Special effects in theatrical productions are one of the things that elevates the medium above many other forms of expression. The idea that chemical and physical effects are performed and presented in front of a live audience adds an element of risk and magic to what could be an otherwise straightforward story. If you are attempting to represent a camera flash, and you want to make an impressive theatrical re-creation, it can be dangerous. With the right planning and preparation, however, many prop artists accomplish similar feats every day.
Place your batteries in the battery compartment of your electric flash pot. Make sure the switch is set to "Off."
Place a small amount of white flash powder in your flash pot (2 to 3 tablespoons). How much flash powder you'll need will depend on how bright you want your flash to be. The flash powder creates a small explosion, however, so be very careful not to use too much.
Conceal your flash pot within your flameproof curtain. If you cannot find a flameproof curtain, you can add flame retardant to a normal curtain. You will want to create a prop that will be very near the prop camera used on stage. Old bellows cameras from the early 20th century were shrouded in a black curtain. If you are attempting to replicate that kind of camera flash, then your work is easier. If you are replicating a camera flash of a newer or handheld camera, you will have to create a stage set-up that will allow you to hide your flash pot in something easily accessible by your actor or by a stagehand.
Activate the switch on your flash pot when you are ready to create the flash.
Conceal a small handheld strobe light within the camera or flash apparatus.
Plug the strobe light into an extension cord.
Plug the extension cord into a power strip. Make sure the power strip is set to "Off," and plug it into the wall.
Set the strobe light to create a very slow flash.
Press the "On" switch on the power strip (or have a stagehand do it) when you are ready to create your flash. Turn the power off immediately after the flash has been triggered.
Be extremely careful when using the flash powder method. Stage the effect so the flash pot will not face any actor directly or so that there is enough clearance that no one will be burnt.