The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186800009
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
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• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

808 THE PHOTOGRAPHIC NEWS. [June 26, 1868. REMARKS UPON THE CARBON PROCESS As Practised in the Photographic Laboratory of the Royal Industrial College at Berlin. BY DR. H. VOGEL.* I.—Recent Experiments in Carbon Printing. Some time since I communicated the fact that I had been enabled to dispense with the use of gelatine in transferring carbon prints.t At the time I made known this modifica tion of the process, I myself had some doubt of its practical value, so incredible did the results appear ; but after eight weeks of continued experiment, during which time several hundreds of pictures have been produced and transferred without the aid of gelatine, the importance of this innova tion in the method has been fully established. The dis agreeable operations of preparing, filtering, and applying the gelatine solution, as likewise the delay involved by allowing the same to dry, the risk of the formation of air bubbles in the solution, and the difficulty of re-dissolving, are some of the time-taking operations which are thus avoided. On two occasions only did I experience a difficulty in removing the picture, after treatment with benzole some portions of the prints remaining attached to the india-rubber. In one of these instances I subsequently removed the picture by means of rubbing both sides well with benzole; but in the other I was not so successful, inasmuch as a portion of the print became torn during the operation of dissolving off the rubber. To obviate a recurrence of this difficulty, I dis continued the operation of dissolving, and placed a number of the prints in a dish under a piece of plate glass, pouring over them a quantity of benzol, and allowing them to become perfectly saturated with the same. The evaporation of the benzole was prevented by placing the vessel contain ing it into another larger dish, in which a certain quantity of water had been poured, and then covering over the prints with an inverted shell which dipped down into the water. After remaining immersed in the benzole for ten minutes, the pictures were dissolved off with the greatest ease. Recourse to this mode of proceeding need, of course, only be made when it is found impossible to dissolve away the india-rubber in the ordinary manner; but, in any case, very little benzole is expended in the operation. The reason of this occasional difficulty in removing the pictures lies in the quality of the india-rubber sheet and solution employed. It is not every description of rubber, even if it dissolves entirely in benzole, that is suitable for use, and it becomes therefore the duty of dealers in photo graphic requisites to obtain a material of requisite quality. If the rubber sheet and solution employed is of the proper kind, it is necessary merely to moisten the side of the rubber sheet with benzol in order to bring about a perfect separation. Another great advantage of the non-employment of gela tine is the guarantee it affords of the security with which the rolling-press may be used. When employing the method of transferring with gelatine I frequently had misfortunes with the roller, the pictures being crushed and thus rendered blurred and even quite worthless, and it was. for this reason that I had recourse, like Mr. Cherrill, to the screw-press. But without gelatine, manipulation with the rolling-press answers admirably; nor is there the slightest risk of accident to be feared from its use ; it is necessary, however, that the roller should be well fitted and perfect in every respect. The following will be found the most successful manner to manipulate :—On the steel plate I place a smooth piece of four-sheet cardboard, and upon this a square of cloth or felt; the white transfer paper, which has been immersed in water for about a minute and then quickly dried upon blotting-paper, is placed, together with the developed india- rubber picture, between the cardboard and the felt, and run through the machine. One single rolling operation is suf ficient, but the india-rubber picture should be pressed by * Photooraphischi Mittheilun^rn. t See page 200, hand evenly down upon the transfer paper before the piece of felt is placed over it and the operation of rolling takes place. For small pictures the screw-press is more convenient; the rolled pictures dry very rapidly, and may be treated with the tanning solution (chrome alum 1 part to water 300 parts) within half an hour of their being pressed. Instead of coating the picture with the alum solution, it is better to immerse it bodily into the liquid for a period of one minute, and then to allow it to dry in a temperature of about 15° Reaumur. In an hour the prints are ready for the application of benzol. One more advantage secured by the abandonment of gela tine in transferring yet remains to be mentioned. It is the possibility of being able to preserve the india rubber dis solved from the prints, and to utilize it a second time. II.—The Carbon Process without the use of Tndia-rubber. In the last number of the Mittheilungen I mentioned that I had been enabled to produce carbon prints with only one transferring operation, dispensing thereby with the employ ment of india rubber tissue. Expeiiments in this direction have likewise been made by M. Marion, of Paris; but that gentleman employs not ordinary paper upon which to trans fer his pictures, but albuminized paper, such as was suggested some four years ago by Henderson for the same purpose. M. Marion’s mode of proceeding is to lay the exposed carbon print in cold water, changing the latter frequently until the whole of the chromate has been discharged, and thus to bring out the image in relief. A sheet of albumin ized paper is then floated upon water (face uppermost), the carbon print is placed upon it, and both removed from the water at the same time, and pressed. A large number of prints may be placed one upon the other in this fashion, and the whole pressed in one operation. After being under pressure for about two hours the pictures are hung up to dry, and afterwards placed in a hermetically closed vessel, where they are exposed to the action of steam. By this means the albumen becomes coagulated, and there remains nothing further to be done than to develop the prints more fully, and to wash them in warm water, the picture, of course, remain ing firmly attached to the albuminized paper. The image is, however, reversed. Although the albumen is unnecessary as a cementing material, I was of opinion that, on account of the homo geneous and brilliant surface which it presents, its employ ment presented many advantages over ordinary paper. For this reason I instituted a trial of this transferring process with albumen, although I went to work on a different plan from that pursued by M. Marion. The albuminized sheets were first coagulated and immersed in water, then blotted upon filtering-paper, and passed through the roller, together with a dry carbon print, in the same manner as when mani pulating with ordinary paper; after drying for about an hour, the pictures were placed in cold water for a like period to develop, and subsequently in warm water. The pictures developed well, and with fewer air-bubbles than when ordin ary paper was used. They possessed a certain amount of brilliancy, and had somewhat the appearance of silver prints upon albuminized paper, but they did not possess the beautiful glossy black tones presented by carbon prints produced in the ordinary way, and the whites were certainly less pure than those of prints transferred upon ordinary paper. At the same time, the pictures on albuminized paper exhibited less tendency to tear than the others. The transfer process is always best conducted (if either albuminized or ordinary paper is used) by having the trans fer paper of somewhat smaller dimensions than the carbon print, so that the latter may overlap on all sides to the extent of a quarter of an inch. I likewise essayed the transfer of the exposed carbon tissue, after saturation in water, to dry coagulated albuminized paper, but found it difficult in this case to avoid creases in the picture, a difi- culty, however, which is overcome by previously moistening the albuminized paper.