Engineers Celebrate the 4th of July with a Bang!

As the sun drops behind the horizon and the evening light fades from the sky on the 4th of July, millions of people all across the country prepare for a show. What’s more American than blowing things up in celebration of a peace treaty?

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While most spectators are “Oohing” and “Aahing” from their folding chairs, some may find themselves thinking, “I wonder how that works.” As it does more often than not, the answer lies in engineering.

A firework is composed of two main components; explosives and stars. Stars are combustible, colorful pellets that glow as dots when the firework explodes. A pouch of gunpowder, called the ‘lifting charge’ is fired from the base of the shell, propelling it out of the mortar tube. As the shell is fired, a delay fuse is lit within the firework, giving it the necessary time to reach the desired height. At this point, another gunpowder pocket at the center of the shell, known as the bursting charge, will explode, sending the colorful stars flying in all directions.

The shape of the firework is determined by placing the star pellets in specific patterns within the bursting charge. Precise positioning will result in the explosion propelling the stars into the desired shape.

The colors of the firework are the product of chemical engineering. Red fireworks are usually made using strontium or lithium, green fireworks are made from barium, yellow from sodium, white from magnesium, orange from calcium, and blue fireworks are made from chlorine compounds and copper. Fireworks that change color are made by layering the coating of the star; the outside burns first and inward. Adding titanium to the coating creates a sparkling effect and magnesium perchlorate gives fireworks the loud cracking noise.

Now every time you’re sitting back and watching a firework display, you can thank a team of engineers for filling you with a sense of childlike wonder and amazement.