[Illustration: ANTHONY'S COMBINED FUNNEL AND FILTER.]
There should be glass-stoppered bottles for containing the developing solutions, especially the pyro; also racks to hold the plates while drying; one finely adjusted scale with apothecary weights weighing to a 1/4 lb.; one camel's hair-brush, 3 inches wide, for dusting the plates before [p054] putting them in the holders for exposure, and also for removing sediment from the surface of the film after fixing and washing.
Thus fitted and furnished, the dark room is ready and well adapted for the most difficult dry plate work, and we will now proceed to the consideration of the
Every manufacturer of dry plates encloses in each box of plates packed for the market a formula for the development of the same.
The various manufacturers of dry plates, whose names will be found in the advertising pages in this book, each have a formula which in some respects differs from all the others, and it is but fair to the maker of the plate, that his formula should be used, unless the operator is of much experience and understands the requirements of each particular kind of plate.
Therefore, while formulæ are given in this connection, although they are known to be of the best, yet in the hands of inexperience they may result to no better advantage than the formula appropriate to the plate used; consequently, we do not urge their use above any other, but rather that to which the operator is most accustomed.
The alkaline pyro developer is now in general use among professional photographers in this country, and there remains no doubt that it is the best developing agent for dry plates that has yet been brought into use.
This developer is composed of pyrogallic acid and [p055] an alkali, either ammonia, sal soda, or carbonate of potash, which, in solution and of proper strength, forms the medium through which the pyro is applied.
To these is added bromide of potassium or ammonium, which is the restrainer, and occupies about the same position or performs the same function as acetic acid in the wet plate developer, and besides being a restrainer it greatly aids in securing intensity and printing quality; and when plates are overtimed in exposure its prompt use may result in securing a good negative.