The photographic news

• Bandzählung: 13.1869
• Erscheinungsdatum: 1869
• 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-id1780948042-186900000
• PURL: http://digital.slub-dresden.de/id1780948042-18690000
• OAI: oai:de:slub-dresden:db:id-1780948042-18690000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Heft 545 (S. 73-84), Heft 547 (S. 97-108), Heft 589 (S. 599-610) fehlen in der Vorlage. Paginierfehler: Auf Seite 444 folgt Seite 443
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

JANUARY 1, 1869.] THE PHOTOGRAPHIC NEWS. 7 dipping-baths, with a dipper in each, to receive plates from silver bath as fast as ready. In this way plates would be brought direct from the silver bath and placed on the dipper in No. 1, and worked up and down a few times; then, when another was ready, No. 1 would go into No. 2 ; when a third was ready the second would go into No. 3, and so on, putting each plate into No. 1, and then into either of the other spaces till all were full. Next begin by taking out the plate from No. 2, holding under a stream of clean water for a minute; then coating with two lots of tannin, the first thrown away, the second kept to act as first for next plate. I made the box myself with common deal, and gave it three or four good coats of shellac varnish ; the pipes are gutta-percha. But the washing is by no means the only cause of pinholes. Nothing can be much worse than the horrid tin boxes sup plied as travelling-cases for plates; the poor plates go jogging up and down the whole way, rubbing off no end of little bits, from the size of a cheese-mite to the size of the piece he puts in his mouth ; anil these are the causes of those patches of pinholes all near one part of the plate so often seen. Carry your plates packed in paper, and only put out one day’s work at once, and that into dark slides, or a wooden box that has had half-a-pint of thin glue shaken up in it before using, and allowed to dry well, and so retain any loose particles. The plates in this box must be well padded, so as to prevent all movement. Another cause of very small pinholes all over the plate is using one bath for many plates in rapid succession. What the precipitate is 1 cannot certainly say ; but I have often found something like flue or light-grey dust at the bottom of a bath on the morning after use. Always use three or four baths, and do not prepare more than twelve or twenty plates in any one bath on one evening. The precipitate is in the form of needledike crystals, and is not iodide of silver, as I once diluted my bath so as to make it very milky with iodide, and a plate prepared in it was perfect. ON DRY PLATE PROCESSES. BY A. DE CONSTANT.* In a former communication I have spoken of the old gum dry process made known several years ago by M. Thomas Sutton. In forwarding you specimens of this process, I laid particular stress upon its rapidity, as also upon the delicacy and atmospheric perspective exhibited in its results, all of which were peculiarly fine. As I alluded to the process, however, merely as accessory to, and in compari son with, Mr. Baratti's coffee process, I did not then make known all I knew respecting it, and propose therefore to complete my remarks upon this occasion. The rapidity of the gum process appears to me to surpass that of all other dry plate methods, and when employed with certain modifications it will, I feel sure, rival the wet process in its sensitiveness. This special quality of gum to impart rapidity is so conclusive that when a solution of that substance is added to any of the slow-acting preserva tives, increased sensitiveness is at once imparted. Unfortu nately, as in all good things, there are some drawbacks to its employment, and the simple gum dry process is beset with several serious inconveniences, the principal one being its great tendency to rise from the glass ; small blisters are formed over the surface of the film, which assumes the appearance of a toad's skin, a result which is sometimes unavoidable even by carefully imparting to the plate pre liminary coatings of the best description. The preservation of plateis prepared by the ordinary gum dry process is like wise a matter of some difficulty ; I have, it is true, kept some for several weeks in a moderate temperature, but, when — ■ ■ — * Read before the French Photographic Society. subjected to considerable heat, the change is very rapid : marble-markings and solarized effects of the most extra ordinary description being produced. Lastly, the tendency of the gum to absorb moisture necessitates the precaution of employing such plates only whose surfaces are perfectly dry. I have experimented with the gum process without sugar, with white sugar, with sugar-candy, and with boiled syrup of gum, and I have always suffered more or less from the inconveniences I have mentioned. Nevertheless, with syrup of gum prepared in certain proportions (which possesses the advantage of furnishing a solution always ready for use), I have obtained satisfactory results as regards the solidity of the film ; but boiled syrups, I find, exert a specially inju rious effect upon the plates after preservation for a few days, by reason of the formation upon the film of minute crystals, which are very tenacious, and resist altogether the action ot washing. These crystals give rise to minute spots upon the sky of the negative in the form of circles or stars, defects which, in my opinion, will have the effect of banishing boiled syrups from among the list of ingredients suitable for the preparation of dry plates. Sugar simply dissolved does not possess the disadvantages above alluded to, and the addition of sugar-candy to the gum process, as proposed by M. Manners Gordon, which has the effect of rendering the results more vigorous and bril liant, must therefore be considered as an improvement. This modification of the gum process does not, however, constitute the whole of M. Gordon’s dry plate method, which he has endowed with two special improvements, viz., the addition of gallic acid to ensure better keeping qualities, and the employment of iron development, which, by reason of its astringent character, prevents the rising of the film. Thue, the endowment of the film with solidity, security, and good keeping qualities is the result, brought about by M. Manners Gordon's modifications, for in proceeding according to his formula we are certain to produce nega tives which have all the appearance of good plates obtained by the wet process, and which are scarcely to be distin guished from such even by the most practised photographer. What more can be desired? will be asked. At the risk of appearing ridiculous, I would timidly assert that for repro duction of distance, perspective, and natural tints, and for other artistic considerations, I prefer the results obtained with certain dry collodions to those furnished by the wet process. For this reason I am one of the first to appreciate the valuable improvements which have been effected by M. Manners Gordon, and it is in order to make the process as widely known as possible, as also to correct an important omission which occurred in the formula published in the bulletin for September last, that I have chosen to speak on the subject on the present occasion. According to my experience, I have found that the addition of gallic acid prevents solarization, regulates the development, and endows the plates with great preservative qualities, both before and after their exposure, facts which have been confirmed by a recent communication of M. Gordon’s. Count Nostitz, in a paper read before the French Photographic Society, spoke highly in reference to the rapidity of the process. I have great confidence in the statements .of this skilful amateur, and I am ready to admit that with a Gordon plate freshly prepared, with an extra-rapid lens, and with an exposure more or less long, it would be possible, as Count Nostitz states, to obtain a poitrait in the open air, or even in the studio, but this would be an exception; for after very numerous essays, I have fixed the exposure of plates pre pared by the simple gum process, when taking landscapes with contrast in a good light, at three times that necessary for a wet plate; and if 1 do not mistake, it has always appeared to me that the addition of gallic acid, even when supplemented by iron development, tends to render a some what increased exposure necessary. The strength of the solution of gallic acid proposed by M. Manners Gordon is 3 grains to the ounce of water.