Creating firework colors is a complex endeavor, requiring considerable art and application of physical science. Excluding propellants or special effects, the points of light ejected from fireworks, termed 'stars', generally require an oxygen-producer, fuel, binder (to keep everything where it needs to be), and color producer. There are two main mechanisms of color production in fireworks, incandescence and luminescence.
Incandescence
Incandescence is light produced from
heat.Heat causes a substance to become hot and
glow, initially emitting infrared, then red, orange, yellow, and
white light as it becomes increasingly hotter. When the temperature
of a firework is controlled, the glow of components, such as
charcoal, can be manipulated to be the desired color (temperature)
at the proper time. Metals, such as aluminium,
magnesium, and
titanium, burn very brightlyand are useful for
increasing the temperature of the firework.
Luminescence
Luminescence is light produced using energy sources other than heat. Sometimes luminescence is called 'cold light', because it can occur at room temperature and cooler temperatures. To produce luminescence, energy is absorbed by an electron of an atom or molecule, causing it to become excited, but unstable. When the electron returns to a lower energy state the energy is released in the form of a photon (light). The energy of the photon determines its wavelength or color.
Sometimes the salts needed to produce the desired color are
unstable. Barium chloride (green) is unstable at
room temperatures, so barium must be combined with a more stable
compound (e.g., chlorinated rubber). In this case, the chlorine is
released in the heat of the burning of the pyrotechnic composition,
to then form barium chloride and produce the green color.
Copper
chloride (blue), on the other hand, is unstable at high
temperatures, so the firework cannot get too hot, yet must be
bright enough to be seen.
Firework Colorants
| Color | Compound |
| Red | strontium salts, lithium salts lithium carbonate, Li2CO3 = red strontium carbonate, SrCO3 = bright red |
| Orange | calcium salts calcium chloride, CaCl2 calcium sulfate, CaSO4ยทxH2O, where x = 0,2,3,5 |
| Gold | incandescence of iron (with carbon), charcoal, or lampblack |
| Yellow | sodium compounds sodium nitrate, NaNO3 cryolite, Na3AlF6 |
| Electric White | white-hot metal, such as magnesium or aluminum barium oxide, BaO |
| Green | barium compounds + chlorine producer barium chloride, BaCl+ = bright green |
| Blue | copper compounds + chlorine producer copper acetoarsenite (Paris Green), Cu3As2O3Cu(C2H3O2)2 = blue copper (I) chloride, CuCl = turquoise blue |
| Purple | mixture of strontium (red) and copper (blue) compounds |
| Silver | burning aluminum, titanium, or magnesium powder or flakes |
