How Fireworks Produce Color

This article was first published last July, 2010, but after colleague Kelly retweeted it today, I thought, "great idea! Let's bring it back for this year."

With 4th of July just around the corner, we're all intent upon nailing down the best spot for the most impressive fireworks display. (FYI- I have heard Boston's show is amazing)

But how do we get all those amazing colors in every burst of light?

A little background...Visible light of different wavelengths is detected by our eyes as a range of colors. Of the light that we can see, violet has the shortest wavelength and red has the longest.

Wavelengths of light corresponding to different colors

Fireworks generate light and color due to the physical and chemical attributes of specific compounds. When these compounds are heated and combusted they give out energy, some of which may coincide with the wavelengths in the visual region of the spectrum.
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The mixture of specific chemicals can produce different colored fire. 
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To make fireworks colorful, metal salts are added to the basic oxidant fuel mix concoction. For example, if you put a piece of copper into a fire you see it glow with a blue flame.
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The amount of energy released, which varies from element to element, is characterized by a particular wavelength of light.
  • Strontium or carbonate salts (longest wavelength and lower energies) = red flame
  • Copper oxychloride (much shorter wavelength and higher energies) = blue flame
  • Barium nitrate = green flame
  • sodium salts = yellow flame
  • charcoal or other forms of carbon = orange flame
With those metal salts, pyrotechnicians have a whole spectrum of colors at their disposal. If no salts were added, the fireworks would simply reflect all the colors in the visible spectrum. In other words, white.
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Pyro-technicians say the sign of a very good firework-maker is a really good strong blue. The reason blue is so challenging is because copper compounds can be unstable at high temperature.
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Where are we headed with fireworks colors; are turquoise and fuchsia fireworks in our future? Dr. John Conkling, professor of chemistry and a past executive director of the American Pyrotechnics Association, gives us some idea.
"We can usually make a pretty deep red, a nice green, a reasonable blue. Now, if you start to combine the red and the blue, you get violet, lilac, purple. There's interest in being able to make lime-green, a beautiful orange, and so on. That takes a real careful mixing of color technology. We keep getting better and better. As research continues, we're still making advancements...I see no reason why there should be much limitation on the colors we see. It's just a question of R&D (research and development) effort as well as demand.
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 It's usually driven from the entertainment side. A theme park may want a very specific effect for a show they're doing, and they'll say "Give me lime-green." Once a company starts to develop a lime-green, they start thinking, well, we have this new color, let's find some other customers who would like to have it as well." (source)
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Test your fireworks knowledge with this fun set of quizzes. First review the chart, then see how many types you can accurately label.
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Want to learn more about the anatomy of a firework? Great site for the low-down on the sky-high kabooms.  I know I know, cheesy. But I couldn't help myself...

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