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The photographic news
- Bandzählung
- 7.1863
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- 1863
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 228, January 16, 1863
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The photographic news
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- Register Index 619
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34 THE PHOTOGRAPHIC NEWS. [January 16, 1863. sulphite of soda. This was considered an important step in the securing of permanency, and it is believed that photographs, produced with an intelli gent regard to known laws, and preserved with a care due to works of art, may be considered as permanent. Although it is an undoubted fact that the phenomenon connected with the printing, toning, and fixing of photo graphs, so as to secure under all conditions entire permanency, still pre sents more points for anxious examination and inquiry to the scientific pho tographer, yet the fact that there are in existence many photographic prints which have remained unchanged for upwards of twenty years, proves, beyond all doubt, that the causes of fading are not inherent, but accidental, and that they only require to be better understood to be entirely removed. The desire for absolute certainty as to the permanency of prints from photographic negatives has led to many attempts to substitute other sub stances for the salts of silver usually employed. In the year 1856 a French nobleman, the Duc de Luynes, in order to give an impetus and a definite purpose to efforts in this direction, offered a prize of 2000 francs for the most perfect process of printing in carbon, two years being allowed for competitors to complete their researches in. It was agreed that carbon being of all substances known to the chemist one of the most stable and unaltered, it was manifest that if it could be used for producing the blacks of the photographic design, the same guarantees would then be obtained for the permanency of photographs which exists for the stability of printed books and engravings, and that such a consummation was all that could be hoped or desired. Several competitors responded to the appeal thus made, and a commission of gentlemen was formed in the year 1858 to report upon the processes submitted by the respective claimants for this prize. •The report was made in the year 1859, in which it was stated that no process submitted at that time was sufficiently perfect to merit the entire award. The nobleman who had instituted the competition then intimated - his willingness to allow the offer to stand over for three years more, at the same time allowing the commission to divide the 2000 francs amongst the various gentlemen who had best contributed to the end in view—the’ production of permanent prints. Two gold medals, each of the value of 600 francs, and two silver medals, each of the value of 400 francs, were then awarded. A gold medal was given to M. Poitevin, as the originator of the first idea upon which carbon processes were based, viz., the peculiar action of light upon a combination of salts of chromium and organic matter. A gold medal was awarded to Messrs. Divanne and Girard for their investigations into the causes of instability in silver prints. A silver medal was awarded to Messrs. Garnier and Salmon, for a process of printing in carbon. The other silver medal to Mr. Pouncey, an Englishman, for a similar process. The commission appointed to decide upon the second competition have recently made their report, and have awarded to M. Poitevin the prize of 2000 francs, and an additional medal, value 600 francs, to M. Fargier for his process. Specimens of each of these artists’ works are in the Exhibition. Notwitstanding the fact that great progress has been made, much still remains to be desired, and a further prize is again offered by the Duc de Luynes, to be awarded in 1864, and it is still open to competition. In referring to this interesting portion of the history of the art, and accord ing high honour to the nobleman by whom it was initiated, there remain one or two remarks to be made. It would be manifestly beside the purpose of this report to enter into an examination of the claims for priority of invention made by various experi mentalists ; but it is impossible to refer to the matter without drawing attention to the fact that the germ of all these processes was the discovery of an Englishman. In May, 1839, Mr. Mongo Ponton communicated to the Royal Scottish Academy of Arts his discovery of the action of light upon paper, prepared with a solution of bichromate of potash, a discovery upon which the carbon processes and the majority of the photo-engraving and photo-lithographic processes have been based. (To be continued.') Correspondente. FOREIGN SCIENCE. [FKOM ovb special correspondent. 1 Paris, 14th January, 1863. A process for obtaining paper positives and negatives, with nitrate of silver alone, is announced by M. Gaume, of Mans. He employs a nitrate solution of the strength of 4 or 5 per cent., upon which the paper is floated 4 or 5 minutes, then dried in a dark place. The exposure in the camera must be about 20 or 30 seconds for negatives, and several minutes for positives. Both negatives and positives are developed with gallic or pyrogallic acid, without the addition of silver. They are toned with chloride of gold, and fixed in rain water. The same results may be obtained upon albumenized paper, without iodide or chloride, and the proofs are remarkable for their delicacy. By this process, therefore, pictures are obtained with nitrate of silver only. M. Regnault considers that it will be more prudent to fix with ammonia, as recommended by M. Humbert de Molard. Mr. Maxwell Lyte has pointed out a cause of fading in paper positives which has not hitherto been noticed, viz. : —the presence of sulphur in the Bristol boards, &c., used as mounts. In paper manufacture, the pulp is bleached by the action of chlorine, and to remove all traces of this bleaching agent, manufacturer's frequently put into the vat, ■ under the name of anti-chlor., a certain quantity of hyposulphite of soda. But this substance acts only on condition of being decomposed by the chlorine, and the products of the decomposition of the hyposulphite of soda, eminently unstable, always cause the liberation of a certain quantity of sulphur, which remains in the pulp, sometimes in so considerable a quantity that it is literally possible to extract the sulphur by sublimation. Besides the sulphur, there is always a slight excess of hyposul phite of soda, and it need cause no surprise when we see proofs mounted upon certain kinds of cardboard, show the fatal yellow stain, while other proofs, prepared under exactly similar conditions, remain intact if not mounted. Therefore, in mounting proofs we encounter numerous causes of fading, either from the presence of free sulphur, or of an excess of hyposulphite of soda, or of chlorine, or of hypochlorite of lime, or even from the chloride of sodium, resulting from the decomposition of the hyposulphite of soda by chlorine. We may easily detect the presence of hyposulphite of soda, chlorine, and the chlorides, by the following expe riment :— Beat up a piece of the suspected card-board in a porce lain or glass mortar with distilled water ; to one portion of the filtered liquid add a crystal of nitrate of silver, which in the course of a few minutes, gives, when sheltered from the action of light, a yellow, or even a black, precipitate, if any traces of hyposulphite of soda be present. In the ’ other portion of the liquid, previously acidulated with a little nitric acid, and boiled, also put a crystal of nitrate of silver, which, if chlorine or chlorides be present, gives a white precipitate of chloride of silver. The detection of free sulphur, rather more difficult, is made by attacking the paste of the cardboard with aqM regia entirely free from sulphuric acid, after the evaporation of the greater part of the liquid, and the incomplete satur ation of the excess of acid by a little ammonia. Then add some distilled water, and filter; the presence of sulphuric acid in the clear diluted liquid, is recognised by chloride of barium. A successful mode of treating the ashes arising from the I burning of photographic paper clippings, &c., consists in the following :—the papers are first burned in a laboratory furnace; the ashes, left undisturbed for several hours, gradually consume all the carbon ; they arc then collected together, weighed, and melted without any other treatment. After some comparative experiments made upon 150 grains of ashes, the following proportions have been adopted:— Ashes 10 parts. Carbonate of soda (dried) ... 5 „ Pure silica sand ... ... ... 2 „ The addition of the silica appears indispensably necessary. We thus obtain a very fluid nitreous slag, with a compara tively low temperature. The grains of silver are easily col lected together, and the very compact matter thus obtained dissolves perfectly in nitric acid diluted with its own volume of water. The gold mingled with the silver remains in the capsule in the form of a black powder. Generally the ashes of the refuse papers of the operating room arising from filtering papers, clippings, &c., yield from forty to fifty per cent, of their weight of silver. M. Gaudin, the editor of La Lumiere, has published his Photographic Programme for the current year, in which he points out the subjects deserving the especial attention of photographers, and to the investigation of which he intends devoting himself. First in importance stands a sensiti^ dry collodion. The defect in this is due entirely to the cohesion the collodion acquires in drying, which transform 8 it into a horny substance of a greasy nature, which does not : permit aqueous liquids to penetrate it to react upon the im pressed iodide of silver it contains. Collodion which ha 8 never ceased to be wet, may be regarded as forming spongy I film composed of extremely fine fibres interlaced, and acting J as a support to the iodide of silver. This is, at least, what
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