A Manual Of Photography

MB. CUNDELL’s PBOCES8. 219 minutest black specks, the object is to spread over its surface a perfectly uniform coating of the iodide of silver, by the mutual decomposition of two salts, nitrate of silver and iodide of potassium. There is a considerable latitude in the degree of dilution in which these salts may be used, and also in the manner and order of their application ; but as the thickness and regularity of the coating depend upon the solution of nitrate ot silver, and upon the manner in which it is applied, 1 think i ought by all means to be applied first, before the surface of the paper is disturbed. I use a solution of the strength of seventeen grains to the ounce of distilled water. 3. The paper may be pinned by its two upper corners to a clean dry board a little larger than itself ; and, holding this nearly upright in the left hand, and commencing at the top, apnlv a wash of the nitrate of silver thoroughly, evenly, and smoothly, with a large soft brush, taking care that every part of the surface be thoroughly wetted, and that nothing remain un- absorbed in the nature of free or running solution Let the paper now hang loose from the board into the air to dry, and by using several boards time will be saved. . 4 The nitrate of silver spread upon the paper is now to be saturated with iodine, by bringing it in contact with a solution of the iodide of potassium: the iodine goes to the silver, and the nitric acid to the potash. „, 5. Take a solution of the iodide of potassium of the strength of 400 grains to a pint of water, to which it is an improvement analogous to that of M. Claudet in the daguerreotype, to add Ao grains of common salt. He found that the chlorinated iodide of silver is infinitely more sensitive than the simple iodide, and by this addition of common salt, a similar, though a remarkable, modification is obtained of the sensitive oompounc Pour the solution into a shallow flat-bottomed dish, su e y larm to admit the paper, and let the bottom of the vessel be covered to the depth of an eightli of an inch. The prepared side of the paper, having been previously marked, is to be throng 1 in contact with the surface ot the solution, and, as it is dcsir.i c o keep the other side clean and dry, it will be found convenient, before putting it in the iodine, to fold upwards a narrow margin along the two opposite edges. Holding by the upturned margin, the paper is to be gently drawn along the surface of the liquid until is lower face be thoroughly wetted on every part; it will become plastic and in that state may be suffered to repose for a few moments if contact with the liquid: it ought not, however, to be exposed in the iodine dish for more than a minute altogether, as the new compound, just formed upon the paper,