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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 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. 227, January 9, 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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18 THE PHOTOGRAPHIC NEWS. [JANUARY 9, 1SG3. author who has attempted its direct analysis, and from which, finally, we have only been able to deduce general averages, the summary of a great number of experiments. This, however, is easily understood, when we know that these varieties of pyroxyline are constantly mixed in the specimens obtained, no matter what the method of fabrica tion has been; it is therefore only the dominant species which constitute the properties, more or less characteristic, of the whole. But these species do not really exist, and why we admit them, as we have before stated, is, the varied and in determined proportions according to which is produced the absorption of the gas in the capillary interstices of the fibres of the ligneous matter.—Bulletin Belc/e de la Photographie, Upon the preceding the editor of La Lumiere, M. Gaudin, remarks:—“ I readily admit, with M. Testelin, that nitrated cotton is not constantly in definite proportion. The action of nitric acid upon the cotton differs constantly with the propor tion of water it contains, to such a degree, that in the preparation ofa single tuft, we maybe certain that the proportion first im bibed differs in nature from the portion last imbibed, in consequence of the accumulation of water in the acid, which has already acted, remaining, for I have proved, by a decisive experiment, that the reaction is instantaneous. It is also certain that the nitrated cotton is unstable by nature; with time it undergoes a kind of fermentation, which sometimes causes it to explode, and it is this which forms an insur mountable obstacle to its employment as a substitute for gunpowder. Witness the catastrophe at Bouchet, where some thousand kilogrammes exploded spontaneously, scat tering the building in which it was contained to dust, and even hollowing the earth beneath it, like a funnel. Photo graphic cotton is less explosive, nevertheless from time to time it causes serious accidents ; and quite recently, the ex plosion of some kilogrammes demolished the laboratory of M. Mathieu Plessis. “ But to conclude that the instability of the product is due to the absence of combination, appears to be an error, when we consider the known properties of photographic cotton, it dissolves, in fact, in alcoholic ether. I underline the word, to express that it is a true solution rather than a simple sus pension. In fact, photographic collodion constitutes a per fectly transparent liquid—a quality which never attaches to a body held in suspension, if held, as supposed. Upon slowly evaporating it on an impervious surface, it detaches itself in limpid glassy pellicles, which also preclude the presence of any detached body. Finally, the filtering of collodion through paper, which succeeds very well, abundantly proves that the cells, if cells there be, cannot exceed the hundreth part of a millimetre in diameter, and this absolutely excludes any idea of ligneous fibre. Soluble photographic cotton, therefore, constitutes a true combination of lignine with cer tain oxygenised products of nitrogen; but there exists also a series of these products which differ from each other by in sensible degrees, from whence results the difficulty of con stantly obtaining the same product, when following, as nearly as possible, the same conditions of fabrication.” TO SECURE CLOUDS IN LANDSCAPES. BY W. H. WARNER. In the News of this week, I read, under the above heading, a (to me) somewhat complicated arrangement for the se curing of the very beautiful effects of cloudland. Having, in the course of my professional engagements, been often compelled to resort to various “ dodges ” to effect the best results in the securing of such effects, and knowing that simplicity in apparatus is at all times desirable, I will proceed to give you my little contrivance, which was arrived at by a puff of wind having one day blown over my camera. The lens I was working with, was Dallmeyer’s No. 1 triplet, to which was attached his flap shutter, made, as you know in mahogany. My view consisted of a very white parsonage-house, with a lawn in front cut up into beds, containing a large quantity of green leaves of various shades; behind the house were some very picturesque clouds, which I was desirous of ob taining. The size of the picture was 10 by 6. Having focussed, I proceeded, as usual, to prepare the plate, when a sudden squall arose, and the catastrophe oc curred as mentioned above, whereby the flap and sides of the shutter were broken. Then the following idea suggested itself, which has since been perfected by Mr. Robert Murray of Murray and Heath, viz., to make one side of the shutter a little broader than the other, and in the place of wood to have metal sides and flap ; then to ascertain the exact angle at which the lower line of the shade divides the whiter portion of the picture from the darker, marking this by a lead pencil line on the broad side of the shutter. On ex posure, proceed thus :—open the flap at first 1-1Gth of an inch within that line, holding the brass knob by which the flap is raised in your hand, according to the exposure you wish to give the foreground ; at the same time move the shutter upwards and downwards, in a rapid movement, four or five times during the exposure of the foreground, say half an inch above the line marked on the side of the shatter in order to soften the light into the dark, and thus avoid an abrupt line ; then for a moment close the shutter; next open the whole for one or two seconds, as the case may be, to give the clouds. The same principle may be applied to the taking of street views, where you require an absence of people and perfect delineation of buildings. Having lately—in fact, at the begin ning of last month—been requested to take a view of the Ross Corn Exchange, for- the purpose of engraving, and its situa tion being in the main street, with people constantly passing and repassing, I found that to get a satisfactory picture it would be necessary, in the foggy frosty weather we then had, to give an exposure of two or three minutes. This, you see by the specimen sent, was done, the only figure being the one placed there in order to give the comparative height of the building. All this has taken much time to explain, the actual operation taking only a few seconds to effect. • THE URANIUM DEVELOPER. Mr. J. R. Woon, writing to the American Journal of Photo graphy, says :—“ I saw it stated in the Photooraphio News that Dr. V an Monckhoven was experimenting on developers, and that he had found protosulphate of uranium to develop collodion pictures with less exposure than protosulphate of iron. Wishing to try that salt for that purpose, and having some of the sesquinitrate of uranium by me, 1 converted it into the protosulphate by the following simple means ; If a solution of sesquinitrate of uranium in water - be heated with clean iron filings, decomposition soon takes place, precipitating the protoxide of uranium, which mostly adheres firmly to the excess of iron filings. If these be washed and then mixed with a warm dilute solution of sulphuric acid, the precipitated uranium rapidly dissolves, forming a dark green solution, which requires filtering. This solution, mixed with an excess of sulphuric acid, I have used as a developer, and believe it to require less ex posure than the sulphate of iron with acetic acid. Perhaps some of your readers might try it, and report.” To Put a Paper Positive into a Looking Glass.—A correspondent sends us the following, which may interest some of our readers. Having cut out the picture, take a quarter plate glass, well cleaned, lay a sheet of tin foil on two or three thicknesses of cloth or paper, and spread some quicksilver with a piece of cotton wool. Next, attach the portrait with varnish, to the glass. All being ready, lay a 'sheet of clean paper on the top of the quicksilver, and place the glass, with portrait attached, on the sheet of paper. Now press hard, and draw out the sheet of paper gently. The quicksilver will run round the edge of the portrait, making a beautiful looking- glass, with a portrait in the centre, giving an effect, something like a daguerreotype.
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