In Russia, they have fireworks too -- they put you up against the wall and yell "FIRE!" It works.
-- Yakov Smirnoff
Definition from WordNet:
firework, pyrotechnics -- ((usually plural) an explosive device that burns with colored flames)
Fireworks are pyrotechnic devices. That is, the general idea is this: You light a fuse, wait a few seconds, and something goes flash and/or bang.
Note that "fireworks" can refer to either the individual combustible units or to a display of such units being ignited.
First, I'll recommend that you check out the excellent node
explosion in case you don't fully understand what an explosion actually is. While it's not necessary to understanding this writeup, it will be helpful in understanding
what happens after you light that fuse.
Physical structure:
The most basic of fireworks is the firecracker. A firecracker is composed of a container, usually made out of paper, filled with an explosive material (black powder, aka gunpowder, is most commonly used). A fuse is then added, in order for there to be a time delay between the point at which the firecracker is lit and the point at which the charge detonates. Firecracker are often packaged together with their fuses intertwined, so that lighting one will ignite the others in a sequence that sounds like gunshots. *POW POW POW POW POW POW POW!*
While a firecracker is designed to go off instantly in a loud bang, another of the vast repertoire of a nationalistic holiday celebrator's arsenal is the sparkler. A sparkler is a tube of paper rolled around a wooden stick. Once it has been lit, the sparkler, well, sparkles, and can sometimes emit noise Assuming it is lit at the end, a sparkler will burn for a minute or more. It achieves this through a slightly different mix of compounds than that contained in a firecracker. A firecracker contains black powder as fuel, an oxidizer, metal powder (for sparkle fun) and a binder, such as starch. When burned, this mixture will burn slowly from one end to the other, as will a cigarette. The key to the speed of the reaction is that the chemicals are present in different ratios than that of a firecracker. See ( http://static.howstuffworks.com/gif/fireworks-sparkler.jpg ) for an example of a sparkler burning.
Next we come to those most delicious of (occasionally) illegal beauties, aerial fireworks. A small mortar shell, of the kind that you might buy next July, is going to be about the the size of a plum. In comparison, the fireworks you see in a public show are often as large as a melon. Nonetheless, they both share a similar physical structure.
A standard mortar firework is a ball of "firework" with a cylinder of booster fuel strapped to the bottom. It has a long fuse, an explosive booster charge for getting the mortar into the air, and a round shell filled with gunpowder and "stars", made of similar material to a sparkler. A bursting charge is responsible for igniting the gunpowder.
Note, however, that while small shells are usually self-propelled, larger shells are fired more like cannonballs: they are placed in a metal tube on top of gunpowder, which is ignited to eject the shell from the tube. The ejection will also light the fuse of the shell.
Many layers of complexity can be built upon this foundation: different materials can be mixed with the gunpowder to create sounds. Different "stars" can be embedded in the gunpowder mixture to create snakes, willows, and your standard star points, all in different colors. The stars can be arranged in different patterns within the shell to create different designs in the sky.
The next level of complexity are multi-stage shells that will, say, make a willow pattern and then, when the willow is formed, have the ends explode in a flash and a bang. Sometimes this is accomplished by nesting shells within shells, and sometime it is possible to get a multi-stage effect using only one shell.
The Display
A private display will rarely make use of aerial fireworks, instead relying on firecrackers, sparklers, and "fountains" (Roman Candle), as well as gimmicky pieces like small cardboard cars that are propelled by a stream of fireworks coming from the rear. Also popular are fireworks that spin and whistle when ignited, and small black pellets that expand into a carbon "snake" when lit. Of course, in some states aerial fireworks are illegal, while in others they are not; I do not, of course, imply that this causes a discrepancy in the rate of private aerial displays.
A public display, on the other hand, will usually be all-aerial. For the largest shows, massive banks of computer-controlled mortars are set up; the preparations can take days of work. A public show has multiple stages, culminating in the finale. The finale can last from less than a minute to almost a half-hour. During this time, aerial fireworks will be set off in quick succession, with the number of fireworks shot off per minute often going into the hundreds. This barrage of light and noise can overwhelm, stun, and amaze you, not to mention that it can also set off car alarms quite easily.
Safety
Top e2 safety tips (I'd say the last is really only 38.9056099% *safety* tip.)
- Always read and follow label directions.
- Buy from reliable sellers.
- Always have water handy (a garden hose and a bucket).
- Never re-light a "dud" firework (wait 15 to 20 minutes and then soak it in a bucket of water).
- Dispose of fireworks properly by soaking them in water and then disposing of them in your trashcan.
- Use common sense; no sticking lit fireworks in bodily orifices, please, unless they belong to somebody else.
- Make sure you are not on fire. This is utmost in importance.
- Oh, right. Enjoy yourself. This is utmost in importance.
Sources:
How Stuff Works ( http://www.howstuffworks.com/fireworks1.htm )
http://www.fireworksafety.com/safety/index.html
If you hunger for more information about advanced pyrotechnics, I would highly advise checking out the illustrious SharQ's (meta) node on the topic.