Boise & Garden City

Red, white and pale blue! Science explains the magic of Fourth of July fireworks.

The chemistry of fireworks

A chemistry lesson on fireworks and what makes them different colors.
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A chemistry lesson on fireworks and what makes them different colors.

On the Fourth of July, bright and beautiful fireworks will fill the evening skies in Boise and across the nation. Behind every “ohh” and “ahh” is a careful combination of chemicals, fuels and creativity.

Not to mention a little mystery, like why we have to settle for pale blue in our red, white and blue displays.

A deep, dark blue has evaded pyrotechnicians for hundreds of years.

“Our biggest challenge is blue. A pale blue is the best we can do,” John Conklig said in an interview with the Idaho Statesman. “Copper does cooperate to emit a strong blue light, but it pales in brightness compared to red and white. People have been trying for centuries to get a deep blue.”

Conklig is a retired pyrotechnic chemistry professor at Washington College and former executive director of the American Pyrotechnic Association.

Creating brilliant fireworks displays involves selecting the right ingredients and packing them to produce the desired effects.

“It is all chemistry, and a little bit of physics,” Conklig said.

According to Conklig, fireworks are packed with careful combinations of chemicals to ensure the firework explodes at the right time and shines bright in the sky. Mixing aluminum or magnesium with the fuel increases the temperature to achieve brighter colors. A starch or water binder holds the firework together so that it explodes correctly in the sky. And the metal salt is the colorful star of the fireworks.

“You need a chemical mixture that contains an oxygen-rich chemical and a fuel that can combine to get a good fire, then to that fire you add specific chemical elements in the presence of high temps that emit light to disperse energy,” Conklig said. “Light emitted depends on the element. The specific wavelength picked up by the human eye perceives a specific color.”

Chemistry of Fireworks
Different colored fireworks are made by adding different colored chemical elements. Kate Talerico

Pyrotechnicans add different metal salts to create colors.

  • Red is from strontium.

  • Light blue is from copper.

  • Green is from barium and boron. Barium is the traditional way, but boron is a newer, less toxic and more environmentally friendly green.

  • White is aluminum.

  • Yellow is sodium.

  • Orange is calcium.

Other colors are made by mixing different chemical elements. Silver, for example, is made by mixing aluminum and magnesium, or purple is made by mixing strontium and copper.

Effects like flashes and spirals require more planning with the colorful metal salt.

“There’s lots of testing to get a new effect for color, intensity and safety,” Conklig said. “Flash fireworks have a looser-packed composition so the flame is quicker and more energetic. Powder can be pressed into spirals in the tube. The tube can be different shapes to create different shapes of fireworks, and the spiral packing causes the tube to spin and move.”

A science lesson explains the magic behind the annual fireworks show at Ann Morrison Park. Idaho Statesman file photo

The Fourth of July is the most American holiday, but most fireworks set off on that day are not American-made.

“Almost no fireworks are manufactured in the U.S. anymore. Only 5% are,” Heather Gobet, owner of Western Display Fireworks, said in an interview with the Statesman. Western Display Fireworks is the Oregon-based, fourth-generation pyrotechnic production company that designs Boise’s fireworks show.

The high cost of labor and strict regulatory pressures to safely manufacture fireworks make them too costly for many American manufacturers.

“Fifty years ago, fireworks displays would be largely U.S. products, but China has become the leading fireworks manufacturer,” Conklig said. “Labor costs are lower in China, regulatory costs to comply with the requirements for safety are not as stringent .... so Chinese fireworks sell for a lower price.”

Boise’s annual Fourth of July Fireworks Celebration will take place in Ann Morrison Park. The event is free to the public, and the fireworks display starts at 10:15pm.

“We do over 200 shows on the 4th, and Boise is one of my personal favorites,” Gobet said. “The venue is beautiful and the choreographed show is stunning.”

Other fireworks shows are planned in Melba, Star, Caldwell (Brothers Park) and Meridian (Storey Park) — and at the Boise Hawks game at Memorial Stadium.

Rachel Hager is writing for the Idaho Statesman this summer on a fellowship through the American Association for the Advancement of Science. She is a master’s student in ecology at Utah State University and earned a bachelor’s degree in biology at Bryn Mawr College.