A Manual Of Photography

M. MARTIN’S CALOTYPE PROCESS. 227 art, has published the following as the best proportions in which the solutions should be made, and the order of their application. For the negative picture— First. Iodide of potassium...................Ioz. Distilled water .................10 fluid oz. Concentrated solution of cyanide)*, of potassium .....) cops. Second. Nitrate of silver ......................7 drachms. Distilled water .................10 fluid oz. Strong acetic acid .....2 drachms. Third. A concentrated solution of gallic acid. Fourth. Good spirits of wine. Fifth. Hyposulphite of soda . . . . 1 oz. Distilled water ...............10 fluid oz. For the positive pictures — First. Chloride of sodium .... 168 grains. Distilled water ..................10 oz. Second. Nitrate of silver ................1 oz. Distilled water ..................10 oz. Third. Hyposulphite of soda ... 1 oz. Distilled water ..................40 oz. Nitrate of silver 30 grains, dissolved in è oz. of distilled water, to be poured into the solution, in a small stream, while it is constantly stirred with a glass rod. Martin particularly recommends the application of the iodine salt first to the paper, drying this, then applying the argentine solution, and drying rapidly. 1 have urged the necessity of this on several occasions : the advantages are, that the iodide of silver is left on the very surface of the paper ready for the influence of the slightest chemical radiation. The use of organic matter in facilitating the change of the silver salts very early engaged the attention of Sir John Herschel; and from time to time, following his suggestions, others have employed various organic matters, albumen and gelatine being the favourite substances. These have been principally used for the purpose of spreading photographic preparations on glass— which we shall have particularly to describe: at the same time they are stated to have been employed with much advantage on paper by some photographists. For the negative pictures.