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
• PURL: http://digital.slub-dresden.de/id1780948042-18680000
• OAI: oai:de:slub-dresden:db:id-1780948042-18680000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

THE PHOTOGRAPHIC NEWS. Vor. All. No. 492.—February 7, 1868. CONTENTS. The Elimination of Silver from the. Whites of Albuminized Prints 61 The Practice of Silver Printing 62 Visits to Noteworthy Studios 62 Critical Notices 64 Echoes of the Month. By an Old Photographer 64 The Action of Ozone upon the Latent Photographic Image 65 Hyposulphite of Ammonia and the Mixed Toning and Fixing Bath. By Nelson K. Cherrill 66 PAGE Vitrified India-rubber Sheet 66 Pictorial Effect in Photography. By II. P. Robinson 67 The Magic Lantern and Photography. By James Martin 69 Albumen Opalotypes 69 Proceedings of Societies—Liverpool Amateur Photographic As ¬ sociation—Oldham Photographic Society 69 Correspondence—Double Printing: Combination Negatives 7L Talk in the Studio 71 To Correspondents 71 THE ELIMINATION OF SILVER FROM THE WHITES OF ALBUMINIZED PRINTS. Although it may be impossible to secure the absolute stability of pictures formed of a metal like silver in an extremely minute state of subdivision, covered with an attenuated layer of gold, every suggestion which tends to increase the permanence of such prints must be regarded as a boon to photographers generally. Besides the sources of instability arising from carelessness in the process of fixing and washing, albuminized prints are, even when produced with the utmost care and skill, subject io two dangers : in the first place, the minute particles of silver forming the image are acted upon by sulphur and its com pounds, which are always more or less present in the atmo sphere. This is, however, a comparatively light matter, inasmuch as the colour of sulphide of silver, being dark, may modify the colour of the dark parts of the picture, but can scarcely obliterate or seriously aid in spoiling the picture. But the chief defect observable in a fading print is the loss of purity in the whites, which assume a yellow degraded tint, which robs the print of all beauty. If the print were perfectly fixed, no trace of silver should be left in the white paper, and it should not, consequently, bo subject to any change. The insoluble silver compound formed in the albu men, which hyposulphite of soda fails to remove, is the cause of this most serious defect in the print, and hence the vital importance of all experiments tending to its removal. The recent experiments of Mr. Spiller have shown that the hyposulphite of ammonia is much more perfect in its solvent action on this silver compound than the soda salt hitherto used. Unfortunately, there are difficulties in the way of introducing the ammonia salt into the market, of which the chief is the fact that it is so highly deliquescent that it would be difficult to keep in stock, to weigh out, and to deal with generally. How far these defects might be removed by modes of manufacture, should a general demand arise for the salt, remains to be determined. Before a demand can be created, the claims of the salt as a fixing agent must receive more extended examination, and its advantages be proved by further experience. Mr. Cherrill’s article on another page describes an interest ing experiment, and offers a most important suggestion, by the adoption of which the advantages of hyposulphite of ammonia may be tested, with very little trouble and expense, by photographers generally. Mr. Cherrill has, by adding sulphate of ammonia to the bath of hyposulphite of soda, converted, by a process of double decomposition, a portion of the latter salt into hyposulphite of ammonia. The test applied to the prints so treated furnished striking evidence of the superior fixing powers of the ammonia salt. Tested with sulphide of ammonium, the whites of the prints give the slightest possible evidence of the presence of silver, a very faint discolouration being perceptible, whilst the whites of an ordinarily fixed print, treated with the same sulphide solution, show a very definitely marked brown stain. Another print, in which a portion of the paper has been carefully preserved from any action of light by a perfectly opaque mask, shows in the whites no trace of silver what ever, after immersion for a quarter of an hour in a solution of sulphide of ammonium, which had altogether changed the colour of all portions of the print containing silver. Mr. Cherrill endeavours in his experiment to combine two distinct advantages. Besides securing more perfect fixation and the removal of silver from the whites, he aims to obtain the oft-coveted simplicity, certainty, and rich colour obtained in the old toning-bath of hypo and gold, with the immunity from mealiness, great reduction, &c., which attended it. Theoretically we see no reason why such a toning and fixing bath, when properly prepared, should fail to yield prints of permanency equal to those produced by the method at present in use. For those who are disposed to repeat Mr. Cherrill’s experiments we have one or two suggestions to make. In the formula employed by Mr. Cherrill, two drachms of sulphate of ammonia are added to the solution containing three ounces of hyposulphite of soda, by which nearly one fourth of the latter salt will be converted into hyposulphite of ammonia. We would counsel going a little further, and, instead of two drachms of sulphate of ammonia, use an ounce of this salt, which will convert nearly the whole of the three ounces of the soda salt into the hyposulphite of ammonia, and the full benefit of its solvent powers may thus be secured. The sulphate of soda which is also formed by the double decomposition will, of course, remain in the solution inert, and need not be regarded. In adding gold to the fixing bath, it should be re membered that as all crystallized samples of the chloride contain a little free acid, a slight decomposition will ensue, in which sulphur will be liberated. To avoid this, wo re commend that before adding the chloride of gold to the hypo, it should be dissolved in water, and five grains of carbonate of soda added to each grain of chloride of gold. Any slight excess of the soda salt, when introduced into the fixing bath, will cause the formation of a little carbonate of soda, the presence of which will be beneficial rather than injurious. A toning and fixing bath so formed will consist of a strong solution of hyposulphite of ammonia, hyposul phite of gold, a little hyposulphite of soda, and a little carbonate of ammonia. There is no reason why, in such a bath, perfect toning and fixation might not proceed at the same time. But there is this important caution to be observed : such a bath may continue its toning property long after its fixing powers are exhausted. If, therefore, it bo used for some time, the print should be immersed in a second fresh bath of hyposulphite of ammonia, and soda, made as