Text on screen: 'Reactions, Everyday Chemistry. Produced by the American Chemical Society.'
A chemical explodes in a laboratory test chamber.
# TCHAIKOVSKY: 1812 Overture
Fireworks burst into a myriad of colours in the night sky. Words flash up on screen — 'magnesium powder', 'potassium perchlorate', 'strontium nitrate', 'potassium nitrate', 'aluminum powder'. Title on screen — 'The Chemistry of Fireworks.' Fireworks expert John Conkling addresses the camera in a laboratory.
JOHN CONKLING:
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 at a fireworks display is chemistry in action. The colours are all produced by very specific chemical mixtures that produce beautiful-coloured 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, you wouldn't have fireworks.
Text on screen — 'Let's Talk Chemicals.'
JOHN CONKLING:
Every pyrotechnic composition has at least one chemical that's oxygen-rich, an oxidiser.
A list of the oxidisers are supered next to John as he speaks, and inset shots show the chemicals in their powdered form.
JOHN CONKLING:
Potassium nitrate, used to make black powder. Potassium perchlorate, used in a lot of coloured compositions. Strontium nitrate is an oxygen-rich chemical, but the strontium being in there also produces a red flame colour. Then you need a fuel that's gonna combine with the oxidiser to produce heat.
A list of the fuels are supered next to John as he speaks, and inset shots display pictures of them.
JOHN CONKLING:
The fuels are things like sulfur, charcoal, aluminum powder, magnesium powder. You vary your fuel to get a specific heat output, a specific burning rate, to try and get the exact behaviour you're looking for in your chemical reaction. Most people when they think of fireworks, think of the sky exploding.
Fireworks burst in the sky. Text on screen — 'Aerial Shells.'
# TCHAIKOVSKY: 1812 Overture
John holds up an aerial shell — a sphere with a short cone on the bottom, tapering back from the circumference.
JOHN CONKLING:
This is an aerial shell. This is what people go to watch a fireworks display and see. 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 centre of the casing. That determines when this shell's gonna 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 to marble-sized pellets of chemical mixture that will produce different colours, different visual effects when the shell burst open. So, this device is placed in a mortar tube. A fuse, or if it's gonna be electrically fired, a wire, then extends out of the mortar tube. At the exact time you wanna fire it, the signal's 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 centre of the shell, is burning. And then three, four, five seconds later, depending on how high you want it to go, it burns into the centre of this shell, lights that gunpowder bursting charge and — boom! — blows the shell open up in the sky and you see the beautiful colours, the sparks, all the effects, the patterns that have been engineered into the device. We produce colours by using the fact that different chemical elements, heated to high temperature, get rid of this energy by emitting very specific wavelengths of light.
John walks up to a locked door with a 'Danger — Chemical Storage' sign on it and opens it. Text on screen — 'The Stock Room.'
JOHN CONKLING:
Yeah, this is the stock room where we keep a broad assortment of chemicals.
John grabs bottles from two rows of shelves in the stock room.
JOHN CONKLING:
Copper oxide, a chemical that will produce a very, very nice blue flame colour for us, and for 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 green colour we need some kind of a barium compound. This is a barium acetate. You look for chemicals that don't strongly pick up water, that are not hygroscopic.
Text on screen — 'Safety First.' John, wearing protective glasses, walks up to a testing chamber — a cupboard-sized section of the room with a glass window.
JOHN CONKLING:
Safety first. Any time 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 shields.
Text on screen — 'Demo Time.' John stands in front of the testing chamber, holding a jar.
JOHN CONKLING:
I mean, to produce colour, you start with a burning mixture. You need an oxidiser and a fuel. And then you add the other ingredients, the colour-producing ingredients to it. This is a mixture of potassium perchlorate and red gum.
John applies a flame torch to a pile of chemicals in the chamber and they flare up red. Text on screen — 'Instant Replay'. The shot repeats and the image flares to white. A super reads 'Dramatization' as fireworks boom and people cheer.
# TCHAIKOVSKY: 1812 Overture
JOHN CONKLING:
Now, instead of red, now we wanna produce green, so we've added some barium carbonate.
John lights the chemicals in the chamber and they flare up green.
JOHN CONKLING:
Blue is the hardest colour to produce pyrotechnically. You need perfect chemistry. This is copper oxide.
John lights the chemicals in the chamber and they flare up blue.
JOHN CONKLING:
This is a red flame-composition… from strontium nitrate.
John lights the chemicals in the chamber and they burn a bright red for a longer period.
JOHN CONKLING:
This is a very bright flame because it has magnalium, a magnesium and aluminum alloy, in the composition to raise the flame temperature.
John mixes chemicals at a bench.
JOHN CONKLING:
I've taken my base mixture and added moderately course magnesium. This should produce a nice white spark effect. When I'm not sure exactly what's gonna happen when I test something, I'll use a little piece of fuse. And I'd light the fuse — it gives me time to step back just a short distance.
John lights a fuse leading to chemicals in the test chamber.
JOHN CONKLING:
There goes the fuse.
The chemicals explode with an intense yellow flare, and sparks shower down. Text on screen — 'Awesome!' Photos of people staring up in awe at a fireworks display.
JOHN CONKLING:
Fireworks make people happy. There's something about watching the night sky explode in colour and sparks and noise that I think gets really deep in the human soul, and seeing the night sky explode in fire still brings chills to a lot of people.
# TCHAIKOVSKY: 1812 Overture
End titles roll.