How Do Fireworks Work?

There's a lot going on behind those pretty colors!

Fireworks can be a little perplexing when you think about it. They blow up and go boom, but their purpose is solely for fun and entertainment! And most Americans would undoubtedly say that it’s not Independence Day without a fireworks show, like one of these best fireworks displays in every state.

But if, in between oohing and ahhing at beautiful fireworks displays, you’ve found yourself wondering, “How do fireworks work?” you’re not alone. Learning about the chemistry of fireworks, and how they’re able to do what they do, makes them that much more impressive.

What are fireworks made of?

They’re called “fire” works, but it’s not quite as simple as just plain fire. It’s actually “a controlled explosion releasing the energy through heat, light, and sound by a cascade of chemical reactions,” explains Jon Kirchhoff, chair of The University of Toledo Department of Chemistry and Biochemistry. That might sound complicated, but the materials themselves are actually pretty simple. It’s the way they combine that results in the awe-inducing show we’re familiar with.

Per Dr. Lawrence Anderson-Huang, professor emeritus of physics and astronomy at The University of Toledo, the materials that make up fireworks are: “A mortar cannon filled with black gunpowder;…a bursting charge, also of gunpowder, wrapped in a paper container; so-called ‘stars’ embedded in the bursting charge; and fuses to set the charges off.” As for the gunpowder itself, that’s made up of charcoal, sulfur, and potassium nitrate, which is an oxidizer.

So how do fireworks work, exactly? How do those components produce such dazzling results?

How do fireworks work?

The chemistry of fireworks begins when someone lights the primary fuse, which ignites the gunpowder. Now the chemistry of fireworks can begin. Lighting the fuse starts a combustion reaction with the gunpowder and the oxidized potassium nitrate. “The resulting reaction products or exhaust gases supply the force to counter gravity and send the rocket skyward,” Kirchhoff told Reader’s Digest. If the components are reacting like crazy, why don’t they explode immediately? Well, as Anderson-Huang explains, “A slower fuse…delays the explosion of the bursting charge until it has reached the proper altitude.” Now that you know how fireworks work, find out why we set off fireworks in the first place.

Where do the colors and patterns come from?

And now for the fun part! Before the fireworks explode at their proper altitude, viewers can only guess what colors and patterns will appear. That’s where the “stars” that Dr. Anderson-Huang describes come into play. The stars, which are “pea-sized spheres or cubes,” contain black gunpowder and flakes made of slow-burning substances like aluminum and zinc. When the stars ignite in the bursting charge, “This secondary explosion burns the metals by the intense heat produced and sends bright colors outward in beautifully colored symmetrical patterns that light the sky,” says Kirchhoff. The various placements of these “stars” in the bursting charge create the different patterns we see, and different combinations of metals and chemicals, like copper (blue), sodium (yellow), and strontium (red), produce the full range of colors.

So, now that you know how fireworks work, sit back, relax, and enjoy this Independence Day. Or, if you’re still curious, read on to find out 13 more fascinating things you never knew about fireworks.

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Meghan Jones
Meghan Jones is a Staff Writer for RD.com who has been writing since before she could write. She graduated from Marist College with a Bachelor of Arts in English and has been writing for Reader's Digest since 2017. In spring 2017, her creative nonfiction piece "Anticipation" was published in Angles literary magazine. She is a proud Hufflepuff and member of Team Cap.