A Manual Of Photography

262 PRACTICE OF PHOTOGRAPHY. one contains, and a little liquid ammonia, not strong, but the ordinary liquor ammonia of the shops. If this is not at hand, a little caustic potash or soda will answer as well, the purport of it being to remove any greasy matter attached to the surface, as glass is frequently marked with soap ; and although it might appear at first sight that clean water must thoroughly remove this article, the operator will be certain of spoiling many of his pictures if he depend upon water alone. The plan Mr. Horne recommends is as follows :—Pour upon the plate a few drops of ammonia, rub it well over both surfaces, and thoroughly rinse through two waters, allowing the water to flow over the plate either by pouring from a vessel or holding under a tap ; now, witli a clean cloth wipe perfectly dry, and finally well rub witli a leather. Simple as this may appear, there is much more in it than will be at first imagined, for unless the glass is free from stains it is quite impossible to be successful. The plate may be washed perfectly clean, but the surface not thoroughly dried. Then, again, some hands are very warm, and if the plate is allowed to rest too much upon any one part, or held too long in the fingers at any one particular spot, that will become warmer than the surrounding part, from the glass being a bad conductor of heat. The cloth and leather should therefore be sufficiently large, that the plate may be as it were insulated as much as possible from the hands, that no unnecessary heat shall be applied. At the same tune the employ- ment of a warm cloth is very useful, for the heat is then equally diffused over the plate, and, what is very essential, the surface perfectly and quickly dried. Coating the Plate.—It has already been pointed out how necessary it is to handle the plate as little as possible in cleaning; we therefore suppose the operator to have the plate in a clean dry leather, from which it is taken to receive the collodio-iodide of silver. The plate must be held by the left hand perfectly hori- zontal, and then with the right a sufficient quantity of collodio- iodide should be poured into the centre, so as to difluse itself equally over the surface. This should be done coolly and steadily, allowing it to flow to each corner in succession, taking care that the edges are all well covered. Then gently tilt the plate, that the superfluous fluid may return to the bottle from the opposite corner to that by which the plate is held. At this moment the plate should be brought into a vertical position, when the diagonal lines caused by the fluid running to the corner will fall one into the other and give a clear flat surface. Io do this neatly and effectually, some little practice is necessary, as in most things, but the operator should by no means hurry the