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THE PHOTOGRAPHIC NEWS Vol. XXXV. No. 1703.—April 24, 1891. CONTENTS. Mr. Sutton’s Block Process. page .. 313 EDITED BF course, indicate the use of a negative instead of a posi tive image in the initial operation, but that is a mere matter of detail. With this view, we sought to obtain a cast of the gelatine plate in the finest plaster of Paris. It was easy enough to pour the liquid plaster on the film, but, unfortunately, we could not persuade it, after hardening, to separate from it without partial destruction of the image. And even had this experi ment been successful, the necessary waxing of the plaster before immersion in the copper bath—so as to destroy its porosity—would most probably have de graded the finer lines of the picture. Our next experiment was more successful. We in the first place took a vigorous black-and-white negative from a line drawing, and from this a positive on a gela tine plate. This was developed, fixed, washed, and heated in the metal dish, according to Mr. Sutton’s method, the heat being continued in a moderated form until the film was bone dry. Still keeping it in the metal dish, we surrounded it with an edging of wood about half an inch in height. We now melted in a ladle half a pound of ordinary fusible metal, which liquefied at a heat of about 150“ Pah. Keeping this stirred with a stick of wood, so that its heaviest component, mercury, should not sink to the bottom of the ladle, we poured it carefully on the film. The result was encouraging, but by no means perfect, for the metal acted, to some extent, on the gelatine film, and made it granular, the granularity imprinting itself faithfully on the metal covering. We now took another positive which we had in readiness, and, after obtaining the relief as before and drying it, we placed upon it a trace of vaseline, and then rubbed as much as possible of the greasy matter from it with the palm of the hand. This plate was now warmed in the metal dish, and once more the fusible metal was poured over it. In about ten minutes surface crystallisation showed that the metal had solidified, andit separated easily from the film, leaving the latter quite un injured. From this metal plate we afterwards obtained an electrotype block, but we are not satisfied with the MR. SUTTON’S BLOCK PROCESS. We last week gave in detail the results of certain ex periments which we had made, and which were sug gested by Mr. Sutton’s paper on “ Electro-Photo- typy ” read at the Camera Club Conference. The results we obtained were of a negative character, but an experiment generally has the advantage of teaching something, even though the primary object in making it may not prove to be attainable. It was certainly so in the case before us. First we ascertained that, owing to certain differences in the manufacture of gelatine plates, some will, after development with pyro, stand a great amount of heat, even while the gelatine retains water and is in a swelled condition; but that with others the gelatine, on application of heat, will either contract or melt off the glass entirely. It would, per haps, not be difficult to trace the reason for this different behaviour in this respect on the part of certain well- known commercial plates, but it is not necessary, for our present purpose, that we should do so. We also ascertained that, in adapting Mr. Sutton’s process to line subjects, such as are ordinarily turned into blocks by the zinco process (some of which illustrate an article on another page), the gelatine film which had with stood the heating operation refused to bear the ordeal of the electrotype bath. One more observation noted was the fact that, as might be expected, the relief on the gelatine plate, brought about by the application of heat, was very much greater while the film remained in its swelled condition, than it was subsequently when the plate had been dried. This last observation made it at once obvious that, if we could obtain some kind of mould from the relief while in the latter condition, and in some material which would not suffer from immersion in the copper bath, so as to obtain a metal reverse from that mould instead of from the gelatine plate itself, a double advantage would be gained: firstly, in obtaining higher relief for the lines of the image; and secondly, in pre serving the gelatine from destruction in the copper solution. The interposition of this mould would, of The Professional Show-case from an Amateur’s Point of View, By Rev. F. 0. Lambert 314 A New Electric Lamp 315 Crystal Palace Exhibition 317 Technical Schools for Photography. By Max Jaffe 313 The Permanency of Photographs. By Fr. Wilde 319 Notes 320 The Second Triennial Exhibition at Gloucester ... Winter Photography. By Ernest II. Jacob Archaeological Photography ...J The Photographic Lens. By Thos. B. Dallmeyer Patent Intelligence Correspondence Proceedings of Societies Answers to Correspondents PAGE .. 322 .. 323 .. 324 .. 32G .. 327 .. 327 .. 327 .. 328