Fireworks
Many a holiday would be incomplete without a proper fireworks display. But how fireworks, well … work?
Getting bang for your buck
The heart of fireworks is simple, gunpowder. How gunpowder itself works is actually rather simple.
Start with a charcoal grill, like many fired up on a weekend or special day.
Clearly, the burning charcoal gives off heat energy, no? To do so, it takes in oxygen from the air and together they burn to make the usual results, including some great food!
Now jazz it all up by mixing some powdered charcoal with saltpeter (Potassium Nitrate). The saltpeter chemically provides the charcoal with a quick burst of the oxygen it needs, quickly causing it to burn up in an instant.
As a fun illustration, consider the humorous outcome of a group of engineers seeing how quickly they can heat up a charcoal grill (Text link here, Video link here).
So, so far we have a quick way to burn charcoal. Fine. But no bang as of yet. For that, we add some sulfur.
Why? Sulfur is easy to heat to gas. And sulfur gas will want to expand out.
Are we there yet?
Almost.
We now have gunpowder. But by itself, there is no explosion. In fact, a trail of gunpowder was often used as an early fuse. Someone lights one end and it burned along the trail to the actual explosive. You can see a video here. (sadly for us, modern gunpowder is smokeless and so the effect is less dramatic in the video)
To give bang, simply enclose in some container, even a simple piece of paper will do. Now the gas is held up for a short time and can only come out all at once.
Now we have an explosion!
Getting up in the world
Now, let's talk about the fireworks themselves.
The first item of business is to get it up in the air for all to see. There are two ways to do this:
One could use some gunpowder to make a rocket and shoot it up. Here some of the gunpowder at the bottom of the firework is packed not as tightly, so it burns slower. Also, a hole in the bottom allows gas to escape, shooting it into the air.
The aerial or mortar style uses a small amount of gunpowder to shoot the firework up and through a cardboard tube and into the air like a cannon. Most commercial firework displays use this approach.
Shock and awe
So we have the power, as well as the height above the ground. Now for the part we all love.
The business end of fireworks has at its center a gunpowder charge that, when the time is right, explodes and scatters the fun around. The firework contains pellets called “stars” that create the sparkles.
The stars produce different colors depending on what they're made of. This is because elements give off different colors of light as they burn. Below are some examples of elements that get used:
Red – strontium, lithium
Orange – calcium
Yellow – sodium
Blue – copper
Electric white – magnesium or aluminum
So stars containing copper, for example, will burn with a blue glow.
So next time you are watching a fireworks display try (if you can squeeze it in between the oohs and awes) to think of what goes into making them. And remember the words of the physicist Richard Feynman:
Poets say science takes away from the beauty of the stars - mere globs of gas atoms. I, too, can see the stars on a desert night, and feel them. But do I see less or more?
On the web
This is an animated explanation of how fireworks and roman candles work.
This is a recorded news segment where a reporter someone in charge of setting up a fireworks display. He shows what the inside of a firework looks like and how the display is set up.
This is a segment from the Discovery channel showing a firework being made.
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