AMONG THE ALPS.
CAPT. W. DE W. ABNEY, C.B., F.R.S. Etc.
DEVELOPMENT—GENERAL OPERATIONS AND PHENOMENA.
A developer is usually compounded immediately before use by mixing two or more solutions, and in order to ensure uniform action it is essential that the constituents should be thoroughly mixed before the liquid is applied to the plate. If the measuring or mixing vessel is large enough, this can be done by agitating the liquid; if not, the liquid may be poured once or twice from one vessel to another.
The quantity of developer necessary for a plate of a given size depends in some degree upon the size and character of the dish that is used, and is smallest when the bottom of the dish is quite flat and has no ridges or grooves. It is false economy to use too small a quantity, and it may be taken that for a quarter plate 1½ oz., for a half plate 2½ or 3 oz., and for a whole plate 4 oz. of developer should be used.
Ebonite, xylonite, or papier maché dishes are the best for all operations connected with negative making, since they are not so liable as porcelain or earthenware to break a plate if it is allowed to drop into them.
When applying the developer to the plate it is important to cover the whole surface of the plate rapidly and in such a manner as to avoid the formation of air bubbles, and the best way is to begin to pour on the developer at one corner of the developing dish and whilst pouring somewhat quickly move the vessel rapidly but steadily along the edge of the dish to the other corner. If there should be any froth or air bubbles on the surface of the developer, the last portions should not be poured out of the vessel into the dish, and then the risk of air bubbles forming on the surface of the plate will be lessened.