A Manual Of Photography

226 PRACTICE OF PHOTOGRAPHY. Blanquart Everard, Sagnez, and some others, have recom- mended that in the preparation of the highly sensitive photo- graphic papers no brushes should be employed. They pursue the following plan: the solutions are poured upon a perfectly flat piece of glass, and the paper carefully drawn over it, and, if necessary, pressed closer by another plate of glass. A plan of iodizing paper lias been proposed by Mr. Jordan, which offers many advantages. Iodide of silver is precipitated from the solution of the nitrate by iodide of potassium, and tins precipitate being lightly washed, is redissolved in a stiong solution of the latter salt. This solution is applied to the paper, and the paper allowed to dry ; after this it is placed face don n- wards upon some clean water ; the iodide of potassium is removed by this, and a pure iodide of silver left on the paper. If the paper carefully and properly iodized is washed with a very dilute solution of the aceto-nitrate of silver, that is to say, with a solution composed of 10 grains of nitrate of silver to 1 fluid ounce of distilled water, and 10 drops of a concentrated solution of gallic acid be added to another ounce of distilled water, and the two mixed, it will keep for three weeks or a month. It may be used dry in the camera, and afterwards developed with the gallo-nitrate in the usual manner. It will, however, require an exposure in the camera of from ten to twenty minutes, and is, therefore, only useful for still objects; but for buildings, landscapes, foliage, and the like, nothing can be more beautiful. Le Gray recommends as a highly sensitive paper for portraits the following:— Distilled water. .... 6200 grains. Iodide of potassium . ... . 300 „ Cyanide of potassium ... 30„ Fluoride of potassium ... 1 » Papers are washed with this, and then with his strong solution of aceto-nitrate of silver, which is described in the section devoted to the wax paper process. Section III.—M. Martin’s Calotype Process. M. A. Martin, who is aided by the Imperial Academy of Sciences of Vienna in his endeavours to improve the photo- graphic processes, and render them available to the purposes of