Fireworks were accidentally invented by the Chinese in 200 BC But it wasn’t until a thousand years later that Chinese alchemists developed fireworks in 800 AD. These first fireworks were mostly bright, noisy mixtures designed to scare away evil spirits – not the colorful and controlled explosions we see today. Fast forward another millennium and the Italians discovered how to add color introducing various elements into the flammable mixture. Adding the element strontium to a colored pyrotechnic mixture produces a red flame; copper, blue; barium, green; and sodium for yellow.
Too many or too few chemicals cause significant changes in the temperature and therefore the wavelength of the color seen. The proper mixture of chemicals, when lit, produces enough energy to excite electrons and emit different colors of light.
Although the chemistry of these colors is not new, each generation seems to be excited by the colors spread across the sky. We now have a wide range of flame colors: red, green, blue, yellow, purple and variations thereof.
Each color works the same way. As different elements ignite, they release different wavelengths of light that translate into different colors.
Making that perfect blue fireworks
Not all fireworks colors are equally easy to create. I believe that several of my colleagues in pyrotechnic research and development would agree with me that blue is the most difficult color to produce.
This is because the night sky has a shade of blue, meaning most blues don’t show up either. If you try to make the blue lighter to contrast with the background, it may look washed out. The right balance of copper and other chemicals in the flame or combustion reaction produces the best blue flame color in a firework.
I took this into consideration when trying to create the best blue flame color, which I call pillbox blue. It’s bright enough to stand out in the night sky, but it’s still a rich blue. I have more than 20 blue pyrotechnic formulas and I found one that comes very close to that elusive hue.
Another difficulty in creating an intense blue color is that the chemistry is not simple. It requires a combination of several chemicals and the element copper. When copper ignites, the electrons surrounding the copper atoms become excited and energized in the flame. When electrons release this energy, it appears to observers as blue light. Each color works the same way. As different elements ignite, they release different wavelengths of light that translate into different colors. So when you see blue-colored points of light creating a pattern in the night sky, you are actually seeing excited electrons releasing energy as blue light.
This article was republished from The conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you understand our complex world. It was written by: Paul E. Smith, Purdue University
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Paul E. Smith is president of the Pyrotechnics Guild International, Inc. He is a member of the American Pyrotechnics Association, the National Fireworks Association, and the International Pyrotechnics Society.
