An astonishing number of different cultures use fireworks in their celebrations of revolution, love and the passing of time. They may be used for many different types of celebrations within each culture, but the energy of color and sound carry a universal experience.
While, as you may all know, 12th century China first created fireworks to scare off evil spirits, but what you might not know is it was actually the Italians who first created the colors in fireworks.
The colors in fireworks are created by changing the 'color producing chemical' in the pyrotechnic star, which are pellets containing metal powders, salts or other compounds that, when ignited, burn a certain color. These pellets are then added to a 'lifting charge' made of gunpowder and provide the fuel to propel the shells into the air.
There are two main mechanisms of color production in fireworks, incandescence and luminescence.
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.
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
incandescence of iron (with carbon), charcoal, or lampblack
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-hot metal, such as magnesium or aluminum
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.
copper compounds + chlorine producer
mixture of strontium (red) and copper (blue) compounds
burning aluminum, titanium, or magnesium powder or flakes
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