks commonly are put into a shell. It can range from something simple like a paper tube to more complicated wood-case balls.

Inside the shell are the stars, the chemical materials that will ignite in the sky and turn to the pretty colors. At the bottom of the shell is a lifting charge, which powers the shell up into the sky when ignited. Inside the shell is a bursting charge, which is connected to a fuse that burns slowly as the shell goes into the sky and eventually fires a bursting charge. That charge blows apart the shell and starts the fireworks mayhem.

Things just can get more complicated after that. Multi-break fireworks can contain different combinations of stars, different inner shells that might ignite at different times, creating even more spectacular effects.

Your Comments, Thoughts, Questions, Ideas

Gene's picture
Gene says:

Popular Mechanics has an article on the science of fireworks. As well as some tips for doing the Fourth of July right.

posted on Wed, 07/04/2007 - 8:24am
Anonymous's picture
Anonymous says:

how do they get the fireworks to make many different shapes?

posted on Wed, 07/04/2007 - 11:42am

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