Put simply, fireworks are awesome. The sounds and smells of the explosions, the bright colors, the audience’s collective rapture—it’s all enchanting. But what’s most impressive is the combination of power and precision. These giant exploding fireballs are actually the result of delicate chemistry that’s more like an art than anything else.
The foundation of any firework is black powder, which is a mixture of oxidizing agents and fuel. Combustion reactions require a lot of oxygen, so oxygen-rich chemicals such as potassium nitrate or potassium perchlorate are crucial players in the powder. Combinations of sulfur, charcoal, aluminum powder, and magnesium powder engineered to optimize the burning rate and heat output serve as fuel. These combine with the oxidizer to produce the heat that catalyzes a complicated combustion reaction (really multiple reactions in one). The important thing, though, is that the combination produces lots of gas in a little bit of time, a thermodynamically favorable reaction that results in a dynamic show of released energy.
But explosions by themselves are not enough for fireworks—pyrotechnicians need to maintain some sort of control. This comes in the form of a binder, an organic compound such as dextrin. The binder glues all the components of the firework together, keeps it relatively stable, and allows pyrotechnicians to time the explosions to their likings. Fuses are crucial for timing and are often electrical, controlling the entire firework show with one click from a computer.
Nevertheless, explosions, even those meticulously controlled by computers, aren’t exciting enough—they need color, sparkle and shape to be worthy of a show. These are all the results of metal salts. Each combination of salts will release light with a very specific wavelength depending on their energy levels and electron distribution, allowing for the rainbow of fireworks. For example, strontium salts produce red, calcium salts orange, sodium salts yellow, barium salts green, copper salts blue, and strontium and copper combined produce purple. Don’t forget the sparkles! Coarse magnesium provides the sizzling sparkle effect. The salts and metals in the form of little pellets aptly called “stars” are placed strategically inside a firework’s aerial shell, resembling the pearls in bubble tea. Additional fuels are also packed with them to help augment their specific patterns and shapes.
Frankly, it doesn’t require much chemical prowess to create an explosion. Anyone who has seen Looney Tunes can attest to that. But fireworks are more than an explosion– they’re a large-scale demonstration of the intricacies of chemistry. After all, chemistry isn’t just a study of the tiny particles we can’t see; it’s also an exploration of the most massive displays of chemical grandeur.
Sources:
“The Chemistry of Fireworks.” Reactions, YouTube, 30 July 2014, www.youtube.com/watch?v=nPHegSulI_M.
Brockmeir, Erica. “The Chemistry behind Fireworks.” Penn Today, 1 July 2019, https://penntoday.upenn.edu/news/chemistry-behind-fireworks.
“The Chemistry of Fireworks.” Compound Chem, 30 December 2013, https://www.compoundchem.com/2013/12/30/the-chemistry-of-fireworks/.
“How do Fireworks work?” Concerning Reality, YouTube, 8 May 2019, https://www.youtube.com/watch?v=n1ixjhzwr_E.
“Chemistry Compounds.” Phantom Fireworks, 2021, https://fireworks.com/education-and-safety/chemistry-compounds.
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