A Manual Of Photography

TUE CATALYSOTYPE. 79 Section III.—The Catalysotype. This process of Dr. Woods’ is capable of producing pictures of superior excellence. Owing to the inconstancy of the iodine compounds, it is a little uncertain, but, care being taken to in- sure the same degree of strength in the solutions, a very uniform good result may be obtained. The process and its modifications are thus described by the inventor. “While investigating the property which sugar possesses, in some instances, of preventing precipitation, I noticed that when syrup of ioduret of iron was mixed in certain proportions with solution of nitrate of silver, the precipitate was very quickly blackened when exposed to the light, and I thought that, if pro- perly used, it might be employed with advantage as a photo- graphic agent. If not entirely without profit, it would hardly repay the trouble of reading the history of all the experiments I tried in order to prove whether or not this idea were correct; for there were many difficulties to be overcome, and unexpected hinderances to be surmounted, before I could be certain of success. However, the results at which I have arrived make me hope that my trouble has not been thrown away, and that a photographic process has been discovered, which is more manageable and more satisfactory than any which has before been used; and I think that the pictures produced by it are more minutely and delicately brought out, and the time for their production at least not longer than is required by any other method. “ To enter very minutely into the particulars, or to explain the rationale of the process, would be too tedious ; however, it is so simple, that those who will feel any pleasure in trying it will, I am sure, easily succeed, and to attempt any explanation of its theory would, in the present state of our knowledge of light, be advancing a mere hypothesis: I will, therefore, only state generally the method in which the paper is prepared, and then, briefly giving my reasons for such parts of the process as are not at first sight obvious, will thereby enable the experimenter to be guarded against the failures that these precautions are intended to overcome. “ Let well-glazed paper (I prefer that called wove post) be steeped in water to which hydrochloric acid has been added in the proportion of two drops to three ounces. When well wet, let it be washed over with a mixture of syrup of ioduret of iron half a drachm, water two drachms and a half, tincture of iodine one drop.