A Manual Of Photography

92 HISTORY OF PHOTOGRAPHY. availing ourselves of tins easy method of producing a tolerably sensitive daguerreotype paper. These are, certain irregular formations of oxides in different states, and the revival of metallic silver in some parts of the surface. I next spread papers with the pure oxide formed by chemical means, and also the protoxide, and many of its salts. These papers were not very readily affected by iodine, or influenced by light during short exposures. Silver is revived from its solutions by hydrogen gas; conse- quently, nothing is more easy than, by washing a paper with nitrate of silver in solution, to procure a fine silver paper, by passing a current of hydrogen gas over it. A picture of a peculiarly delicate character may be produced on this kind of paper ; but it has not the required sensibility, and there is a great want of contrast in the lights and shadows. It may be interesting to state, that the yellow-brown phosphate of silver is as readily acted on by iodine as the oxides, and is quite as sensitive to luminous influence. Phosphuretted hydrogen gas effects the revival of metallic silver, and the surface produced by means of this gas, used as the hydrogen was in the former case, is of a fine steel-blue, which colour arises from a portion of phosphorus having entered into combination with the silver. These kinds of paper comported themselves in every respect as the metallic tablets—were equally sensitive, and produced pictures as delicately beautiful. Unfortunately, however,owing to the spontaneously inflammable nature of the phosphuretted hydrogen gas, it is not safe to operate with it. After various ineffectual contrivances to overcome this difficulty, I was obliged to abandon the use of this gas entirely—warned of the danger I incurred, by several violent but fortunately harmless explo- sions. The vapour of phosphorus and of sulphur was also tried, and many very beautiful effects were produced. At length, however, I stopped at sulphuretted hydrogen, which answers in every respect.1 To prepare this, soak a paper of very firm texture, not too much glazed, in a weak solution of the muriate of ammonia. It must then be wiped with clean cloths, and carefully dried. The paper is then dipped into a weak solution of the nitrate of silver, and the small bubbles which form on its surface are carefully removed with a camel’s hair pencil. When the paper is nearly, but not quite, dry, it must be exposed in a closed vessel to sul- phuretted hydrogen gas, slowly formed from the sulphuret of 1 A very interesting account of the revival of gold and silver from their solutions by these gases will be found in a tract on Combustion, published by Mrs. Fulhame.