Fantastic Fireworks: The science of colors and bangs

Independence Day fireworks in San Diego, California

Hopefully you had a chance this month to be dazzled by some amazing fireworks!  Did you know that fireworks are chemical reactions?  There are a lot of different kinds of fireworks.

Here's how one of the most popular kinds of fireworks works.  To set off a firework, you light a fuse.  The heat from the flame travels along the fuse, until it reaches the bottom of the main part of the firework (shell).  When it reaches this point, it ignites a lift charge, which is made out of black powder.  When the heat touches the black powder, it creates hot gases and lots of energy! These forces launch the shell out of the tube it is sitting in (called a mortar).  The shell is full of small pellets.  Once the firework reaches a certain height, a second fuse inside of it ignites and activates a burst charge.  This sets off the pellets, which explode into colors and sounds.

What the explosion from a firework looks like depends on the chemicals inside of the pellets.  Some fireworks contain metal salts, which create bright colors.  Here are the metal salts used and the colors they produce:

Strontium: Red
Calcium: Orange
Sodium: Yellow
Barium: Green
Copper: Blue (This is one of the hardest colors to create in a firework.  For more on this, check out this article.)
Strontium and Copper: Purple
Magnesium, Aluminum, and Titanium: White

Some fireworks have chemical compounds that cause effects like sparkling or strobing lights.  Some even use different chemicals to create sound effects!  For instance, bismuth makes a crackling or popping sound, while potassium chlorate creates a loud boom.

Fireworks can be awesome, but because of the high heats and explosions involved in setting them off, they are also very dangerous!  Unfortunately, sometimes things do go wrong and people get hurt.  Always make sure that you are following proper fire safety measures when you are setting off fireworks at home.  Put enough distance between yourself and a lit firework, never relight a firework that didn't go off, keep flammable liquids away, and have a bucket of water nearby in case of an emergency.  Be safe and enjoy your chemical reactions!

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