The photographic news

• Bandzählung: 29.1885
• Erscheinungsdatum: 1885
• 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-id1780948042-188500006
• PURL: http://digital.slub-dresden.de/id1780948042-18850000
• OAI: oai:de:slub-dresden:db:id-1780948042-18850000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Bemerkung: Seite I-II fehlen in der Vorlage. Paginierfehler: Seite 160 als Seite 144 gezählt.
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

fuLY 3, 1885.J THE PHOTOGRAPHIC NEWS. partly because the original support is not required to do duty beyond the point at which the development com mences. Neither of these conditions exist in the present case. Gelatine bromide papers used for developing purposes cannot be taken as a guide, since they are not so heavily charged with a gelatine emulsion as those intended for direct prints to equal, if not rival, the best productions on albumen. With regard to texture, it is not necessary to say much here, as opinions are diverse on this subject; but we pre fer to employ a fine one, for small work at all events, so as to keep the resemblance to ordinary silver printing, and for that reason take plain photographic papers, Saxe, Rive, or Renat Rive, either being well suited to the purpose. Certain English papers may be used ; those having a close texture, and well-sized, should be selected ; but they are apt to develop black spots freely after the paper has been kept a few days, especially in a damp atmosphere. This effect is very noticeable when rolls of plain wall paper have been used ; showing that, however well it may answer for developed images, or the carbon process, it is certainly not expedient to employ it in the present in stance. The degraded quality of the white, together with the probable trace of the hypo therein, renders the suita bility of English papers very doubtful. Several methods of coating paper have been described in the pages of the News and Year-Books. Among them we may mention the plan described in a series of articles relating to paper positives by the gelatino-bromide pro cess, pages 738-9, vol. xxvii., wherein the paper to be coated received a somewhat brief soaking in a vessel of cold water, after which it was transferred to a levelled glass slab edged with a light frame, and a measured quantity of the sensi tivemixture poured thereon. We have found this plan to answer. Again, on page 77 of the same volume, in the second of a series of articles on “ Silver Printing,” there is a detailed description of coating paper with albumen. This plan answers equally well for covering paper- surfaces with liquefied emulsion, but it is advisable to lower the temperature of the coating room beyond that required for albumen, and some provision is necessary for keeping the sensitive mixture in a liquid state. Perhaps the simplest method on a large scale is that which is used in the manufacture of carbon tissue, illustrated on page 453 in the last volume of the News, and which does not necessi tate damping the paper first. Such an arrangement is not available for the coating of small pieces, since it will only work in long continuous bands. For experiments it is merely necessary to mount a roll of paper with its smooth side outermost in contact with the surface of the liquid, be it either pigmented gelatine or an emulsion, the free end of the roll being then steadily and deliberately drawn up wards until the whole length has thereby become covered. Obviously an operation of this kind can be performed more satisfactorily by those skilled in the manufacture of the commercial article, and when emulsion papers for printing out become generally used, the facility for ob taining a perfectly-coated surface will doubtless be as great as it now is in the case of albumen, carbon tissue, transfer paper, bromide paper, &c.; and as such papers can be made to keep almost as well as ready-sensitized albumen paper, the probabilities point to their manufac ture on a large scale. A plan which may commend itself to the experi mentalist may be here mentioned. The rough sketch represents the model of a simple contrivance (designed by ourselves for the purpose) consisting of a board or stand S, with an upright upon which rocks a forked lever, 0. One end of lever carries a small sliding weight of lead, W, pro vided with a screw to secure it at the proper distance from fulcrum at C. The points of the fork are drilled to take a wire which passes through the centre of a wooden roller, P, upon which the paper is coiled ; one end of paper is gummed to the roller, the other fastened in practice between two slips of wood, by means of two or three brass screws or nuts, or bv springs at each end, the inner surfaces of wood being roughed. To these slips of wood is attached a cord long enough to go to the ceiling of room, to pass through an eye or staple fixed there, and to hang just within reach of the upraised hand. Two little uprights on stand UI and U2 form a place in which to rest an ordinary deep white earthenware photographic bath, as a suitable angle to form a V trough which can receive the emulsion. In practice, the fork of the lever is better made of wood, shaped like the wire of the model. To coat strips, say, one-third the narrowest width of a sheet of Rive or Saxe, the paper is cut, and the ends joined with stout gum ; the number of strips depend on height of room or position of stand, on floor or table. Care is taken that the roller is the same width as paper, and the laps in the latter are so made that each strip, beginning at the inner one, is under the next outer one, thereby presenting no edge of paper to cut against the surface of the emulsion, and so form waves ; the right side of paper must of course be outside. The bath, having been warmed, is put into its place, the emul sion poured in, and the lever, with paper-covered roller tilted on to the surface, being previously so balanced as to rest lightly thereon. One hand takes hold of the string, while the other touches the fork and keeps it from rising by the tension of the cord ; the cord is then slowly pulled until the whole of the paper has passed over the emulsion, when the roller is allowed to rise out of trough, and the bath is removed. The difficulty suggests itself of not being able to reach far enough up and down to pull the whole of the paper out of the trough when the strip is very long ; this is got over either by having a nail or roller in the edge of the table, round which the cord is passed as it reaches it, to be then pulled up instead of down ; or better still, by pro viding a little bobbin about two inches in diameter and three long, mounted in a stand, or secured to the edge of the table, and capable of being turned by a little wire handle at one end. The cord is fastened to this, and by winding, it is gradually, and very evenly, pulled through the staple above, and so the coating is steadily continuous. It is difficult, without an outer bath of hot water, to keep the emulsion liquid long enough for several rollers to be attached ; but if this is provided, there is no reason why, with two or three bobbins and rollers with cords ready attached, all could not be quickly and perfectly coated, the stand being slipped along the table to suit the position of the next staple and bobbin. The staples should be a foot or - two to the left of a perpendicular, drawn from roller to ceiling, and so slanted to avoid dust. It is all-important that an even temperature should be maintained in the coating trough when there is much used ; and it is a matter of some consequence that the maximum should not exceed 36° C. at any time. A lower tempera ture would be even better so far as preserving the white ness of the emulsion is concerned. Hot gelatine solutions, too, are difficult to spread uniformly on paper, owing to the tendency of the liquid surfaces overlapping the more exposed ones that have become partially set, and so pro ducing a series of ridges, streaks, and inequalities. These reasons alone are sufficient to indicate why an emulsion