Staring up as cascades of colorful light bloom noisily from the dark sky—that's how many Americans will conclude their Independence Day. Behind the pretty image, however, fireworks rely on basic physical and chemical principles. So just how do fireworks work? Various corners of the internet, including this website, have tackled the topic before.

In 2003, Scientific American published "What are the physical and chemical changes that occur in fireworks?", an Ask the Experts feature by University of Missouri at Rolla professor Paul Nicholas Worsey.

The most common type of display firework is the aerial shell, which is fired from a mortar tube. These fireworks typically have four components: a lift charge, a time-delay fuse, a breaking charge and a light/effect generator. The lift charge is generally black powder, a compound that burns rapidly and propels the shell from its tube. The lift charge also ignites the delay fuse when it fires. The delay fuse is usually a black powder fuse with a delay of a few seconds, and it is designed to ignite the break charge when the shell reaches the appropriate height. The purpose of the break charge, which sits at the center of the lofted shell, is to explode, thereby igniting and scattering the shell's contents. This break charge is generally finer-grained black powder than the lift charge and more highly confined, which causes the shell to explode. The payload of the shell usually comprises small spherical pellets of pyrotechnic composition designed to generate light.