The Science Behind Your Favorite Fireworks

The Science Behind Your Favorite Fireworks

It takes a lot to create the extraordinary displays we enjoy on the different Occasions. Sometimes, the staging alone can take hours of planning for a few minutes worth of display—it takes even longer when a show is set to music. And fireworks aren’t cheap.

The July Fourth Boston Pops Fireworks Spectacular costs in excess of $2.5 million. Shorter, simpler shows like what you’d find in a small town can run between $2,000 and $7,000. The use of larger shells bursting in synchronization with music can cost around $2,000 a minute, putting a 20-minute display at $40,000.

Inside a Shell

Here is a 6-inch cylindrical shell. The time delay fuse is at the far left; square stars are in the left compartments; and the bursting charge extends through from the fuse to the black lift powder at right.

What Gives Them Color?

If fireworks were strictly gunpowder, there’d be no excitement, really. They’d all just be balls of fire in the air.

Salts and other metal compounds allow a firework to detonate in bursts of bright blue or rich red. To make red, fireworks contain strontium salts and/or lithium salts, with the strontium producing a brighter red reaction. Calcium salts make orange, while sodium salts (as in table salt) explode in yellow. Green comes from the compound barium chloride, blue from copper chloride.

Silver or white colors are made of aluminum or magnesium. If you want purple, you have to work a little harder: Combine strontium salts for red and copper chloride for blue to create a purple explosion.

Sparklers

Because sparklers are governed under the same laws as fireworks, we’ll include them even though they’re technically considered novelties.

Sparklers consist of several compounds that when mixed, create a slurry into which the body of the sparkler is dipped. This coating is what burns and produces the bright light that sparklers emit. The fuel and oxidizer are added in specific proportions so that the sparkler doesn’t explode like a traditional firework, but instead burns much more slowly (and safely).

Spider man

The guts of this firework must be carefully placed into a cylindrical shell about the size of a Quaker Oats canister, Souza says. In the center of the shell are tiny round green stars that burst as a teal peony at the firework’s nucleus.

Larger gold comet stars border the teal pellets and flare out when ignited, eventually peeling off into sharp scarlet quills. The animation can be changed by inserting scarlet stars into special compartments at the outskirts of cylinder.

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