Plates may be dried by a current of warm air, but p48 they are much more likely to frill during development; and a very little heat will melt the coating.
If the plates are dried by an induced current of air, the process may be hastened by placing dishes, filled with chloride of calcium, in the air passage to the drying box or room. The chloride will absorb all the moisture from the air passing over it, and the dry air will take up the moisture from the plates.
When the chloride of calcium becomes too damp for further use, place the dishes containing it in an oven and drive off the moisture by heat, when the dry calcium may be again used. By employing such means the plates may be dried in a few hours.
After the plates have become dry, they should be packed in good light-tight boxes and kept in a dry room until wanted for use.
DEVELOPING ROOM FOR DRY PLATES.
Dry plates, ranging in rapidity from one-tenth to one-twentieth the time necessary for a wet collodion plate, are now commonly used in the studios of this country. Of course, plates of such extreme sensitiveness require great care in handling, and absolute freedom from any umpremeditated exposure to white light is necessary to their successful use.
It is therefore necessary that the dark room should be remodelled to suit the requirements necessary to the successful handling of such extremely rapid plates, and in this connection it is proposed to describe the necessary changes and alterations.
Any ordinary dark room may with little expense be fitted for dry plate work. First see that every chink or crevice which might admit white light is stopped or p49 filled up, then fit the door or doors so that they will shut tight and remain closed.
For convenience of access to the room while work is proceeding, and for greater safety, it is well to erect a small porch or ante-room at each door, the entrance to which should be at right angles with the dark room door. The door to this porch and the dark room door should be fitted with springs to keep them closed. With this arrangement one can have access to the dark room at any time by closing one door before opening the other.
If the dark room is lighted by a window, it should be glazed with dark red orange glass, and if the exposure is toward the sun, it should be shaded with a green or ruby colored shade on a spring roller. If the sun never shines in the window, the shade is not necessary.