How do we make different colored fireworks - Things That Catch Fire or Go Bang - Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)

Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)

5. Things That Catch Fire or Go Bang

How do we make different colored fireworks?

As discussed in the answer to the previous question, the blue part of a gas flame comes from electrons falling from excited high energy levels to their normal lower levels. The same mechanism can be used to get colors other than blue—just add some atoms or molecules that have different energy levels.

The easiest color to add to a flame is bright yellow, from adding sodium. Ordinary table salt will work just fine. You can soak a paper towel in salt, let it dry, and then burn it. Or you can just sprinkle some salt into a gas flame.

Copper is famous for its blue- and green-colored compounds. If you put some copper compounds into a flame, you get pretty blues and greens. Lithium salts make red flames, and strontium salts make even brighter red flames. Barium salts make blue-green flames, and potassium makes violet flames. When you want to make fireworks with sparks of different colors, you can add these compounds to the burning materials.

Some burning materials make colors by other mechanisms. Magnesium burns with a bright white light, because it is hot enough to get into the white region of the blackbody radiation curve. Similarly, orange colors in fireworks are often made from glowing balls of carbon, hot enough to glow orange.