How an Aerial Fireworks Shell works:
Once lit, the quick match lead burns into the lift charge at the bottom of the shell. The lift charge is composed of granular black powder that burns hot and flashes quickly. This produces an overpressure of hot gases underneath the shell which rapidly accelerates it out of the mortar tube. The black powder lift charge also serves another purpose of igniting the time fuse on the shell. The time fuse is what controls when the shell will burst in the sky. Typically for a 3" shell, the time fuse will burn for about 2.5 seconds. As shell sizes go up, the longer the time fuse delay. The delays are timed so that the shell breaks at it's apogee (point at which the shell is relatively motionless in the sky and gravity begins to take over) to give the most symmetrical look. Once the time fuse reaches it's end, it lets off a quick flash into the burst charge of the shell. The burst charge usually consists of rice hulls coated with a chemical mix similar to black powder which burns hot, fast, produces a large quantity of gas, to ignite all of the stars in the shell and blow the shell open at a high velocity. The shell casing is usually "spiked" with string to make it more rigid and withstand higher pressures; thus, giving it a bigger boom, and a larger spread of it's stars. There are spherical shells and cylindrical shells which give different effects. A spherical shell will break with almost perfect symmetry, allowing for spherical patterns to be made in the sky. A certain type of shell that will stick out in a display, is the salute shell. A salute shell is filled with only flash powder which causes (the larger ones) to detonate in the sky, as opposed to deflagrate like a star shell. They have no stars and make a thunderous boom in the sky. Don't forget to turn you car alarms off! The red piece on the shell in the photo to the right is a "tail" or "comet" which burns as the shell rises into the air, causing a trail of sparks to follow the shell during it's accent (This effect is made to simulate a rocket taking off).
What is a Fireworks Mine?
A Mine is a device in which a number of stars are shot out of a mortar with a charge of black powder. It will look like an aerial shell exploded in the tube. Picture of five glitter mines on the left.
What is a Fireworks Comet?
A comet is basically a large star, which is shot out of a mortar tube with a charge of black powder. Typically, the comet will have a large "tail" that will follow it up into the sky. A pyrotechnic "tail" would be made with the addition of charcoal to give a gold tail, and titanium or aluminum to give a silver tail. (Many other possibilities). Comets do not always have tails. They can also be a solid color, such as blue, red, green, etc.
What is a Fireworks Waterfall?
A Waterfall (a.k.a. Niagara Falls) is designed to give the look of exactly what the name says, a waterfall. It utilizes what essentially amounts to an array of slow burning Gerbes (a.k.a. fountains) being simultaneously fired upside down from an elevated position. The slow burning composition produces bright sparks which create the visual effect of a waterfall.
Candles (a.k.a. Roman Candles)
A device which is similar to a comet, except there is more than one shot per device. Candles can have a wide range of effects and number of shots. Each candle is constructed with a star that sits on top of a black powder charge, with a delay composition below the black powder charge. This delay composition burns slowly to allow for a time lapse between one shot and the next. As soon as the delay composition burns through, the next star and corresponding "lift" charge are ignited. This process repeats until all the stars are fired. The picture to the right has the candles on the left and a few cakes already foiled on the right.
What is a Set Piece?
These utilize a number of colored lances (small flares) which all together form a pattern or word. They typically burn for one minute. All of the lances are simultaneously lit with quick match.