121. The dark - room for the manipulations of the plate should be convenient to the glass studio, so located that it can be thoroughly ventilated at top and floor, and kept of even temperature all the year around. It should be as large as your space will admit,say not left than twelve by fifteen feet It should be provided with a developing sink, another for fixing, and a third, under a tap, for washing the plates thoroughly. dust enough shelving to accommodate the needful articles of use in the dark-room, and no more.
121, The dark - room should be, of course, in the immediate vicinity of the skylight. It should be wholly lined, floor, sides, and ceiling, with wood, and painted in oil of a light yellowish color, which allows of its being wiped off, as occasion may require, with a damp cloth. If the room happens to be papered, and the ceiling white - washed, the paper, if in good order, should be painted as above described; the ceiling must be scraped off and also painted. No projecting ledges must be permitted as deposits for dust. This room should contain absolutely nothing except what appertains immediately thereto, such as bath-holders, a shelf to stand the plate-holders, a small shelf handy to the sinks for the developers and strengthening solutions, and a small shelf to contain the plates and collodion vials. Everything else in the shape of bottles, chemicals, boxes, etc., must be banished. This room need not be larger than eight by ten feet square.
A sash about two feet square, glazed with yellow (orange-yellow) glass should be let in, immediately opposite the tank, at such an elevation that the operator, in developing, need not stoop or bend over too much. This room is never to be swept out, but a mop is pro-vided, with which the room must be mopped out every morning before commencing work. The sash above alluded to must be provided with shutters or covers, that more or less light may be shut out as desired. I need scarcely add that every particle of white light must be carefully excluded. When such a window is impracticable, you may use either gas or a lump, inclosed in a lantern-frame glazed with orange glass. Do not commit the too common error of having this room too dark. It should be sufficiently light for all operations without the least fumbling. The shelf containing the plate - holders should be covered with thick bibulous paper, for absorbing all drippings of silver, and for resting the edge of the plate a moment or so after its immediate extraction from the bath. Above all, do not neglect the great precaution of thorough ventilation. If possible, a trap - door should be let into the ceiling, or else the door should face the window, when a draught of air can at any time be admitted. - Elbert Anderson.
122. A cupboard for chemicals is also a good arrangement. The most rigid cleanliness should always be practised here, and "house - cleaning" of frequent occurrence. All white light should be excluded, and only that which is yellow, ruby, or orange admitted. A great convenience, not only, but a great necessity in the dark-room, is plenty of clear, pure water, and a proper arrangement of the tanks, with a means of saving such waste as is of value, and of getting rid of the rest without injury to the health. Dust in every shape and form should be most enthusiastically opposed in the dark-room. It should not be allowed to enter the door; it should not be brought in, or created by allowing the drip from your solutions to crystallize on the floor. Walk the floor gently; wipe it up vigorously with damp cloths daily.
122, The Tanks. - The arrangement of the tanks for developing and washing maybe something after the following plan:
Immediately in front of the yellow-glazed sash, a b (which should be constructed so as to raise and lower like an ordinary window), are placed two trays, c D, about two feet long by eighteen inches wide, and three inches deep. The water is admitted from a reservoir by a pipe containing two cocks, E F, which are so constructed as to give a smooth crystal bar of water without spattering. The plate is to be developed over the tank D, and well washed, both on the back as well as the front. The silver, which is perfectly precipitated by the iron in the developer, and also the excess of nitrate being washed off, flows from the tray d through the waste-pipe H into the tank g. Observe that the pipe H should be led to the side of the tank G, the water thus flowing against this side is prevented from stirring up the settled silver on the bottom of the tank g. The negative, after being removed from the hypo, tray (which should be in a convenient neighborhood), is drained a few minutes, and then thoroughly washed over the tray c, the water flowing through the pipe J into the general waste-pipe L. Into the tank g is inserted a stop - cock. k, four inches from the bottom of the tank; this cock is connected with the waste-pipe k by means of an india-rubber hose, which may be removed and replaced at pleasure. No further treatment is required. The precipitated silver settles quietly down during the night; the water, being quite clear above, may be drawn off every morning.
Finally, this room should be provided with a gas - stove, upon which is placed a tin of water during the winter, for maintaining a healthy and breathable atmosphere; a thermometer should be hung conveniently, and an even temperature kept up between sixty and seventy degrees Fahrenheit. - Elbert Anderson.
123. As in any other work, so in the dark - room, the photograph should look well after his light supply. If the light is allowed to - wine into. the dark - room from the side, it should be from a window sufficiently low and sufficiently forward to enable one to receive a good light underneath the plate when held for development The drawing below supplies an admirable model, though supplied with rather more than properly belongs to the work of die dark - room.