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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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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 256, July 31, 1863
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The photographic news
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Band 7.1863
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- Register Index 619
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Band 7.1863
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362 THE PHOTOGRAPHIC NEWS. [July 31,1863. other very important economic applications of the process. A transfer, with perfect half-tone, may be made to copper, stone, or zinc. It may be made an adjunct to an enamel process. It will, probably, become very extensively used in ornamentation. We see a most important position for it in photographic printing on earthenware and china, as a trans fer exactly similar to that now used in the potteries, but with photographic image, may be without difficulty pro; duced. Various other uses may also follow, which wo nee® not glance at now. , We have given a simple, unvarnished, and unexaggerated sketch of the process and its results, avoiding everything like enthusiastic epithet, feeling that, having reference to the past, we best serve our readers and Mr. Pouncy by doing so. We have, nevertheless, been very highly delighted with what we have seen and produced ; and, if all our anticipations and hopes in connection with the subject arc fulfilled, it wil prove one of the most important steps yet secured in the progress of the art. We should add, in conclusion, that Mr. Pouncy’s arrange, ments in connection with his patent appear to us to bo liberal. He is arranging to supply the prepared papei. ready for exposure, to any one at about a guinea a quire, so t m amateurs will be able to experiment without a license. T0 professional photographers, wishing to use the process io commercial purposes, he intends to supply an annual licence . To professional printers this amount wi tually clears the lights and finishes the print. It is now laid on blotting paper, a strip of which is played at the bottom edge to absorb drainings, and then dried in the sun. Care must be taken not to touch the face during the opera tions, for whilst the ink is not acted on by a solvent, it is easily smeared until it is dry. Other solvents than tur pentine might be used, but turpentine appears to answer best. It may be used over and over, merely using each time a little fresh, to remove the final traces of soluble ink and secure purity. Nothing can be more interesting than to witness the completeness with which every trace of the ink leaves the whites in the most perfect purity. With turpen tine there appears to be no danger of injuring the print, however long its action may be continued, not even a trace of half-tone being dissolved. But with a stronger solvent, such as benzole, for instance, great care is necessary, its prolonged action impoverishing the print. Where the operations are sufficiently extensive to make the cost of turpentine a consideration, it is probable that it might bo utilized for some purposes where the ink it had collected whilst in use would not be objectionable, as, for instance, in black paint. As the price of turpentine has for some time been high, costing now, we believe, about eight shillings a gallon, this might become a matter worthy of consideration. The lights of the cleansed prints, on the most satisfactory paper, are quite transparent, becoming white, of course, when mounted. A slight tint might easily be secured, in subjects needing it, by mounting on a tinted paper. Mr. Pouncy recommends varnishing the prints, first with a spirit varnish, and then with the usual varnish applied to maps, prints, &c. We are inclined to think that this will not be necessary, and will be in some instances objectionable. With the sample of paper we have referred to as most suc cessful, the print may be mounted face downwards, the print showing perfectly at either side. For some experiments ordinary tracing paper has been used, which answers very well, but not so perfectly as the sample to which we have just referred. It will be seen that, apart from the question of cost, an immense saving being effected by dispensing with silver and gold; apart from the question of permanency, the greatest question of all, there is a great saving of time in absolute manipulation. The removal of the ink is an operation about equivalent, in its demands upon time, to toning. There is then no fixing, and no interminable washing; the print is completed. As will be seen from the specification, there are various portions are varied with circumstances ; generally, as much pigment is added as will make the mixture the consistency of cream, and as much of the bichromate as will remain in the solution, which is a very small proportion, as it is very sparingly soluble in turpentine. A suitable paper is first slightly sized with gelatine, and when dry, brushed over with the preparation of printing ink, and then dried. The paper so prepared, and kept in the dark, will remain ready for use without deterioration for an indefinite period, some months certainly. This blackened paper, when placed under a negative and exposed to light, undergoes the change to which we have referred: the parts of the ink on which light acts become insoluble, whilst the protected parts remain, as at first, soluble in turpentine, benzole, &c.; and, what is singular, the amount of insolubility is in sufficient gradation to leave on the paper just the proportion of ink which shall register every variety of tone in the negative. And here is to be noted another valuable little point of detail in the manipu lations. As we have already remarked, the weak place of most carbon processess hitherto has been the difficulty of securing half-tone. This was largely overcome by M. Fargier’s modification. He rightly conceived that one source of the difficulty lay in the fact, that as the action of light commenced at the surface of the layer of gelatine, bichromate, and carbon, spread on paper, it only penetrated through the most transparent parts of the negative con stituting the deepest shades. The parts constituting the half tone were only acted upon superficially, the part in imme diate contact with the paper being unacted upon, was, there fore, readily dissolved entirely off, and the result was a print with hard black and white tones, without perfect gradation. He, therefore, coated the exposed layer of gelatine, &c., which was used on glass instead of paper, with collodion, and immersed the plate in water, which detached the film ; the unaltered gelatine, &c., was then washed away from the underneath side. By this contact with the collodion every part acted upon by light was preserved, and half-tone secured. Mr. Pouncy, possibly without having noticed the coincidence, acts upon a similar principle. He uses a fine, thin wove paper, of the quality known as bank post. This is made transparent before it is coated with printing ink, and the printing is effected through the paper. The inked side never comes into contact with the negative, but the plain side of the paper. How far half-tone would be secured if the inked side were printed on, we cannot, with certainty, say, but we have no doubt that the method of printing through the paper, and thus securing the first action on those parts in immediate contact with the paper, must materially tend to secure half-tone. For this reason, when ever the slightest action takes place, a thin film of ink in immediate contact with the paper is rendered insoluble. All but that thin layer will be subsequently dissolved and removed, but the half-tone remains. The transparent parts of the negative permit the full action of light to pene trate the entire thickness of the layer of ink, and thus the deep shadows retain a full body of insoluble ink, and are the blackest portions. On slight reflection it will be readily seen, then, how this mode of printing through the paper conduces to the production of half-tone; and this is our ex planation of the great superiority of these prints in this particular. Whether Mr. Pouncy holds the same view, or whether his practice may confirm it, we do not know, as we did not enter into theoretical considerations in our inter view. ' The proper exposure may be learned by experience, or by the exposure side by side with the negative of a trial piece of paper. Being black to begin with, examination affords no clue to the process of printing. When the expo sure is completed, the print is immersed in a dish of turpen tine, which dissolving the ink which is not acted upon, and removing it, reveals the image, consisting of the gradations of insoluble ink. After draining a few minutes, the print pu, is removed to another dish of clean turpentine, which effee- | for five guineas.
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