The photographic news

• Bandzählung: 13.1869
• Erscheinungsdatum: 1869
• 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-id1780948042-186900000
• PURL: http://digital.slub-dresden.de/id1780948042-18690000
• OAI: oai:de:slub-dresden:db:id-1780948042-18690000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Heft 545 (S. 73-84), Heft 547 (S. 97-108), Heft 589 (S. 599-610) fehlen in der Vorlage. Paginierfehler: Auf Seite 444 folgt Seite 443
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

able, but care should be taken to avoid those which readily fade, as most of those of organic character are apt to do when exposed to sunlight. We have tried Mr. Breese’s mode of making yellow glass, which consists in immersing a plate coated with plain collodion in a strong solution of saffron. This is a ready mode of improvising yellow glass, which is quite impervious to chemical rays ; but it has the disadvantage of gradually fading. AMMONIA FUMING AND VARNISHED NEGATIVES. A SOMEWHAT interesting discussion as to the effect which ammonia, when used to fume sensitive paper, produced on the varnished film of the negative, occurred at a recent meeting of the French Photographic Society. M. Chardon stated that after repeated employment of a negative with carbonate of silver paper, in which it is necessary to treat both the paper and the pads used in the printing-frame with the fumes of ammonia, the varnished film was found to be completely ruined; it has assumed throughout a yellow tint, which made further printing almost impossible. M. Schaeffner very naturally replied that ammonia fuming was not peculiar to the carbonate of silver paper, but was used by many photographers with ordinary albuminized paper; and added, that neither in his own somewhat lengthened experience, nor in that of others that he had ever heard of, had the ammonia produced any action on the varnish of the negatives. M. Davanne suggested that possibly M. Chardon’s nega tives might have been treated with a varnish containing gum benzoin, which was readily acted upon by ammonia. Shellac varnish, however, might be safely used, as films treated with it might be left in contact with liquid ammo nia for eight hours without becoming injured. We fear that neither the answer of M. Schaeffner nor that of M. Davanne quite satisfactorily meets the case. It may be perfectly true that carbonate of silver paper does not stand in a worse position than ordinary albu minized paper, if the fuming be used with the latter ; but if fuming be dangerous to the negative, it becomes objectionable under all circumstances, and the immunity of M. Schaeffner, and others he knows, does not afford much comfort if a possibility of danger exist. The know ledge even that the resin benzoin is most readily acted upon by ammonia does not quite meet the case, as the photographer generally uses a varnish of the composition of which he knows nothing. It may not contain benzoin, but it also may, and, therefore, with ammonia fuming he incurs a risk. We may further state that benzoin is a favourite resin with many manufacturers of photographic varnish. It is very soluble, very tough, very hard, and does not readily become tacky under the heat of the sun. It is sometimes used alone, and frequently added to varnish, in conjunction with other harder and more friable resins, in order to give toughness to the film. But we fear, further, that even the consolation offered by M. Davanne, as to the resistance furnished by shellac to the action of ammonia, is scarcely to be absolutely relied upon. M. Davanne is an able chemist and a trustworthy authority, and, in so far as shellac resists the action of ammonia better than most of the resins, his statement is doubtless correct. Shellac, however, is, like other resins, acted upon by ammonia, and dissolved by it. Indeed, in Mr. Johnson’s recent modifications of the carbon process, the cement used for single transfer is shellac dissolved in ammonia. This forms a capital cement, absolutely impervious to moisture when dry. But if liquid ammonia will dissolve shellac, it may readily be believed that prolonged or constant con tact with the fumes of ammonia may soften, and, possibly, decompose, the strongest and most perfect varnish. These considerations suggest the important question as to how far the practice of using fumed paper by some photographers may have contributed to the destruction of the negative films, of which we hear from time to time; and how far it may account for the failure, in some hands, of varnishes pronounced perfect in all respects by others. At present the records of experience are too scanty to furnish a basis for judgment, but we commend the sub ject to the attention of our readers. A VISIT TO SWAN’S CARBON PRINTING ESTAB- LISHMENT AT NEWCASTLE. BY A CORRESPONDENT. To make a journey of five hundred miles for the sole pur pose of witnessing the details of a photographic process might appear to some an undertaking of questionable wisdom, the more so, probably, from the fact that the pro cess inspected was neither new, nor recently improved by means of important modifications. In fact, the modus operands carried on was, except in one slight particular, exactly identical to that adopted by Mr. Swan at the outset of his labours. And yet the fatigue and expense of travel ling are well repaid, if by merely showing the spectator with what facility and certainty the process of printing in permanent pigments may be carried on. The method of manipulation I had often heard detailed, and the different stages of the operations clearly defined over and over again; but even the most concise statement of affairs could not divest my mind of the idea that the process must neces sarily bo an elaborate and complicated one, and it was not until I actually assisted at the performance of the several manipulations that I became fully aware of their simplicity. Indeed, to watch the progressive creation of the prints through the various phases cannot fail to produce in the mind of an eye-witness both pleasure and astonishment at the rapid manner in which the beautiful pictures are pre pared. Thus, the carbon process is one of those few things which appear simpler in practice than in theory, and which to see is to believe. The pictures which I had the pleasure of seeing prepared, under the kind guidance of Mr. Swan, were neither few in number nor of small dimensions, but large fifteen inches productions, printed and developed in rapid succession. Two of these, called “ The Snooze ” and “ The Truant," were from monochrome pictures, painted expressly for print ing in carbon, the copyright of them having been pur chased by the Autotype Company for publication by the process. The carbon prints of these two subjects are very fine, and, when carefully finished and tastefully mounted, will go far to render this style of reproduction a favourite one with the public. Besides prints of this description, all of which left nothing to be desired as regards tone, softness, and brilliancy, there was a copy from one of the most successful portraits in last year’s Royal Academy, that of a Scottish nobleman; in this instance, the original tint of the painting had been well imitated, and the texture of the velvet knickerbocker suit worn by the model was exceed ingly well rendered. The power of modifying the tint of the finished picture by altering the composition of the pig ment tissue is certainly one of the most valuable and plastic qualities of the process. The new modification recently introduced by Mr. Johnson, by means of which the transfer by india-rubber is avoided, has not yet been adopted at Newcastle; the Johnson method will, probably, supersede the old plan, but the latter is by no means so difficult as is generally supposed. Indeed, when the employment of the press is done away with, as it virtually is at present at Newcastle, in order to bring the india-rubber surface in absolute contact with the image, the process as it stands seems as simple as it need be. The developed image upon the india-rubber paper is thrown into a trough of cold water, and there placed in contact with a wet sheet of gelatine paper, taken out and pressed together, by passing over them a