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Another class of effects that can be effectively applied to theatre is pyrotechnics. Explosions, flashes of light, sparkling effects, and puffs of smoke are all possible to achieve using pyrotechnics.

Any pyrotechnic device used in a theatre setting is electrically triggered. Devices called electric matches are used to ignite whatever type of pyrotechnic material is being used. Pyrotechnic material is placed in pots, which are bases with very strong metal walls to hold the pyrotechnic material, and hookups for electric matches. They also have a connection for the pyrotechnic ignition control box, which is a special controller used to set off the effects.

Two main types of pots exist. One type is for flash-style effects, where a large flash of light and a puff of smoke are produced. These pots tend to have a very wide top so that pressure can not build up and cause an explosion. Figure 8.5 shows a typical flash pot. The other type of pot is the concussion pot, which differs from the flash pot in regards to the shape of the pot. It is typically a narrow, thick-walled tube that tends to allow pressure to build up such that a concussive sound will be created when material is ignited in it. Figure 8.6 shows a typical concussion pot.

**Figure 8.5:** A *flash pot*, a device used to contain a pyrotechnic effect. The effect produces a flash of light and a large puff of smoke.
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**Figure 8.6:** A *concussion pot*, another device used to set off pyrotechnic effects. Concussion pots produce a loud explosion and a small amount of smoke, making them most useful for simulating a loud cannon fire or something similar.

Special chemical compounds are used for each pyrotechnic effect. These compounds are purchased from theatre supply houses, generally an an A/B mixture. This means that the materials are shipped such that they are not capable of being ignited until mixed together. Once the materials are mixed, the pyrotechnic compound is considered live, and treated with the same care as gunpowder. These compounds should not be stored live! Mix only as much as is necessary for a given performance. Mix it at the beginning of each performance, and discard any leftover material by following the disposal directions on the packaging. Appropriate chemical fire extinguishers should be present on both wings of a stage, should a small fire start due to pyrotechnics.

Pyrotechnics are among the most dangerous effects used on stage. The potential exists for people to get badly hurt, sets to catch on fire, or any of a number of other unpleasant things. For this reason, they must be used with extreme care. It is imperative that no flammable materials are within the vicinity of a pyrotechnic device when it is set off -- this means actors, curtains, the set, etc. It is common practice to locate the pyrotechnician (person in charge of assembling and igniting the pyrotechnic effects) in one of the wings of the stage so that they have a clear view of the pyrotechnic devices before deciding to fire them. It is important to keep in mind that if the pyrotechnician judges that it would be unsafe to fire a device, the resulting missed cue is lot better than a potential fire!

Many states and cities require that pyrotechnicians be licensed before they can legally use pyrotechnics on stage. Even without this requirement, a safety-minded, conscientious and sane person should be chosen as the pyrotechnician.

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