How Do Fireworks Work?
The 4th of July falls on a Wednesday this year, a bit out of sync for my typical organization of posting health-related information on Wednesdays and science on the weekends but alas, I do not control time. So let’s get down to it: (1) Who even decided fireworks were how to celebrate properly? (2) How do fireworks work and why do we see all these different colors and designs in the sky? (3) And what is the environmental impact of fireworks?
The History of Fireworks
Fireworks have been around for roughly 1000 years. The first documented firework was created by the Chinese in the form of a “fire pill,” which was essentially a fire cracker (gunpowder wrapped in paper). But rather than using it as celebration, they used it to ward of evil spirits.1 .They also used them for ceremonies and festivals for the Emperor (however still with the thought that they warded off ghosts and evil spirits, thus allowing for greater happiness and good luck). In the 1600’s, fireworks became more westernized (as many things do…) and they were popularized by European military and used for celebrations — but they still weren’t what we think of today. At this point, fireworks were still only a single color: orange.2So when did it become what we know today? The modern firework dates back to the 1800’s.
But why do we use them on the 4th of July? Well, we can thank the British for that. English royals were so jazzed about fireworks that they went out of their way to introduce them to literally everyone else. (King James II’s pyrotechnician was awarded knighthood for his work, they were real serious about their fireworks.2) So on the very first celebration of the 4th of July, in 1776, they decided that the date had high significance and started the tradition and here we are today, still celebrating it the same (but far fancier) way. Thanks John Adams.3(We’ll just ignore the fact that the Declaration of Independence wasn’t fully signed off on by July 4th but that’s irrelevant now…)
How Do Fireworks Work
When we think of fireworks today, we think of spectacular pyrotechnic shows. The science behind these firework displays is not simple.4 First of all, it takes a myriad of chemicals to create the colors and effects that we see. But what’s really impressive are the patterns!
Current fireworks use a multi-break shell system so that when the shells are ignited the explosions occur at different times, essentially they are on a time release system that is based on the speed of fire. The way that the explosives are packed within the shell dictate the way they will look in the sky — for example, if they pack in the shape of a smiling face, then that’s what you’ll see in the sky when that layer is ignited!5
But why don’t they just explode on the ground? Fireworks used for these spectacular displays are little rockets. They are created in order to be propelled into the sky before explosions occur. To better understand, let’s break down the anatomy of the firework rocket on the right:6
The stick is utilized for directionality. It also helps with positioning fireworks for the entire show.
The fuse is the ignition point (where the fire is). This where the burning begins.
The charge (not shown) is somewhere between the ignition point and the body. It is the part that contains the necessary combination to propel the firework into the air. The usual composition is 75% potassium nitrate, 15% charcoal, and 10% sulfur.
The body is where the effects and the multi-break shell is! Once in the air, this is where the fun and spectacle comes from!
The head has a pointed shape for aerodynamics and directionality.
Fun fact: The boom sound is not from ignition but actually from perchlorate!
The Environmental Impact of Fireworks
Noise. This one is quite obvious, fireworks emit a large *bang* sound since they are explosives. This can be damaging to anyone with sensitive hearing or even regular hearing depending on distance from display sourse.
Smoke, Particulates, and Water. The smoke that is left behind is highly concentrated with various metal particulates which are scattered through the air, particularly potassium and aluminum compounds. This leads to air pollution and is technically a toxin for us to inhale. The color that fireworks now have adds an addition chemical off put into the air as well: copper from blue, strontium or lithium form red, and barium from green and white. Many firework shows occur over large bodies of water, so not only do these particulates and dust get into the air but they also fall to the water, causing metallic contamination.
The Future. These are beautiful yet toxic displays that people gather to watch together. What can we do about this? Well, Disney claims that they’ve developed a new technology that replaces gunpowder with compressed air, effectively removing one of the major pollutants of firework displays.7 This is a major win for places such as theme parks that have constant firework displays! All we can hope is that this expands beyond just theme parks and into regular use to help offset the pollution a bit so we can continue to watch these magnificent pyrotechnic shows!
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1. Lidu Fireworks. CCTV. 23 Sept 2004.
2. Stempien A. The Evolution of Fireworks. Smithsonian: Science Education Center. 01 July 2016.
3. Cohen J. Fireworks’ Vibrant History. History. 01 July 2011.
4. Earth Talk. Declare Your Independence from Toxic Fireworks Pollution. ThoughtCo. 17 March 2017.
5. Wells S. The Science Behind Fireworks — How Do They Produce The Brilliant Colors and Designs? Steve Spangler Science. 26 June 2013.
6. Woodford C. Firework science. ExplainThatStuff. 14 Jan 2018
7. The Business Journal. The future of theme park fireworks: Disney embraces smoke-free pyrotechnics. NBC News. 13 July 2004.
Originally published at klattalyst.com on July 4, 2018.
