Similar to Powder Coating colors, a firework earns bright colors by applying heat. That’s when the real magic happens! But, just packing colorant chemicals into a explosive would create a unsatisfying firework.
Mixing the Firework’s Color
There are two main ways to create color in fireworks: incandescence and luminescence.
First, incandescence is light produced by heat. Heat causes a substance to become hot and glow, emitting infrared, then red, orange, yellow and white light as it become increasingly hotter. When creating a incandescent firework, the temperature of the explosive is controlled and different components like charcoal, aluminum, magnesium, and titanium are used to burn brighter or darker to create the perfect firework color.
The other mechanism is luminescence, which is light produced using energy sources other than heat. Luminescent fireworks absorb energy from an electron of an atom or molecule, which is supplied by the heat of the burning firework, causing it to be unstable. The colors assigned to these fireworks are produced by adding salts including barium chloride (green) and copper chloride (blue).
Creating the Perfect Display
There’s a sequence of events leading to the beautiful, colorful display we love. Lighting the fuse ignites the lift charge, which propels the firework into the sky. The lift charge can be black powder or one of the modern propellants. This charge burns in a confined space, pushing itself upward as hot gas is forced through a narrow opening.
As the fuse continues to burn on a time delay to reach the interior of the shell. the shell is packed with “stars” that contain packets of metal salts and combustible material. When the fuse reaches the star, the firework is high above the crowd. The star blows apart, forming glowing colors through a combination of incandescent heat and emission luminescence.
Resource: Helmenstine, Anne Marie, Ph.D. "The Chemistry of Firework Colors." ThoughtCo, Feb. 16, 2021, thoughtco.com/chemistry-of-firework-colors-607341.
