Page:Madras journal of literature and science vol 1 new series 1856-57.djvu/84

72 exciting dish must never be used for developing, and the dishes for developing solutions should not be used for any other purpose, except washing the paper after it is excited, in which case if clean they are not likely to do any harm. After being used with Gallo-nitrate they should be washed as soon as possible in abundance of clean water, and if the Gallo-nitrate solution decomposes rapidly when placed in them, they must be washed with a weak solution of Cyanide of Potassium (5 grs. to one ounce of water), and with plenty of clean water afterwards. The trays for Hypo-sulphite cannot be used for any other purpose except for washing the finished negative. The Photographer will also find it advantageous to have separate measure and funnels for his Aceto-nitrate and Gallic-acid solution.

The paper used in this process is Canson's thin Negative. It is not without imperfections, such as unevenness of texture and minute holes which allow the exciting, and developing solutions to pass through and stain the back of the negative. To the beginner these things are not of much importance, as he must expect to spoil a few papers, but when a little more advanced, he should examine his papers carefully by a strong light, rejecting any that have the imperfections above noted which need not however be thrown away, as the best will do for waxing which fills up any very small holes, and the remainder will do for Positives. The papers should be cut of the same width and half an inch or so longer than the Camera slide; one side of the paper is smoother than the other which is best ascertained by holding it so that the light falls upon it obliquely; this should be marked in two opposite corners with a capital letter, which better defines the side on which the mark is made than a circle or cross.

The solvent may be either whey or distilled water, I believe the former produces the most dense skies and a greater opacity generally in the dark parts of the picture, it is however somewhat troublesome to prepare:—the following method of obtaining it, is perhaps as good as any.