The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• 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-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite 1-72 fehlen in der Vorlage. Vorlagebedingter Textverlust.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

THE PHOTOGRAPHIC NEWS. 92 [Feb. 21, 1862. meats was, that cotton was out of all proportion the best. True, there were some persons who still preferred paper ; but the pre ference was generally based rather upon experience than any theoretical superiority. Next came the question of acids. We knew that nitric acid alone would produce the desired result; but it was much more manageable and satisfactory to use the mixed acids and water. The use of nitrate of potash used to be very common, but it had now fallen much into disuse, on account of the difficulty of getting rid of the sulphate of potash formed. He had been a little surprised to hear that it entered into Mr. Davis’s formula, and should be glad to know the espe cial ground upon which he used it. Of course, in speaking of nitrate and sulphuric acids, we only meant solutions of the anhydrous acids, and it was convenient in practice to use them of such a strength as admitted the addition of water, which, by generating heat, gave them a suitable temperature. Next camo the proportions of acids. Mr. Hardwich had tabulated the results of almost every proportion, from three of nitric acid to one of sulphuric, to three of sulphuric to one of nitric. The maximum of nitric acid gave a film in which there was very little contrast; whilst with excess of sulphuric the pyroxyline gave a film yielding a vigorous intense image. Experience alone could decide upon the desirable medium. The question of tem perature came next, that entirely depended upon the quality of pyroxyline desired, and upon the strength of acids used. With strong acids a high temperature was necessary; whereas, if much water were added to the acids, a much lower temperature would produce a similar result. The time of immersion would also be affected by similar causes. He remembered that Mr. Hadow, some years ago, spoke of leaving the cotton in the acids all night; that would, of course, be at a temperature of about 60° Fah. At the temperatures now generally used, about ten minutes seemed to be regarded as sufficient. Mr. Hughes proceeded to refer to the use of nitrous acid and its general abandonment, and to the importance of thorough washing, and the advantages of an alkali wash in neutralizing any remain ing acids. The strengths and proportions of the solvents were next passed in review, and the importance of considering them in relation to the quality of the pyroxyline and the size of plates intended to be used. Coming to the question of iodides and bromides, and the undoubted advantage of the latter in con junction with iron development, he remarked on the singularly large proportion of bromide used in America compared with what could be used with advantage in this country. Regarding the uso of chlorides in collodion he had recently been going through a series of experiments in this direction. He had come to the conclusion that the smaller the proportion the better the result, and the entire omission was best of all. Mr. Simpson said Mr. Hughes had throughout his remarks enunciated a principle of the utmost importance in every branch of photography, namely, the importance of harmonious relation in all the parts of any process. It was almost im possible in photography to speak of the advantage of anything per se, as that which was of the utmost value under certain circumstances might be useless under other conditions. Never theless it was possible to fix those conditions, and as Mr. Hughes in his able review of the various processes employed in the manufacture of collodion, might perhaps have left an im pression on the minds of the uninitiated that its successful manufacture was almost a hopeless task, involving as it did, so many considerations, he thought it might be desirable briefly to state a method in which all the conditions were tolerably well defined, and which, he believed, with ordinary care, would always give satisfactory results. The method of preparing the pyroxyline was an old one, if ho remembered rightly, first published in the definite form, in which he should state it, by Mr. Sutton. He took equal parts by measure of sulphuric acid and nitric acid ; the latter of a specific gravity of 1420, the former the oil of vitriol of commerce. These were raised to a ’ temperature of about 150° by placing the vessel containing then in another containing hot water. The cotton wool was immersed man to make some definite arrangements, enter into particulars i of detail, &c., and I am enabled to announce that we were met < with ready courtesy regarding all our proposals, and that i negociations are pending which will, I hope, issue satisfactorily i both for this Society and all persons interested in the progress < of photography throughout the world. The necessity for an < auxiliary exhibition needs no urging: among photographers, we t have reason to believe that it is universally felt, and the simple i fact that photographs have been prepared for exhibition in all < parts of Europe by those who have either received no allot- i ments of space, or have been grievously disappointed in the 1 small portions set apart for them, lead us to hope that a collec- ; tion may be gathered together, which, for quantity, quality, < variety and interest, will probably surpass any exhibition : organised under less rare and peculiarly favourable conditions. ] The opportunity is not likely to be again preferred for many : years to come, and your Committee trust that the personal i exertions of every individual member will aid them in doing • justice both to it and the art we represent. We are anxious to : embody all the more recent improvements and discoveries in the art, to illustrate fully the capabilities of different processes, and to show, in various ways, and as completely as possible, all the various applications of photography, to exhibit select speci mens of choice or novel apparatus, and, in short, to carry out all suggestions which will tend to raise the art as art in public estimation, and at the same time give the collection a full share of scientific interest, and great educational value. Mr. Sebastian Davis then read a paper “ On the Manufac ture of Collodion ” (see p. 79). At the conclusion of the paper Mr. Davis produced various samples of pyroxyline, illustrating the effects of strong acids at a low temperature, and of weak acids at a high temperature. A sample, also, made after the formula recommended by Mr. Davis was shown, and a portion of it added to a mixture of alcohol and ether. It dissolved almost immediately without appreciable residue. The CHAIRMAN, in proposing a vote of thanks to Mr. Davis, referred to the great value of such papers, involving, as they did the careful prosecution and accurate recording of important chemical experiments. Mr. Simpson, referring to the remarks in Mr. Davis’s paper, suggesting the possible accelerating qualities of various organic and other compounds of silver, said, if he remembered rightly, the arsenite of quinine had been used in some of the earliest experiments with collodion. Dr. Diamond had shown him a very early collodion positive, in which there were very distinct traces of five separate tints obtained. The collodion by which it was obtained contained the salt just named. Mr. C. J. Hughes remarked that, notwithstanding the in creased commercial facilities of procuring good working collo dion, without the trouble of each photographer preparing it for himself, the subject was as important as ever; and, notwith standing all the research which had been made, we did not possess that amount of certain and definite information on the subject which we felt we ought to have. The matter appeared simple enough, perhaps, but no one could grasp the whole sub ject, but those who had had very large experience in every phase of making and using collodion. There were many causes which contributed to render certainty on this subject very diffi cult to obtain : the intangible chemical composition of some of the elements involved; the trembling state of balance upon which the best conditions depended, and the relation and in fluence which other things, such as the bath and developer, had in affecting results, all contributed to render the subject a difficult one. Those only who had by experiment realized these diffi culties, could properly appreciate the value of a paper like that of Mr. Davis. The subject was wide enough for many even ings’ discussions. First, there was the cotton wool and the various substances which had been proposed as substitutes, such as linen, flax, paper, and even silk. Mr. Hardwich had given these substances much attention, and the result of his experi and kept in about ten minutes, washed well, and dried. Fiv« or six grains of this would dissolve entirely in equal proportion 8 of ether and alcohol, the latter of a specific gravity of -820' Equal parts of iodides of cadmium and sodium were used in iodizing. Ho preferred the latter to potassium, as being mor 0 soluble. About half-a-grain of bromide of cadmium and tw° grains of each of the iodides named, gave a collodion very sensi tive and very stable, and yielding most excellent results witb iron development. For the tyro he knew of no formula s0 simple; whilst for most purposes ho knew none giving finer negatives. , Mr. HANNAFORD found the formula Mr. Simpson had just described a most efficient one; and by adding different qua”' tities of water to the acids, he obtained pyroxyline of an! quality he required, for wet or dry processes. By adding 11 little water to the acids named, and raising the temperature 10 about 160°, he obtained a pyroxyline giving great intensity’ and by adding sufficient bromide, ho could regulate the result' As to the use of a chloride, he thought that might be useful 1a a collodion for dry purposes, as it was now generally understoo that th the iod plates, phers f that h pyroxy obtain! 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