A Manual Of Photography

^.' ^ >" 220 PRACTICE OF PHOTOGRAPHY. upon further exposure, would gradually be redissolved. The paper is therefore to be removed, and, after dripping, it may he placed upon any clean surface with the wet side uppermost until about half dry, by which time the iodine solution will have thoroughly penetrated the paper, and have found out and saturated every particle of the silver, which it is quite indis- pensable it should do, as the smallest portion of undecomposed nitrate of silver would become a black stain in a subsequent part of the process. 6. The paper is now covered with a coating of the iodide of silver ; but it is also covered, and indeed saturated, with saltpetre and the iodide of potassium, both of which it is indispensable should be completely removed. To effect the removal of these salts, it is by no means sufficient to “ dip the paper in water ;" neither is it a good plan to wash the paper with any considerable motion, as the iodide of silver, having but little adhesion to it, is apt to be washed off. But the margin of the paper being still upturned, and the unprepared side of it kept dry, it will be found that by setting it afloat on a dish of clean water, and allowing it to remain for five or ten minutes, drawing it gently now and then along the surface to assist in removing the soluble salts, these will separate by their own gravity, and (the iodide of silver being insoluble in water) nothing will remain upon the paper but a beautifully perfect coating of the kind required. 7. The paper is now to be dried; but, while wet, do not on any account touch or disturb the prepared surface with blotting- paper, or with anything else. Let it merely be suspended in the air ; and, in the absence of a better expedient, it may be pinned across a string by one of its corners. When dry, it may be smoothed by pressure. It is now “iodized” and ready for use, and in this state it will keep for any length of time if protected from the light. The second process is that of exciting or 8. Preparing the Paper for the Camera.—Tor this purpose are required the two solutions described by Mr. Talbot ; namely, a saturated solution of crystallized gallic acid in cold distilled water, and a solution of the nitrate of silver of the strength of 50 grains to the ounce of distilled water, to which is added one- sixth part of its volume of glacial acetic acid. For many purposes these solutions are unnecessarily strong, and, unless skilfully handled, they are apt to stain or embrown the paper: where extreme sensitiveness, therefore, is not required, they may with advantage be diluted to half the strength, in which state they are more manageable and nearly as effective. The gallic acid solution will not keep for more than a few days, and only a small quantity, therefore, should be prepared at a time. When