THE CHEMISTRY
OF FIREWORKS
I’m John Conkling,
I'm an adjunct professor of chemistry at
Washington College in Chestertown Maryland.
I wrote a textbook, "The Chemistry of
Pyrotechnics: Basic Principles and Theory."
Everything you see in a fireworks
display is chemistry in action.
How the colors are all produced by very
specific chemical mixtures that produce
beautiful color flames.
The sparks are small pieces of fuel
that continue to burn in air.
Without chemistry, you couldn't
have the burning mixtures.
Without the burning mixtures,
we wouldn’t have the fireworks.
LETS TALK CHEMICALS
Every pyrotechnic composition has at least
one chemical that's oxygen-rich an oxidizer:
Potassium nitrate used to make black powder.
Potassium perchlorate used in
a lot of color compositions.
Strontium nitrate is an oxygen-rich chemical,
but the strontium being in there
also produces a red flame color.
Then you need a fuel that's gonna combined
with the oxidizer to produce heat.
The fuels are things like sulfur, charcoal,
aluminum powder, magnesium powder, you vary
your fuel to get a specific heat output.
Specific burning rate to try and get
the exact behavior you looking for
in your chemical reaction.
Most people when they think a fireworks
think of the sky…EXPLODING!
AERIAL SHELLS
This is an aerial shell, this is what people
go to watch a fireworks display at sea.
It's a cardboard casing.
The bottom has a little pocket of black powder,
granular black powder propellant.
There's a very important time fuse that goes
from the propellant into the center of the casing.
That determines when the shells
going to burst up in the air.
The inside of the sphere itself has
a black powder bursting charge,
and then a number of little green pea
marble sized pellets of chemical mixture,
that will produce different colors different
visual effects when the shell burst open.
So this device is placed in a mortar tube,
a fuse or it's gonna be electrically fired
a wire and extends out into mortar tube.
At exact time you wanna fire it,
the signals is given, the button’s
pushed the propellant ignites and
throws this device up into the air.
At the same time this little delay fuse,
which is running from the propellant up
into the center the shells burning.
And then 3,4,5 seconds later, depending on how
high you wanted to go burns into the center in
the shell, light that gunpowder bursting charge,
and - BOOM! - blows the shell open up
in the sky and you see the beautiful colors,
the sparks, all the effects, the patterns
that have been engineered into the device.
We produce colors by using the fact
that different chemical elements,
heated to high temperature,
get rid of this energy by emitting
very specific wavelengths of light.
You know this is the stock room where
we keep a broad assortment of chemicals.
Copper oxide is a chemical element
that will produce a very, very
nice blue flame color for us.
For a red you’d look for a strontium
compound, here’s strontium chloride.
Sodium of course will produce
the yellow orange, sodium silicate.
Calcium makes a nice yellow orange here’s
a calcium nitrate or the calcium carbonate.
If we want a grain color we need some kind
of a barium compound, this is barium acetate.
You look for chemicals that don't strongly
pick up water, that are not hydroscopic.
SAFTEY FIRST!
Anytime we have students in the lab
or I'm doing demos, everybody has to
have their safety glasses on.
Now the glasses I'm wearing are polycarbonate
lenses, which are shatter resistant, but when
I'm around energetic chemicals I always wear
the extra protection of goggles or side shades.
DEMO TIME!
I mean, to produce color you start
with a burning mixture, you need
an oxidizer and a fuel and then
you add the other ingredients,
the color producing ingredients to it.
This is a mixture of potassium
perchlorate and red gum.
(INSTANT REPLAY )
(DRAMATIZATION)
Now instead of red,
now we want to produce green,
so we've added some barium carbonate.
Blue is the hardest color to
produce pyrotechnically.
You need perfect chemistry.
This is copper oxide this is a red
flame composition, from strontium nitrate.
It's a very bright flame because it
has magnalium, a magnesium aluminum
alloy in the composition that
raises the flame temperature.
Now I’ve taken my base mixture and
added moderately coarse magnesium.
This should produce a nice white sparkle effect.
When I'm not sure exactly what's going
to happen when I test something,
I’ll use a little piece of fuse and
I light the fuse and it gives me the time
to step back just a short distance.
There goes the fuse.
AWESOME!
Fireworks make people happy.
There's something about watching that night sky
explode in color and sparks and noise that I think
really gets deep in the human soul and
seeing the night sky exploding in fire,
still brings chills to a lot of people.
