color of firework

The Chemistry of Colors

There are two main mechanisms of color production in fireworks, incandescence and luminescence.

Red

strontium salts, lithium salts

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 aluminum, magnesium, and titanium, burn very brightly and are useful for increasing the temperature of the firework.

Orange

calcium salts

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.

Pure colors require pure ingredients. Even trace amounts of sodium impurities (yellow-orange) are sufficient to overpower or alter other colors. Careful formulation is required so that too much smoke or residue doesn't mask the color. With fireworks, as with other things, cost often relates to quality. Skill of the manufacturer and date the firework was produced greatly affect the final display (or lack thereof).
- Chemistry of Firework Colors

Gold

incandescence of iron (with carbon), charcoal, or lampblack

Yellow

sodium compounds

History Of Firework Colors

Untill the 19th century, fireworks lacked a major aestheticly essential characteristic: color. Pyrotechnicians began to use a combination of potassium chlorate and various metallic salts to make brilliant colors. The salts of these metals produce the different colors: strontium burns red; copper makes blue; barium glows green; and sodium, yellow. Magnesium, aluminum, and titanium were found to give off white sparkles or a flash.
- History of Fireworks

White

white-hot metal, such as magnesium or aluminum

Green

barium compounds + chlorine producer

For nearly 1000 years, the only colors that could be produced by fireworks was the orange flash/sparks from black powder, and white sparks from metal powders. But in southern Italy in the 1830s, scientific advancements in the field of chemistry enabled pyrotechnicians (the modern term for the old "fire masters") to create reds, greens, blues, and yellows by adding both a metallic salt (strontium=red, barium=green, copper=blue, sodium=yellow) and a chlorinated powder to the firework composition. Potassium chlorate (KClO3), a new oxidizer that burned faster and hotter than potassium nitrate, allowed pyrotechnicians to make the new colors deeper and brighter. The harnessing of electrical energy made it possible to obtain pure magnesium and aluminum by electrolysis, which also made fireworks burn brighter. When fine aluminum powder was mixed proportionally with an oxidizer, the resulting mixture - flash powder - burned much hotter and faster than black powder, allowing for the manufacture of louder firecrackers and salutes in aerial fireworks.
- Pyrouniverse.com

Blue

copper compounds + chlorine producer

Purple

mixture of strontium (red) and copper (blue) compounds

Silver

burning aluminum, titanium, or magnesium powder or flakes