I. A label and place for everything, and everything in its place with its label.
II. Keep everything clean and free from dust.
These two directions for arranging and caring for a dark room will save hours of labor, and many spoiled plates.
The lighting of the dark room is the first thing which should engage our attention. If the developing is done at night, the stopping out of actinic rays will be avoided; but if in the daytime, care must be taken to shut out all direct rays of light. If the plate is kept in the direct rays of the red light, diffused light will not harm the plate. By diffused light is meant the stray gleams which come through a crack, or a door that does not shut tight enough so but what light shows around the edge.
There are many makes of lantern of all grades and prices in the market, and care should be taken in buying one that it is perfectly light-tight. An actinic ray from the lantern striking the plate will fog it. Most of the lanterns are made for using kerosene. A lantern in which the lamp screws into the bottom is not as light-safe as one which sets wholly inside the lantern, though there is less odor and grease from the kerosene. The trouble with a kerosene lamp is that the confined air soon becomes heated, causing the oil to lose its density, and it oozes out, not only making an unpleasant smell, but greasing the lantern. It will be found much more agreeable to remove the lantern and substitute in its place a candlestick and candle. The one known as the camping or soldier's candlestick is just the thing for a dark lantern. It is a little over two inches high, and made of brass, and costs only fifteen cents.
Adamantine candles are the best, as they last twice as long, and do not melt and run down the sides like the parraffine or tallow candles.
One needs two trays for developing—one 4 x 5 and another 5 x 8. The smaller tray can be used when one has only two or three plates to develop, and both trays where one has quite a number. The two trays are necessary also in transferring the plate from one solution to another, if the developing does not work satisfactorily. The tray for the hypo-sulphite of soda or fixing solution should be 5 x 8, so that two 4 x 5 plates can be fixed at one time.
The developing-trays should be of hard rubber or celluloid, and the hypo-tray of amber glass, so that there shall be no mistaking the developing for the hypo tray.
A four-ounce glass graduate is needed for measuring liquids, and if one has no scales, the dry chemicals should be weighed in the right proportions for use when they are purchased. The hypo can be put up in half-pound packages, and this quantity of fixing solution prepared at one time.
A glass funnel is needed for pouring solutions from trays into bottles, and also for holding the filtering-paper when filtering solutions. The funnel should be fluted, for the ribs make passages for the liquid to pass through the sides of the paper, letting the sediment settle at the bottom of the paper.