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The photographic news
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- 7.1863
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- Bandzählung
- No. 263, September 18, 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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446 THE PHOTOGRAPHIC NEWS. [September 18, 1863. the process in detail. We then suggested that the obtaining of half-tone was probably due to the action of light reaching that portion of the sensitive compound which was in contact with the paper first, the principle being similar to that upon which M. Fargier obtained half-tone in his carbon prints. Mr. Sutton says :— The principle of getting half-tone consists in printing through the paper, because then none of the material which is acted on by light is subsequently washed off, and the intensity of black ness will depend upon the exact power of the negative to stop the light in its different parts. The paper is so thin, and its sur face so fine, that printing through it does not injure the defini tion. And lastly, the black stuff is so perfectly soluble in tur pentine, where the light has not acted, that the whole of it is dissolved from those parts, leaving them as pure and stainless as if nothing had been applied to the paper. We ascertain further from the pamphlet before us a fact which had previously escaped attention, namely, that this suggestion for the production of half-tone was not originally due to M. Fargier, but to one of our own countrymen, Mr. Blair, of Perth. M. Fargier’s process was patented in the latter part of 1860, whilst Mr. Blair’s letter, containing the suggestion, was published in the Photographic Notes, in January, 1859. As we conceive this to be a very important point in the improvement of carbon printing, we think it important to give to Mr. Blair the definite recognition of his original suggestion. We now extract Mr. Sutton’s brief resume of the history of carbon printing. Before proceeding to the history of carbon printing it is neces sary to define clearly what is included by the term, because, unless a precise definition is now given, it might be supposed to include processes of a different nature, but which lead to a some what similar result, when it is only required to obtain copies in which the dark parts consist of lines or dots. By carbon printing, in its strict sense, is meant the art of ob taining a positive photographic copy from a negative, at one operation, by the direct action of light, the carbon being mixed with the sensitive material that is applied to the paper, and then fixed to the paper by the action of light. There are other pro cesses in which an image is first obtained upon a photographic tablet by the action of light upon some chemical substance which does not contain the carbon, and the carbon is afterwards applied to the image and made to adhere to the dark parts of it; but those processes must not be confounded with that which is more strictly defined as carbon printing, and which is the only one that will at present render half-tone. To prevent confusion, the latter might be called direct carbon printing, and the former applied carbon printing. The various photolithographic pro cesses, and probably also the phototype of M. Joubert, come under the latter denomination, and no allusion need be made to them in this work, because they are based upon a different prin ciple from that which is described here, and will only yield suc cessful impressions in lines, or dots, and not in half-tone. Having thus defined carbon printing, the history of that art will evidently not include any account of the labours of those who have employed solely the applied processes, for purposes of obtaining copies of objects in lines or dots. We are simply con cerned now with the history of an art by which it has been found possible to reproduce successfully in carbon all the delicate gra dations of tone which exist in a good negative photograph. Of course the art of carbon printing includes the process of printing on the same principle in various coloured pigments, since these merely take the place of carbon in the operation. The first suggestion of the idea of employing colouring matter in a state of mixture with a sensitive substance, in order to get a coloured positive impression by exposure to light, is due to Mr. Mungo Ponton. That gentleman, in the year 1838, published in the Edinburgh New Philosophical Journal the account of a pro cess by which he prepared sensitive positive paper with a mix ture of bichromate of potass (the sensitive substance), and sul phate of indigo (the colouring matter), and thus obtained a print in which the lights and shadows exhibit different shades of green. In the above process, it will be observed that the colouring matter, sulphate of indigo, is not strictly a pigment but a coloured solution. The next step was not taken until many years afterwards. In 1855, M. Alphonse Louis Poitevin took out a patent in England, bearing date December 13th, in which he vaguely describes a process by which a direct carbon print may be obtained. The following is an extract from that part of his specification which bears upon this subject:— I apply various liquids and solid colours upon paper, cloth, glass, and other surfaces, by mixing such colours with a mixture composed of equal parts of a concentrated solution of albumen, fibrine, gum arabic, gelatine, or similar organic substance, and a concentrated solution of bichromate of potass, or of any base which does not precipitate the organic matter of the first solution, and applying this new mixture or combination to the paper, or other fabric or surface. The photographic impression is produced upon this prepared surface by the action of light passing through a negative photographic picture, or an engraving, or other suitable object, or screen, or in the camera obscura, and it is then washed with a sponge and a large quantity of water. The albumen, or other organic matter, is rendered insoluble at the parts where it has been acted on by the light, and the design is thus produced in the colour which has been employed. Mixtures containing different colours may be applied to different parts of the surface corresponding to different parts of the nega tive or screen employed to produce the photographic impression. A design in several colours may thus be produced. The proportions of the materials may be varied. What I claim as new is, the mode of printing upon paper, cloth, glass, or other suitable surfaces, by applying to them a mixture of liquid or solid colours, with the aforesaid chromatized albumen or other organic matter, and exposing to light as hereinbefore mentioned, and afterwards washing away those portions of the mixture which have not been acted upon by the light, as hereinbefore described. There can be no doubt that the above patent contains the idea of a process of direct carbon-printing; but there is no evidence to show that M. Poitevin ever produced a carbon print by tlie process described until some years afterwards, when Mr. Pouncy, of Dorchester, had done so, and given an exact formula. It is notorious that a large proportion of the patents granted in this country are for mere ideas, and there is no evidence to show that M. Poitevin's process was anything more than an idea. He never publicly exhibited a carbon print taken by himself prior to the publication of Mr. Pouncy’s exact formula, although repeatedly challenged to do so. The idea which he patented was evidently based upon Mr. Mungo Ponton’s pro cess, and is but a very slight extension of it. It is needloss, however, to say more on the subject, because M. Poitevin’s method has now been superseded by one infinitely better, and his patent was allowed to lapse. The next in the field was M. Testud de Beauregard. He took out a patent in England, bearing date December 12th, 1857, for an invention which consists in producing photographic proofs or pictures by means of carbon or other colouring matter, applied by superposition, to a coating sensitive to the action of light. The following are the particulars gathered from his specification:— Paper is immersed in or floated upon a warm solution of bichromate of potass or ammonia, mixed with gelatine. It is then dried, and its surface covered with the pigment. The pigment may be rubbed over the dry surface with a pad of leather or other suitable material, or it may be ground very fine witlr nut oil or other oil, and rubbed over the surface, which is subse quently immersed in a bath of ether, to which a little collodion may bo added; or the paper may be immersed in a bath of Indian ink, or other pigment, ground up very fine with water and mixed with gelatine, and a little gum or dextrine, and used hot; or rollers, or presses, or other appa ratus may be employed to apply the pigment or assist the operation. The paper having been prepared in the dark, is exposed to the action of light and washed in hot water. This dissolves the gelatine which has not been acted on by the light, but does not dissolve that which has been rendered insoluble by the action of light, and which insoluble gelatine retains the pigment, and thus produces the image. Glass or other substances may be substituted for paper. By employing carbon, pigment, or finely-divided gold or silver, photograplis or pictures of the greatest permanance and durability may be obtained. As in the case of M. Poitevin, there is no evidence to show that M. Beauregard ever publicly exhibited a carbon print taken by the above process prior to the publication of Mr. Pouncy’s method a few months afterwards. The history now takes us to the part which I have myself played in this matter. Without knowing anything of whatM. Poitevin or M. Beauregard had patented, I published the following leader in my Photographic Notes of January 1st, 1858 Some experiments in which we were engaged a few weeks ago, lead us to believe in the possibility of printing in carbon, by the following process : First,—Dip a sheet of blotting-paper in a mixture of bichromate of potass albumen, and finely-ground charcoal; or blacken it (in the dark), win Indian ink, ground up with a solution of bichromate and gelatine, o albumen. ‘ Next,—Dry the blackened paper, and expose it to light under a ne8Au • Lastly,—Immerse it in water, which will more or less perfectly ret _ the black material from those parts where light has nof acted with turbing those parts where light has acted, and thereby rendered it ins
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