Image credit: Wikimedia Commons user Draper, of fireworks in Prescott Valley, AZ.

The Physics of Fireworks

After 4th of July this past Monday, here’s the science behind how they work!

“Celebrate the independence of your nation by blowing up a small part of it.” -The Simpsons

This past Monday marked the 240th anniversary of the United States’ independence from Britain, which is celebrated all across the country with tremendous displays of fireworks. From individual hobbyists to professional installations, fireworks all have the same physics behind them and the same four component stages: the launch, the fuse, the burst charge and the individual stars. Get it wrong, and you could be facing anything from a sub-optimal display to a dud to a dangerous fire hazard. But get it right, and the most spectacular shows of all are yours to behold.

The three main ingredients in black powder (gunpowder) are charcoal (activated carbon), sulfur and potassium nitrate. Image credit: Wikimedia Commons user Ravedave under c.c.-by-2.5 (for the carbon); public domain photos for the sulfur and potassium nitrate.

You start with three simple ingredients: sulfur, charcoal, and a source of potassium nitrate. Charcoal, in this case, is not the briquettes you use on your grill, which often contain no actual charcoal, but is the carbon residue left behind by organic matter (like wood) once it has been charred (or pyrolyzed), having had all the water removed. Potassium nitrate is found in sources like bird droppings or bat…