The photographic news

• Bandzählung: 7.1863
• Erscheinungsdatum: 1863
• 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-id1780948042-186300004
• PURL: http://digital.slub-dresden.de/id1780948042-18630000
• OAI: oai:de:slub-dresden:db:id-1780948042-18630000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

254 THE PHOTOGRAPHIC NEWS. [May 29,1863. seconds, all the details appeared to be out, but it remained very faint. I should say that my lens is a Boss’s orthoscopic, and I was working with full aperture. I made a print from a trial plate this morning, but had not time to tone or fix it; but as it may be interesting to you to see it, I enclose it. The negative was exposed forty seconds above lens, with full aperture: this was much blistered, but the development having been completed without any silver, no spots to transmitted light were formed, although by reflected light it is much spotted. Major Russell, in replying, first explains that in a recent communication, the object of recommending five parts of ether and three of alcohol, was to secure sufficient setting qualities in collodion made from ordinary samples of pyroxyline, as the effect of a bromide only is to retard setting. Equal parts of alcohol and ether may be used with advantage with a suitable sample of pyroxyline. The cotton we have generally used and recommended, namely, that made with equal parts of nitric acid at 1-420, and sulphuric acid at 1840, the cotton being immersed at a temperature of 150° Fah., Major Russell finds very sensitive but deficient in setting powers when a bromide only is used. In reference to the difficulties of “ Tyro Tannin,” above given, we make the following extracts from the Major’s communication:— I -will do my best to explain your correspondent’s difficulties, but cannot be sure about their cause, as so many things may produce the same faults. I was much interested in hearing his experience as I have been working quite alone, and have had no report of my method from any one except Mr. Glover, of Liverpool, who found it succeed well, and said that the gain in sensitiveness was even greater than I said. I regard your correspondent’s account and specimen to be very favourable, as the difficulties he complains of are very easily avoided, and he seems to be quite free from the only real difficulty in working with tannin—blurring and loss of distance with landscape subjects. I find that this difficulty is entirely avoided by the use of bromide alone. With regard to the difficulties, the gelatine solution was probably too strong. I never use it now stronger than 2} grains to the ounce : one drop of glacial acetic acid is quite enough, I find, for double this quantity. If much acid were used, and not well driven off by heat, the evil would be increased. The pyroxyline was probably of an unsuitable kind, intended for dry plates, and perhaps of such a kind as would make too thick a collodion with 5 grains to the ounce; samples vary greatly in this respect The tannin solution, perhaps, did not contain alcohol enough to penetrate, and the film might not be long enough subjected to its action to allow it to penetrate sufficiently, but the evil evidently commenced sooner. The fogging might be caused by the bath being impure, as one kept permanently acid is sure to be ; or by using strong solution of carbonate of amnonia, which is pretty sure to produce more or less fogging ; or very probably by light affecting its plates while being prepared. It is better to give a plan which will succeed well than to go deeply into the causes of failure, at least this course takes less time. Although the coating of gelatine will work well in my hands with bromized collodion and the alkaline developer, I think that the following plan is better in this case. When the glasses are cleaned make them pretty warm, aud paint thinly round the edges with a 2}-grain plain solution of gelatine. It dries as fast as laid on. When cold cover the whole with a very weak solution of india-rubber, or india-rubber and amber in chloroform and benzole : all this takes but a few seconds for each plate if many are done at once. After this, in my hands, the film does not move at all throughout the whole treatment. I find it best to keep the bath solution with carbonate of silver in the bottle, and, if necessary, to acidify after pouring out for use with a very small quantity of nitric acid. If the bath has been much used in an acid state it should first be made alkaline with ammonia and well boiled, or exposed for a few days to the sun, then filtered, acidified with nitric acid, and neutralized with carbonate of silver. This way of managing the bath will, I think, be found to be by far the best yet devised. Immerse the plate when perfectly freed from nitrate in an 8-grain solution of tannin in water, and a large proportion of alcohol, wash uniformly till oiliness disappears, and dry spon taneously. Great care must be taken not to expose the excited plate to even the most non-actinic light more than is necessary, as bromide is very easily affected by coloured light, and fogging is often thus caused. The best formulas for the alkaline developer I find to be as follows:— No. 1. Carbonate of ammonia G grains. Alcohol, 830 1} oz. Distilled water • ... 2} ozs. This may bo left mixed any length of time in a bottle. No. 2. Pyrogallic acid 1 grain. Alcohol and water in the same propor ¬ tion as in No. 1 2 drachms. This should bo freshly dissolved diluted from an absolute alcohol Solution. Pour on the dry plate enough of No. 1 to cover it, by tilting; two drachms is ample for a stereoscopic plate ; let it remain on some minutes, at least, then pour off and mix with one-fourth its bulk of No. 2, pour on so as to sweep the plate all over on tilting, as with an iron developer on a wet plate, for the image, if sufliciently exposed, starts out at once. Pour on and off a few times quickly, and then let remain at rest. If not too much exposed it will be come sufficiently intense in an hour or two, during which it requires no attention. If too much exposed it must be washed off quickly and intensified with pyrogallic and acid silver, but the film must bo well washed between the two operations—insufficient washing may have caused some of your correspondent’s troubles. On no account must more ammonia be added after the mixed developer is once on the plate, or fogging will be caused. I find that the pyro and carbonate of ammonia, when onco mixed, quickly loses force, so that if the same mixture is used in rapid succession on two or more plates, the first will always come out best. However the development is performed, it is important to have a largo proportion of alcohol in the liquid which first moistens the film to avoid risk of its becoming loose; if alcohol was not used it would account for the loosening. Your correspondent’s plan of using the carbonate of ammonia in strong solution is, I think, a very bad one, and nearly sure to produce fogging, as I said before. The pyrogallic should bo added all at once—subsequent additions after a few seconds’ development do no good. The pyrogallic may be used in larger amount, but I recommend that the strength of the carbonate ammonia solution be not exceeded. I hope I have given suffi cient explanation to enable your correspondent to avoid his difficulties, which probably rise from a combination of causes. The plan I have described answers perfectly well in my hands, and seems quite free from difficulties. I may add that I never recollect to have found the film tender under any circumstances when on gelatine. Although strong carbonate ammonia produces slight fogging, yet it might cause less than the proper method if the plates have been injured by light, as the strong alkaline liquid produces great intensity quickly, but makes the plate appear less exposed, that is, fails to bring out feeble impressions of light, whether made in the camera or out of it. I have no doubt that the great sensitive ness of the plates prepared with bromide alone, together with the sensitiveness of the bromide to coloured light, will causo difficulty when great care is not taken about light in the dark room. We understand that the second edition of Major Russell’s little work on the Tannin process is now in the press, and will shortly be published. It will doubtless contain much valuable information on this interesting subject. Scientitir Gossip. NEW SOLVENT FOR SILK—IMPROVED SPECTROSCOPE. In our former volumes we gave some notices of a process for dissolving cellulose (cotton fibre, &c.,) in an ammoniacal solu tion of copper. Several attempts were made to utilise the solution thus obtained in photography, and indeed in our