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

378 THE PHOTOGRAPHIC NEWS. [August 7,1863. * Prom Humphre^t Journal, 200 parts. 1 part. 10 parts. diaphragm the exposure will be— For a lens with 4 inches focus, 100 parts 3 » 5 .. 100 parts 8 „ 2 „ is formed of Distilled water Tannin Alcohol ... Distilled water Crystallized nitrate of silver Glacial acetic acid solution:— Distilled water .. Pyrogallic acid .. Glacial acetic acid 5. Exposure. The autopolygraph we employ is furnished with a simple quarter-plate objective; with the smallest The operation is conducted as follows: the sensitising bath may contain two plates at once, a light border of gutta percha separating them, so that one plate cannot slide upon the other. While we are collodioning a second plate, the first is sensitized, and when the second is put into the silver bath, withdrawing the first, which is immediately put into the first washing bath, and so with the rest. The first operation is thus performed rapidly and in good condition. 3. The Washings. As the plates are withdrawn from the sensitizing bath, they are placed in the first bath of filtered distilled water, where they must remain until the greasiness disappears. When the twenty plates of the autopolygraph are collected in this bath, they are passed successively, one by one, into two other baths of ordinary filtered water, and, lastly, in a fourth bath of distilled water, also filtered. When all the plates have been collected in this last bath, and we are about to apply the preservative solution, a light stream of distilled water is poured over each plate, in order to re move the last impurities that may still adhere. For these washings we employ rectangular zinc dishes, covered internally with a coating that cannot be attacked (manufactured by M. Deltenre). The middle of the dish is occupied with a raised partition, so that it forms a sort of continuous channel upon the edges of which the twenty plates rest. The dishes are 24 inches long by 8 inches wide. 4. Application of the Preservative.—The tannin solution by a fresh quantity of the original developer. At the conclusion of these manipulations, longer and more difficult to describe than perform, the plate is carefully washed, and fixed as usual, but with hyposulphite of soda. After washing, a coating of gum-arabic solution is applied, and when the plate is quite dry, it is varnished. The nega tive is now finished. As the reader may now judge, the process is far from being difficult or complicated ; and success is pretty certain. And we again urge amateurs to try it. If they carefully follow the directions here given, it is quite certain that their efforts will be successful.—Bulletin Beige de la Photo graphic. MACROPHOTOGRAPHY, OR THE ART OF TAKING ENLARGED PICTURES OF PHOTOGRAPHS* TIE NEGATIVE FOR ENLARGEMENT. The size of the negative will have to depend on the diame ter of the condenser; if this be nine inches, a one-sixth plate will be large enough, the object being to get the negative as 1 to 14 minute. 2 to 21 minutes. 3 to 3 } do. It must be continually shaken to avoid deposits. The most delicate part of the process now begins, at least under certain circumstances. The development may exhibit three distinct characters :— 1st. The proof comes out well; the whites well preserved, and all the details distinct and clear; we have then only to add gradually a few drops of a weak solution of nitrate of silver, so that the blacks may assume the intensity required in a good negative. 2nd. The picture comes out rapidly, with a tendency to fog ; it has been exposed too long. We then add a few drops of acetic acid, without nitrate, to check the development. Towards the end, add, if necessary, a little silver, to bring the picture to the desired tone. 3rd. The picture comes out slowly ; the large lights only are distinct; there is no detail; the exposure has been insuf ficient. Then add to the liquid in the dish two or three drops of a concentrated alcoholic solution of pyrogallic acid (for example, one drachm to ten of alcohol, which serves very well for the preparation of the strengthening solution in the wet collodion process) ; add, also, one or two drops of a weak solution of silver, and allow it to act. If the addition is insufficient, increase the dose until the details come out, then strengthen, if necessary, by adding acetic acid and silver. During this operation it may happen that the liquid be comes muddy; it must then be quickly rejected, and replaced To prepare it we put the tannin into the water and it is generally very quickly dissolved; then it is filtered several times, three or four at least, and, lastly, some clear alcohol is introduced into the liquid. The object of the latter is to make the liquid penetrate the collodion film more readily; it also aisists in making the solution keep longer without decom position. It should be noted that the alcohol must not be added until the solution of tannin is filtered, for the alcohol dissolves certain resinous substances always found mixed with tannin which are insoluble in water. We then take two lipped glasses, of very different forms, and numbered, so as not to confound them with each other, and pour into each a certain quantity of the solution of tannin. After the first bath, withdrawn from the last washing bath, and rinsed with a stream of distilled water and drained, we pour upon it several times the contents of the glass No. 1 until the liquid has well penetrated the film, that is to say, until it has covered all parts of the plate equally ; next, this tannin application being complete, the plate is drained, and then the contents of glass No. 2 at once, and the excess is poured off into glass No. 1. We then put the plate to dry, collodion side downwards, resting by one corner on a piece of blotting-paper. But according to the recent experiments of MM. Teissere and Jacquemet, the sensitiveness of the plate is greatly increased if after having poured on the tannin the plate is washed in a stream of distilled water, so as to free it from the excess of tannin. It is important not to touch the collodion or the silver bath with the fingers more or less soiled with tannin ; to avoid any accident, it is well to first sensitize all the plates, before proceeding to the application of the tannin. After drying for seven or eight hours, under the ordinary conditions of heat and moisture, the plates are ready for use. They are then placed in the upper chamber of the autopoly graph, or in a grooved box, hermetically closed. The sensi tiveness of these plates continues a very long time, as much as two or three months, but they eventually become mouldy. 2. Sensitizing. The silver bath to sensitize the collodion plate is composed as follows:— 5} do. 74 do. Do. do. Do. do. C. Development. It is important to delay the development as little as possible, for the plates quickly lose the faculty of retaining the image. Here, if we do not deceive our selves, is the starting point of a theory explanatory of the formation of photographic images, the principle of which was first announced by M. Vidal. Before commencing the development, the edges of the plate must be coated, by means of a small pencil, with a very dense varnish, composed, for example, of—alcohol, 100 parts, shellac, 20 parts ; two coats must be applied. After drying, each plate is immersed for a few moments in water, and afterwards uniformly moistened with the sensitizing solution. The plate is next immersed in a flat dish con taining a sufficient quantity of the following developing