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The photographic news
- Bandzählung
- 35.1891
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- 1891
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1702, April 17, 1891
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The photographic news
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Whatever may be the value for the abstract science of M. Lippmann’s researches, every sensible man will respect his noble endeavours in that direction, but it would be a great pity if thousands of professional investigators should lose their time and means on photographic experiments based upon un faux point de depart. L. NIEVSKY. 5, Gransden Road (Rylett Rood), Shepherd's Bush, April 1 Uh. Droceedngs of Socetes. PHOTOGRAPMIC Society of GREAT Britain. At the meeting of this Society held on the 14th inst., the chair was taken in the first instance by Mr. J. GLAISHER, the presi dent. After the reading of Mr. Willis’s paper the president left, and his place was filled by Mr. J. Spiller, vice-president. The Chairman gave out that the council had appointed a committee to deal with questions relating to the exhibition, and to act as hanging committee. The members appointed were Messrs. Baggalley, Chapman Jones, Davison, J. Spiller, and Mackie. A paper on “ Platinotype," illustrated by esamples and demonstration, was read by Mr. W. Willis. He said that the only new point that he had to introduce was the application of platinum printing to photographing on wood, but there were several observations relating to development to which he would invite attention. The first processes described were those introduced in 1872, 1873, and 1878. In the former process, there was at one stage about equal weights of platinum and silver in the print, but the silver was toned by gold and sul- phoeyanide, and the finished print contained all three metals. He had not found it practicable to carry the substitution of gold for silver to completion without producing a cold blue tone. In the 1878 process the image was formed of platinum only. In the cold bath process of 1888 the paper was prepared with ferric oxalate or tartrate, and the image developed in a bath which, in addition to platinum, contained a substance capable of acting as a developer. If, adopting the method of Herschel, a solution of silver or gold were applied to the iron-sensitised paper after exposure, an image in either metal would be obtained, but this was not the case with platinum unless some other salt was present to act as developer. There was a pecu liarity in the appearance of the image whilst developing in the mixed platinum developing solution. The image at first appeared flat and weak ; but the most noticeable characteristic at this stage was that it was granulated ; the granulation dis appeared as development went on. The difficulty with the cold bath process was to produce a perfect paper equal and regular in quality. The producing of a platinum image on wood was next described and shown. The specimens had been polished, and the wood prints were of considerable depth and richness. He had long experimented in photographing on wood, but had only thoroughly succeeded with the cold bath process. With the hot process he had found it almost impos sible to get enough platinum in the image. With the cold process, where the platinum was applied after exposure, this difficulty did not occur. He did not use hydrochloric acid when working on wood, but oxalic or citric acid of a strength of 2} per cent, instead. Panels of white wood, of which he had found chestnut to be the best, covered with photographs of decorative subjects, were, he thought, of use. In the hot bath process variations of temperature and of strength of the developing solution produced different results. As the image, before development, consisted of a soluble salt, it was desirable to develop in such a way as to obtain the result before much of this ferrous salt was dissolved in the bath. In short, the problem was to accelerate development, but not to accelerate solution of the ferrous salt. To show the effects of differences of temperature and strength of solutions, strips of paper, equally exposed and differently treated in regard to tempera ture and strength, were handed round. On the whole, a low temperature rather shortened the range. Further modifications could be obtained by various additions, of which hydrochloric acid and chloride of potassium were mentioned. Mr. J. Spiller recalled the interest which he had felt at the first demonstration of platinum printing before the Society in 1878. He would like to know whether Mr. Willis now preferred that method, or the cold bath process more recently introduced. Mr. W. E. Debenham pointed out the great range of grada tion in the specimens of the 1873 process, containing platinum, silver, and gold, and enquired whether Mr. Willis attributed that to the gloss which appeared on those prints, or to superior rendering of gradation by the process itself. Mr. Chapman Jones said that with the cold bath process the strength of the developing bath changed with each print put into it. This he considered to be a great drawback. Mr. J. Gale enquired whether the cold bath process was suitable for rough paper. Mr. G. Davison said that the question raised by Mr. Debenham was of great importance, if it was a fact that greater truth of gradation was obtainable by one process than by another ; but to make proper comparison, prints should be made from the same negative. Mr. Willis, in replying, said that he really could not say whether he preferred the hot or the cold bath process. He thought, however, that when the paper for the cold process could be perfectly prepared, that process would be by far the best. As to Mr. Debenham’s question, gradation was entirely under control. The negatives of the time at which platinum silver-gold process prints had been made were of a much more vigorous character than those of the present day. He thought the gloss on the prints might have something to do with the gradation. That gloss was entirely due to starch, three coatings of which—with drying between each coating—had been applied to the paper. In reply to Mr. Chapman Jones, there was no difficulty in keeping up the strength of the developing bath by the addition of a certain quantity of fresh solution for each small number of prints placed in the developer. A specimen of M. Lippmann’s so-called photography in colours was then submitted for inspection. It had been brought to this country by Dr. Lindsay Johnson. The Chairman, Mr. Shlleb, looked upon it rather as an iridescent film than a true specimen of photography of the spectrum. There was a red place which might be assumed to correspond to the red end of the spectrum, and a green place ; but no other colours were visible. Mr. T. Bolas thought they could hardly assume, unless it were so stated, that the red on the plate corresponded to the red of the spectrum, and the green to the green. Capt. Abney had been understood to say that each colour required an ex posure of a certain time to render itself on the plate, and that a shorter or longer exposure would produce another colour, in which case any colour might serve for producing the whole series. This particular photograph was nothing like so good a rendering of the spectrum as the one on albumen paper recently shown by Mr. Warnerke. Probably it was known to most present that Becquerel had obtained results much more suggestive of the spectrum than the one now before them. Most photographers had obtained an iridescent appearance on the edges of plates and on waste plates that was more like the spectrum than this. He appreciated M. Lippmann’s services to chemistry—he was a man of science ; but it did not appear to him that he had advanced the solution of the question of photography in colours. Mr. Chapman Jones noted that M. Lippmann had succeeded in fixing his image, which Becquerel had not done. This, he thought, was the chief point in M. Lippmann’s work. Mr. L. Warnerke believed that Poitevin had succeeded in fixing the image. He then exhibited the photograph referred to by Mr. Bolas, which he thought had nothing in common with M. Lippmann’s. As the red and deep orange had shown no action in the time (half an hour) which sufficed for the other colours, these two had been exposed for two days. The differences of colour in his examples were not due to mere amount of chemical action, for when he had exposed under a sensitometer screen, the image was of a brown colour throughout. He had not succeeded in fixing these images. Mr. W. H. Harrison said that probably the first Daguerreo type was no better than the feeble specimen of M. Lippmann’s
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