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THE PHOTOGRAPHIC NEWS. VoL. XXVII. No. 1314.—November 9, 1883. CONTENTS. Scamoni’s Electrotype Method of Reproducing Photo-reliefs ... 705 Development—Should the Developing Dish be Rocked, or Not? 706 The Production of a Constant Supply of Oxygen by the Action of Light on Growing Vegetable Organisms 707 The Photographic Exhibition 707 Among the Mountains with a Camera. By Professor W. F. Donkin, M.A , F.C.S 709 Parker’s Sky Shade. B; Norman Macbeth, R.S.A 710 Enlarging on Argentic Paper and Opals. By A. Goodall 711 PAGE 712 714 715 716 716 718 719 720 720 Notes Lessons in Optics for Photographers. By Captain W. De W. Abney, R.E.,F.R.S Patent Intelligence How to Glaze Photographs. By E. Wideman Correspondence Proceedings of Societies Talk in the Studio To Correspondents The Photographic News Registry SCAMONI’S ELECTROTYPE METHOD OF RE PRODUCING PHOTO-RELIEFS. The question of producing photo-relief plates for photo gravure and other mechanical printing methods is one that is occupying considerable attention just now. The most promising way of utilizing the relief of the photo graphic image is to use the electrotyping process, and this is, in fact, done in the case of the most successful photo graphic printing blocks. The relief may be built up upon the photographic image by placing this vertically or hori zontally in an electrotyping bath, and either the Poggen- dorff or Smee battery, or the thermo-electric battery of Clamond, as well as the dynamo-electric machine, may be used in the process. M. George Scamoni, the director of the photographic establishment in connection with the Russian State Paper Office, produces his heliographic plates by electrotyping in the manner following. He employs, and has done so for years past for plates of medium size, an electrotyping trough measuring four feet long and eighteen inches in breadth and height. The trough is made of wood, and is fitted up as shown in the accompanying sketch. a, The top of the perforated zinc element; b, The clay porous cell; c, Connecting wire, covered with rubber solution to insulate it, except where it is brightened at the ends. One end is made fast to the perforated zinc at a, and the other is placed carefully in contact with the relief plate, d, the plate being coated with wax and graphite; e is the lattice work at the bottom of the battery. The wooden sides and bottom are lined with lead, and then covered with a hot mixture of old gutta-percha and pitch, the film of the latter being about a quarter of an inch thick, and applied carefully and uniformly. One inch from the bottom of the trough is a lattice, which is kept in its place by leaden weights ; under the lattice the impurities of the bath accumulate. The strength of the sulphate of copper solution should always be maintained from 35 to 38" Baume,* and to en- In the case of new apparatus, the sulphate of copper solution is often " mr Ereater Strength than 19 to 20° Baume, and then it is usual to add acid is. su P huric acid as will raise one or two degrees. Unless sulphuric reddish aded In this way, the copper particles precipitated are of a powdery "eudtsn-brown character, and mill not bind. sure this strength, some perforated vessels of lead are placed inside the trough full of sulphate of copper crystals. If it is found that the deposit on the edges of the relief plate is the reddish-brown amorphous copper instead of the flesh-coloured metal, this is a sign that too much sul phuric acid, impregnated with zinc, has come from the porous cell into the copper solution. In this case there is no help for it but to pour the fluid into a wooden tub and to add powdered chalk so long as any effervescence is perceived. After treatment in this way the liquid is well stirred occasionally during a few hours, and permitted to rest through the night, when it may be filtered and poured back into the electrotyping trough, and brought up to its proper strength by the addition of more sulphate crystals. The porous cell, which contains well-amalgamated zinc, should shortly before use be filled with sulphuric acid of 2} to 31 Baume, and according to the size of the plate to be electrotyped, two or four such cells are placed opposite one another, the top of the relief plate should coincide with the top of the zinc. If, as is required in the treatment of delicate gelatine reliefs, the whole surface of the plate is to be quickly covered with precipitated copper, the porous cells should be replaced during the day with others, duly rinsed in water and freshly filled. Moreover, the ends of the wires must be maintained bright by frequent rubbing with emery cloth. The plates to be electrotyped, before being put into the trough, should be rinsed uniformly with strong spirit, so that the formation of air-bubbles is avoided, and then as quickly as possible immersed in the solution, and the wires connected up. If a plate has already received a deposit of copper over its surface, then, before a second treatment in the electrotyping trough, it should be rinsed, and lightly brushed with dilute sulphuric acid to facilitate the binding of the new deposit of copper. Sometimes certain parts of the surface of a plate are a long time getting covered, and an oxidizing action is set up ; in this case some little attention is necessaty. The plate is raised from the trough in a horizontal position and covered with a sheet of blotting-paper dipped in the sul phate of copper solution, a piece of the blotting-paper being torn off where the defective parts are, and these bare gelatine portions carefully dried with tissue paper. These same defective parts of the plate are then carefully covered with a solution of rubber in benzole. After this varnish has dried—it dries very rapidly—more graphite is applied, by dabbing carefully with a muslin bag containing this powder. The whole operation must be conducted with the greatest care, so that the surface afterwards has the ap pearance of a perfect mirror. The finest Siberian graphite, which has been rendered a