The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• 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-id1780948042-186800009
• PURL: http://digital.slub-dresden.de/id1780948042-18680000
• OAI: oai:de:slub-dresden:db:id-1780948042-18680000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

October 2, 1868.] THE PHOTOGRAPIIC NEWS. 477 at their work, and furnished a material, therefore, which was of such mediocre quality that photographers who had resolved to give the new product a trial were at once frightened away altogether. The paper possessed all the faults inherent to glass plates coated with collodion, such as streaking and fogging caused by the bursting of collodion bubbles, these faults giving rise to dark spots whenever the paper was printed. Besides, the collodion employed for coating was often of unequal composition, and the paper not sufficiently glazed, so that pictures were sometimes pro duced upon the collodion paper which were inferior in point of brilliancy to those furnished by good albuminized paper. At another time a whole batch of the prepared paper was sent into the market, and became unserviceable after a short time, owing to the addition, during its manu facture, of too large a quantity of resin. M. Obernetter, of Munich, who has built a factory on pur pose for the preparation of collodionized paper, experienced with his first products, made at the new manufactory, the greatest difficulties, arising, in his opinion, from the damp walls of his workshop. The paper when treshly prepared was perfectly good, but after a fortnight, or three or four weeks, a change came over the material, and rendered it quite unserviceable. For some time he was unaware of this serious evil, and every batch was tested, and being found of proper quality was at once sent off; but in a short time from every part of the world came complaints. As soon as the cause of injury was discovered, the workrooms were con tinuously heated, but without result; and it was not until the heat of the summer had perfectly dried the walls of the factory that the evil disappeared of itself. “ I have found out,” wrote M. Obernetter to us at the time, “ that the application of a preparation of gutta-percha prevented the pealing off of the film and its liability to become damaged, and at the same time increased the dura bility of the picture to such a degree that sulphuric acid or a solution of cyanide of potassium might be poured upon the prints without injuring them in any way.” All these experiences are undoubtedly of value, although it is to be deplored that they were acquired so late and at a time when many photographers had relinquished their trials of the material. A third cause of failure was due to the employment of old used-up gold and hyposulphite baths of the ordinary strength in the manipulation of the collodion paper, a course of proceeding adopted in direct opposition to the directions given by the manufacturers, who stated dis tinctly that no other solutions than those indicated by themselves should be employed ; the consequence was, that in many cases the sensitive film was found to become detached from the paper during the processes of toning and fixing. Although we have on a previous occasion already made known the instructions drawn up by M. Obernetter in regard to the employment of collodion paper, we consider it desirable to recapitulate the same with a few important addenda. Instructions to be Observed in the Use of Collodion Paper. Ihe printing is to be done in the shade, the pictures being copied to a degree but slightly more vigorous than that desired for the finished print. The toning is conducted by placing the prints first of all in ordinary water, without addition of common salt, to remove the superfluous nitrate of silver; three changes of water in a quarter of an hour will be amply sufficient. The toning bath is most conveniently made by keeping in stock two solutions, thus composed :— 1 .—Distilled water... ... ... 50 ounces Sulphocyanide of ammonium... 40 grammes Hyposulphite of soda 3 „ Bicarbonate of potash... ... 1 gramme. If the gold compound used is neutral, the last-named may be suppressed. 2 .—Distilled water 50 ounces 1 uro chloride of gold ... ... 2 grammes. By chloride of gold is meant a pure compound, free from acid and water, and not salts of gold ; if the latter is em ployed, about double the quantity should be taken, as it contains but half the amount of gold. If, after five minutes’ immersion in the gold bath, the pictures still remain red, and do not assume a beautiful violet tone, there is not sufficient gold present, and more solution must be added until the prints tone quickly ; the bath must on no account give an acid reaction. Both solutions are endowed with good keeping qualities. For use they are mixed in equal proportion, only so much being taken as is required for immediate employment. In ' this way a couple of pictures may be at once toned without delay in quite as economical a manner as a large batch ; moreover, no chance of the prints becoming yellow need be feared by using these solutions, for it is this bath, and this only, that can be relied upon for the production of faultless pictures. Other baths have a tendency to dissolve off the film of collodion. When the prints have attained the desired tone, which occurs in from two to ten minutes, they are washed in ordinary water, and fixed in a solution which should be compounded exactly in the following proportions, viz., 40 grammes of hyposulphite of soda dissolved in 32 ounces of distilled or ordinary water. The fixing will be completed in five or ten minutes, and then a subsequent washing of two to three hours will suffice to remove the weak solution of hyposulphite. In all the manipulations care must be exercised not to I bend the paper or to injure the surface with any sharp instrument, as by this means the collodion is easily torn ; no cutting or trimming should be done before printing. When the prints are laid in the first water bath, after their exit from the pressure frames, they are inclined to curl them selves up : this is of no material importance, and if they are laid, face downwards, in the toning bath, they again become straight in a few minutes. Too many prints must not be allowed in the toning or fixing bath at the same time, as red spots are thereby caused. When the pictures have been thoroughly washed, after fixing, it is as well to lay them one upon the other, face downwards, on a plate of glass or clean board, and to press them with the hand, so as to expel the water; they may afterwards be placed in an upright posi tion, so as to drain thoroughly. While the pictures are yet damp they are trimmed and mounted ; or, if it is deemed in convenient to place them at once upon cardboard, they are again heaped upon one another to prevent their becoming completely dry. In order to facilitate the trimming of the prints, it is best to mark upon the negative, either by means of a needle or a black line, the size to which the print should be cut. As a mounting material, ordinary starch paste, freshly boiled, is recommended. Rolling the finished print conduces much to its beauty, and a coating of paper varnish is advisable, inasmuch as the film is thereby protected from injury. These instructions are so clear that a close observance of them cannot fail to ensure success. Our honoured colleague, Professor August Freund, has nevertheless suggested several improvements which wc cannot withhold from our readers, especially as they are designed for producing greater dura bility, one of the principal arguments in favour of the adoption of collodionized paper in place of that prepared with albumen. “ The rolling up of the picture when placed in contact with water is only to be avoided by employing at first just sufficient water to moisten the print, and, after a few minutes, when the same has become perfectly sodden, to add a larger quantity of liquid. That the sulphocyanide of gold bath only can be used I have likewise found out, although the papers prepared by myself in Vienna some time since could be toned in any ordinary bath. The collo dionized paper at present manufactured does not give good results with any toning bath but that of sulphocyanide ; and I have likewise found it necessary, besides washing the