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From George Eastman House : Notes On Photographs

The use of pyrotechnics to illuminate subjects for photographic exposure dates to the mid-19th century. The first practical substance to be used was magnesium. Thin ribbons of the metal were laid in a dish or affixed to a vertical tin tray and lit by matches. The metal burned as a brilliant white light and left behind a thin ash and white smoke. By the early 1870s, special lamps were manufactured to dispense magnesium ribbon; the most fascinating variant of this idea included a clockwork motor that fed the ribbon through a hole in the center of a polished reflector. Magnesium ribbon dispensers continued to be popular until after the turn of the century.

By the 1880s a special flashlight or flashlamp for burning magnesium powder had been introduced. When a match was set upon a small pile of magnesium powder, only the outer areas exposed to the air would burn completely. Magnesium powder flashlights were designed so that an alcohol lamp would be lit first, establishing the means of ignition. The magnesium powder was loaded in a chamber with a hinged lid. When the exposure was to be made, a pneumatic bulb was squeezed and magnesium was blown from the chamber past the open flame. In this way fine powder had ample oxygen to effect complete ignition. Obviously this was a dangerous system, and a new illuminant was introduced late in the century to make flash photography easier.^[1]

Flash Powder

Flash powder did not require the blow-through style of alcohol flashlamp; in fact it was actually dangerous to use the older-style lamp with the new illuminant. In its most basic form, flash powder was made from a combination of powdered magnesium and potassium chlorate, although there were many variants formulated by photographers in the same secretive way fireworks are designed. Certain additives to the basic mixture, such as ammonio-chloride of copper, would create a cool-blue color that was more actinic.

Flash powder could be poured on any surface in any amount and lit with a match or spark. The most popular apparatus for flash powder was a metal tray on a handle that was fitted with a spring-loaded rotating friction wheel that rubbed against a flint like those used in a cigarette lighter. Depressing a lever or button released the wheel to produce a shower of sparks that ignited the powder. To make the exposure, the photographer would uncover the lens by removing the cap or would trip the shutter with one hand and then set off the flash with the other hand. The shutter speed B (or bulb) was specifically suited for this type of exposure. As long as the pneumatic bulb was depressed, the shutter remained open; once the bulb was released, the shutter would close. Flash powder continued to be used for interiors, banquets, and night exposures until the invention of vacuum flashbulbs long after the turn of the century.^[2]

1. ↑ Osterman, Mark. 2007. Flash Photography. In The Focal Encyclopedia of Photography: Digital Imaging, Theory and Applications, History, and Science, ed. Michael R. Peres, 80, Focal Press.
2. ↑ Osterman, Mark. 2007. Flash Powder. In The Focal Encyclopedia of Photography: Digital Imaging, Theory and Applications, History, and Science, ed. Michael R. Peres, 80, Focal Press.