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THE PHOTOGRAPHIC NEWS. Vol. XI. No. 468,—August 23,1867. CONTENTS. PAGE A New Method of Protecting and Improving Silver Prints 401 The Temperature at which Gun-Cotton Explodes 401 Who Discovered the Collodio-Chloride Process?” 402 Xylo-Paper: A New Material Applicable to Photographic Pur poses. By John Spiller, F.C.S 403 Inventors and Reclaimants. By W. T. Bovey 404 On the Employment of Acetate of Morphine in the Dry Plate Process and as a Developer 405 On the Theory of the Formation of the Photographic Image in the Wet and Dry Processes. By M. N. de Sytenko 40G PAGE Chloro-Lodized Collodion 406 Intensifiers. By Prof. Towler 406 On the Action of Chlorine on Carbonate of Silver.—Preparation of Chlorate of Silver. By Prof. J. S. Stas 408 A « Ray Shield,” &c 410 Correspondence— Carbon versus Silver Printing—" A New Developer’ 411 Talk in the Studio 412 To Correspondents 412 ANEW MODE OF PROTECTING AND IMPROVING SILVER PRINTS. We have pleasure in calling the attention of our readers to a communication from Mr. Spiller, which appears on another page, in which he proposes a mode of protecting and im proving silver prints which appears as sound in principle as it is elegant in application. The practical effect of the operation proposed will be to insulate or envelop every fibre of the print, and the paper containing it, with a water, proof varnish, which shall enrich the tone and brilliancy of the print, and improve the effect of definition, without giving it an offensive glaze. The idea has been suggested by the practice of the War Department in certain preparations of gun-cotton for artillery purposes, in which a portion of explosive cotton and linen fibre are worked together into pulp, and a stout paper for cartridge manufacture, the amount of plain linne fibre added regulating the rapidity of explosion in the finished result. In some other samples of this explosive paper a small portion of ordinary soluble cotton is added, in place of the higher compound or tri-nitro-cellulose. We have examples of the various kinds of paper before us, and the last-mentioned kind illustrates the nature of Mr. Spiller’s proposal. The paper containing the small portion of soluble cotton or pyroxyline has had one end dipped in a mixture of ether and alcohol, which has made a marked change in its character and appearance ; the pyroxyline, being at once converted into collodion, envelops every fibre of the paper, which, on being dried, is found to have become harder and firmer in texture, with a close, fine surface, not glazed, presenting something of the surface, in fact, which a coating of collodion applied to the surface might have given, with perhaps a little smoother, harder surface, and a little less glaze than the applied coating would produce. Mr. Spiller proposes, then, that the makers of photographic paper should add to the pulp, in the process of manufacture, a small portion of pyroxyline, and produce what he proposes to call xylo-paper. This paper may then be employed, with or without albuminizing, to print photographs in the ordin ary way. When the print is finished, it should be sub mitted to a bath of ether and alcohol, or, as Mr. Spiller proposes as efficient, to the vapours in a confined vessel. The trace of pyroxyline, being dissolved, will at once envelop every fibre of the print, and insulate it; the dull appearance of a plain print will vanish, and the image in all its detail will “ bear out ” as though it had been varnished. The. prospect thus held out is, it must be confessed, an attractive one. The operations of the photographer are in nowise complicated ; but he is working with a paper which contains, thoroughly incorporated with it, the elements of an excellent varnish, which merely requires the final applica tion of a solvent to envelop every particle of the image, and of the substance upon which it is formed, with a coating which shall be comparatively impervious to moisture and agencies which may destroy the image, which is at the same time made more brilliant by the transparent film of collodion varnish which is brought into contact with it. One element only of risk to the print occurs to us as possible in such treatment, and this would only arise in the case of the admixture of too much pyroxyline with the paper pulp. If this were done, the basis on which the image rests, being partially dissolved, would of course cause a slight blurring of the image, and would produce, in greater or less degree, the old and well-known appearance of printing through a medium, recently patented in America by Mr. Carl Meinerth, for producing “ mezzotint ” effects, This, in some cases, might improve pictorial beauty; but might, in others, be dangerously injurious to definition. But if the proper pro portion only of soluble cotton were added, no risk to definition could result. Judging by analogy, we might fairly antici pate the production of that singular beauty which belongs to the enamel photographs of M. Lafon de Camarsac, in which, in the process of firing, a slight fusion of the surface necessarily takes place. At present the whole of the experiments upon which the suggestion is based are necessarily purely tentative, and require verifying by absolute practice in producing prints. Mr. Spiller intends to follow the matter, as far as possible, into practice, and will shortly publish in our columns the result of further experiment. At present we can only say that the plan proposed seems full of promise, being sound in principle and singularly ingenious and simple in the mode of application ; and we shall look with the greatest interest for further developments of the idea. THE TEMPERATURE AT WHICH GUN-COTTON EXPLODES. A PARaGRAPII in our last, extracted from a daily contem porary, recorded an explosion of gun-cotton at the works of Prentice and Co., of Stowmarket. The explosion was at tributed to the combined heat of the sun and heat from hot air pipes, producing together, it was said, a temperature of 170 degrees, at which the gun-cotton exploded. On first consideration, the statement that gun-cotton exploded at a temperature of 170 degrees (Fahrenheit understood) is start ling enough, and some correspondence in the daily press on the subject has very naturally followed, in the course of which it is explained that in stating the exploding tem perature as 170 degrees, the word Centigrade should have been added. Messrs. Prentice write to allay the fears of some who were alarmed at the possibility of gun-cotton
