Colors of the celebration

Festive fireworks and bridge lights reflect in the Arkansas River at Little Rock. (Linda Henderson photo)

by Linda Henderson

You can’t say Fourth of July without thoughts of fireworks. The celebration brings the sights of red, orange, yellow, green and blue fire blasting into the hot and humid Arkansas sky. The sound of exploding colored charges brings “ohhhs” and “ahhhs” from crowds gathered around. But what causes those beautiful colors?

The Science Nerd and college chemistry minor in me wants to know where the colors come from. The simple answer I found was chemistry. The colors in fireworks are created by adding metal salts to black powder. Fireworks are basically small rockets designed to explode in a very controlled way. The explosion renders bursts of brightly colored light or pellets called stars.  

Metal salts commonly used in firework displays include: strontium carbonate for red fireworks, calcium chloride for orange fireworks, sodium nitrate for yellow, barium chloride for green, and copper chloride for blue fireworks. After a firework is ignited, there is an explosion of black powder in a confined space that causes a fast increase in heat and gas that lifts the firework into the sky. A time-delayed fuse slowly burns into the firework shell and after about 5 seconds, the core is kindled and the metal salts are released in a beautiful fiery display.  

Fireworks have been around for a very long time. They were likely invented in China during the 6th century. During the 13th century, Europeans started to use them as a way to celebrate national events.  They became popular in the United States during the 18th century as a way of celebrating Independence Day. The first use of fireworks to celebrate Independence Day was recorded in the Pennsylvania Evening Post in 1777. “The evening was closed with the ringing of bells, and with a grand exhibition of fireworks.”  

So, on this July 4th, let the tradition of lighting the sky with patriotic colors and the sound of exploding rockets, firecrackers, sparklers and spinning pinwheels continue. I will now, not only appreciate the bright colors and festivities, but also the science of fireworks.

Linda Henderson
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