Firework Colors
 |
| This fireworks display showcases a variety of colors. Most colors come from the excitation of metal ions. |
Chemistry of Firework Colors
How Firework Colors Work and Chemicals That Make Colors
ANNE MARIE HELMENSTINE, PH.D.
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 aluminum,
magnesium, and titanium, burn very brightly and 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.
The energy is supplied by the
heat of the burning firework.
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.
In some cases, 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.
QUALITY
OF FIREWORK INGREDIENTS
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).
TABLE
OF 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, CaSO4·xH2O, 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
|
SEQUENCE
OF EVENTS
Just
packing colorant chemicals into an explosive charge would produce an
unsatisfying firework!
There's a sequence of events
leading to a beautiful, colorful display.
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.
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.
ANNE MARIE HELMENSTINE, PH.D. is an author and consultant with a broad scientific and medical
background.
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PURICARE
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...
CLICK HERE . . . to view company profile . . .
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 | ||
| Reverse Osmosis with Steel Tank & Cartridge Pre-Filters
|
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| Tachmina Solenoid-Driven Chemical Metering Pump - ensures regulated dosing of chlorine into water system without human intervention |
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