How do fireworks work?

Answer 1

Just about everyone in the United States has some personal experience with fireworks, either from Fourth of July or New Year’s Eve celebrations. For example, you have probably seen both sparklers and firecrackers. It turns out that if you understand these two pyrotechnic devices, then you are well on your way to understanding aerial fireworks. The sparkler demonstrates how to get bright, sparkling light from a firework, and the firecracker shows how to create an explosion.




Firecrackers have been around for hundreds of years. They consist of either black powder (also known as gunpowder) or flash powder in a tight paper tube with a fuse to light the powder. Black powder, discussed briefly in How Rocket Engines Work, contains charcoal, sulfur and potassium nitrate. A composition used in a firecracker might have aluminum instead of or in addition to charcoal in order to brighten the explosion.

Sparklers are very different from firecrackers. A sparkler burns over a long period of time (up to a minute) and produces extremely bright and showery light. Sparklers are often referred to as "snowball sparklers" because of the ball of sparks that surrounds the burning portion of the sparkler. If you look at Patent #3,862,865: Sparkler composition, you can see that a sparkler consists of several different compounds:

A fuel
An oxidizer
Iron or steel powder
A binder



See this Question of the Day for a discussion of oxidizers -- potassium nitrate is a very common one. The fuel is charcoal and sulfur, as in black powder. The binder can be sugar or starch. Mixed with water, these chemicals form a slurry that can be coated on a wire (by dipping) or poured into a tube. Once it dries, you have a sparkler. When you light it, the sparkler burns from one end to the other (like a cigarette). The fuel and oxidizer are proportioned, along with the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker.

It is very common for fireworks to contain aluminum, iron, steel, zinc or magnesium dust in order to create bright, shimmering sparks. The metal flakes heat up until they are incandescent and shine brightly or, at a high enough temperature, actually burn. A variety of chemicals can be added to create colors.

In the next section, we'll look at aerial fireworks, such as those you might see in a fireworks display.

Answer 2

gun powder

Answer 3

light them - they go bang