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
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• 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

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• Strukturtyp: Ausgabe

2, 186- whlCj r occt re ng fe spobdel the X, ime2/ v tbo" he‘a5 he"2e remocbes letaib 1 ibtain S05 and 80 ough W u askw : in albdy nen isagr, • the c0M Ve do »* icy have ie additi. icy to fog id being J • addition ducing C most soj 5 on the semi-pr’P can fort’ ents ita f which, y in obt don varl, nd the J 30s. to ’’ cilities j .nd and at ther d be noK • propen" od 5001 led nerally" under ease 0 9 you ar the defeb lore sidg ence il J >, will' ( ivisef opof3 n ina5 conned”) t° cutSi ny m5 it ot«7 of tbel •y platbe f on>< gthen"7 r lens' 5 I t of tb] aybeutd non W 2 io mal prit0%, t one o!2 hall De «compo“ t wit maper 0, ■aplW/ ™t thel 00 ind 11 3 00- ourett’ THE PHOTOGRAPHIC NEWS. Vol. VI. No. 192.—May 9, 1862. HOT DEVELOPMENT FOR DRY PLATES. A SIXGULAR discrepancy appears to exist in the experience of different photographers as to the value of hot developers, especially in their application to tannin plates. For years past, heat has been used by Mr. Mudd and some others with collodio-albumen plates ; but in the hands of the majority of photographers using other processes, it has not been uni versally, or even, we believe, generally successful. In our hands, with collodio-albumen plates, it has been completely satisfactory, as it has in all cases of which we have any de finite information; but have no reason to believe that it has ■ been largely adopted. The announcement of its amazing effect on tannin plates in America has given a fresh impetus to experiments in that, direction, and the results, as we have stated, present considerable discrepancy. Mr. Sutton recently tried hot deyelopment with tannin plates, and states that the films split up, entirely spoiling the negative. Mr. England, some weeks ago, stated a similar result as attending his efforts with hot development. More recently he informs us that, getting over that difficulty, heat in his hands always produces fog. Amongst the American operators there arc some who state at their meetings that they have utterly failed in obtaining the results described, whilst the majority, however, have been entirely successful. There can be no doubt that for these discrepant results there is a cause, and the conditions have varied in some way at present un explained. We have been during the last few weeks experimenting at intervals with hot development, and have arrived at some conclusions which may be of service to our readers in their own operations. We may remark at the outset, that we have been some what disappointed in the results. We have found un questionably that the time of exposure may be considerably reduced when hot developers are used, but there are other difficulties which go far to nullify the advantages. The splitting of the film we have found no difficulty in obviating by the use of suitable collodion ; but we have found in all cases that where great heat is used, and free nitrate of silver is present, that there is considerable tendency to fog or surface 'eduction, and that in the conditions in which we have Morked, this difficulty was sufficient to nullify the value, in other respects, of heat. This is a difficulty which we have 110 doubt can be met, but a little care and further experi- ment will be necessary to settle the precise conditions. . The first plates on which we operated in our recent expe- iments were prepared with caramel, and forwarded to us by a correspondent some months ago. We obtained with them fully detailed pictures with a very short exposure; but in all cases there was a certain amount of red fog, which appeared chiefly at the edge where the plate had drained. W c concluded that some traces of free silver had been left at this edge, and that as the plates had been kept about five months, decomposition had set in. We have since been led to the conclusion that this result was considerably aided, if not entirely caused, by the effect of heat. We have since then tried hot development on simply washed plates; plates treated with gallic acid; plates treated with gallic acid and honey ; and plates treated with tannin and honey. In each of these cases heat has proved a decided accelerator, but it has also, unfortunately, produced moreor less of fogging, or general surface reduction. The 08 thus produced may easily be removed, it is true, by means of a camel-hair pencil, as it lies loosely on the sur- lace of the picture ; but this is a makeshift which ought I not to be needed. We have a full conviction, however, that this is to be avoided entirely without losing the advantages of hot development, a conviction which we hope to verify shortly by further experiments. We may just briefly hint here, what appears to us to be the source of the discrepancy between the successful and unsuccessful experiments in this direction. In the various incidental allusions of the successful operators in America to the conditions under which they work, we find that very old collodion, with plenty of free iodine, and an acid silver bath are used. These, as we know, are very potent agents in preventing fog. In our own experiments we have used a variety of collodions, some new and colourless, some a few months old, and one two years old ; but all sensitive and not containing more free iodine than is indicated by a lemon tint: and the silver bath has been nearly neutral, having only the faintest trace of acetic acid. Mr. England’s operations are, we believe, conducted with chemicals in similar condition. He, moreover, redips the plate in a silver bath before development, and the application of a hot developer under such circumstances, is almost certain to produce at once the surface reduction to which we allude, and when that is commenced, development rarely progresses favourably. It is probable, that in the use of an old collo dion and an acid silver bath, the conditions will be found which admit of the successful application of hot developers. • THE HONEY AND TANNIN PROCESS. Some experiments we have recently made with tannin and honey have been most successful and gratifying, both as regards the quality of negative, and the sensitiveness and certainty of the process. In sunlight, an exposure of seven seconds, with a lens of six inches focus and half-inch aper ture, has produced a good negative of buildings and foliage. The negatives are of very fine quality, and the prepared plates, notwithstanding the use of honey, quite dry and free from stickiness. In the preparation of the plates we followed Mr. England’s instructions, but tried a variety of different collodions, the results of which we will briefly state. We first made a collodion of the pyroxyline used by Mr. England, a sample of which he had favoured us with. It is evidently made at a low temperature, three grains giving a collodion of quite sufficient body, which yields a tough, skinny film, easily removed from the plate without tearing. This was iodized with three grains of iodide of ammonium, and three grains of bromide of cadmium. The plate became in the silver bath very creamy, and worked exceed ingly well at once in the wet state, giving a clean, brilliant, dense negative with very short exposure. When prepared with the honey and tannin, it yielded good negatives with an exposure of about eight or ten seconds in sunlight. The film had a tendency to loosen, but with care was not lost. We next tried a sample of commercial collodion of high repute for the wet process, which is generally believed to be iodized with cadmium, and to possess no bromide. This gave a clean, good quality of negative, but was much slower; with an exposure of twelve seconds it was not more than half done. A sample of collodion prepared by Mr. Sebastian Davis, according to the formula he recently described at a meeting of the South London Society. This gave exceedingly satis factory results in every way, and was scarcely inferior in sensitiveness to the first mentioned. We next tried some plates with a sample of collodion