This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Indoor Work With Magnesium And Flashlight Powders. Photography by flashlight is now within the reach of all without danger, difficulty, or much expense. Ordinary care, of course, is still necessary and it is advisable to know something about the materials with which you have to deal. There are many kinds of apparatus available, all of which are perfectly safe if understood and handled properly.
Flashlight Powder. Magnesium is the principal medium used for flashlight work, either alone in the form of sheets or powder, or mixed with some chemical compound such as Potassium Chlorate, Potassium Bichlorate, Potassium Nitrate, Antimony Sulphide, Permanganate of Potash, Gun-Powder or Pyroxyline. Some of these compounds are extremely dangerous and, therefore, we will not give them any consideration, as there are many excellent flashlight compounds on the market which are perfectly safe to handle.
Magnesium Flash-Sheets. The most simple and least dangerous of all flashlight materials are Eastman's flash-sheets, for with these sheets, all that is required is to pin one or more on to a white cardboard and stand the latter on end, or you can even hold the cardboard in the hand and by touching a match to the lower edge of the sheet it will burn rapidly and give a very bright light. Flash-sheets, however, are not instantaneous and, therefore, should only be used when photographing still-life, interiors, etc. As the volume of light from flash-sheets is not great the sheets can be used only where the amount of illumination required is small.
Pure Magnesium Powder. Pure magnesium gives a very white light, but as it does not explode from fire or fuse, as do Luxo and other similar flash-powders, a machine must be used with a spirit-lamp attached, into the flame of which the powder is blown from a magazine chamber, where it burns with a very brilliant white light. For a magnesium flash-machine see Illustration No. 31.
Illustration No. 31 Magnesium Machine. See Paragraph No. 475.
Pure magnesium powder is seldom used for portraiture, as it is not instantaneous. Its principal use is found in commercial work and the beginner should not attempt to use magnesium light until he has had some experience with flash-powders generally. One objection against the use of pure magnesium powder is that it cannot be handled as conveniently as flash-powder. It is not possible to place a heap of powder on any surface and fire it with a match, as is the case with magnesium sheets or flash-powder. When pure magnesium powder is employed, it is absolutely necessary to use a regular magnesium lamp containing a rubber tube with which you blow the magnesium into the flame, when all the powder will ignite; while, if piled in a heap and an attempt made to ignite it, it will simply make a slight flicker and cake up and nothing more result.
476. A suitable magnesium lamp may be procured from any supply dealer at a slight expense, the smaller sizes selling as low as $1.50. Most of these machines, in addition to the magnesium powder-chamber, have a small pan over an alcohol-fed wick with a blow tube directly over the center of the pan, operated by a pneumatic bulb. With a little practice a uniform flow of powder can be forced over the alcohol flame by substituting for the rubber bulb and tube a 3-ft. rubber tube with a glass mouth-piece. By blowing through this tube, you will be able to secure a uniform flow of the powder instead of a series of short puffs, and thus attain a more even distribution over the flame. Be very careful, however, not to draw the air from the pan into the mouth. This can be easily avoided by taking a good long breath of air before applying the lips to the tube. It is possible to regulate the force of the air, without the mouth-piece, by using a rubber tube to which is attached an ordinary pneumatic bulb and a large storage bulb. The storage bulb is fed from the small bulb until full and uniform pressure is then given to the storage bulb while the powder is blown evenly into the flame of the lamp.
477. If the blow is too violent, the powder will be expelled from the pan unburned; if too feeble the powder will cake in the pan before being ejected. When the powder begins to cake the most violent blow from the mouth or bulb is insufficient to force it out. Therefore, care must be exercised not to blow too violently, but with sufficient force to ignite all the powder that is blown into the flame.