The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
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• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

May 9,1862.] THE PHOTOGRAPHIC NEWS. 227 ), 1862. — i to unde? 1 the por once ta 1 les at a t e horroB ' >ur or sol he portn) n at last!' e operatir or the P els at ob‘ e his hed lim a sets ; the nx* approprig ers may! ted vhe grapher,/ npasses V u easel’ the law’ and a P istly, the > take 0 est inst landsc, ackgrou and the W* ch who'’ it of pill ated oo® he curtal m. ke a likt one mo"? I i with tl: I less is a I it actio"' f You ft? a frant sneeze, f 1? squintin s gettin, > it. » fore me- URE. ates pn” , thoug) ilimited osure, i" ly a fe I gth and | gatives | expen- carried itaining I :ing for I camera, I ay, and will see be sup- it mid- re been nestion arises. .By what change is the image removed, and under what circumstances is it possible to keep plates without injury for a reasonable time after exposure ? Perhaps you or some of your correspondents can give the desired information ; a any rate, the above fact may be useful to some of your readers in guarding them from one source of failure.—Yours truly, G. S. Penny. Cheltenham, May Zrd, 1862. [The specimen received is an interesting illustration of the experiment described. One half of the picture is bril liant and well detailed ; the other one universal grey, sky and foreground alike, without detail, and the barest indications of objects as seen through a dense fog. It would suggest a plate which had not received a twentieth of the proper ex posure, which had by pushing development given some traces of an image, and then become buried and veiled in general reduction, in which, however, there was no density. Dr. Hill Norris states that his plates if kept too long after exposure, before development, gradually lose the image, and in time return to their original sensitiveness. He also states that the acetic acid or its vapours will remove the latent image impressed by light. In order correctly to investigate the subject, we are brought again to the interesting but ill-understood question of the exact Operation of light in producing the latent image. Dr. Norris believes it to be what he terms an excitation, an action set up in the molecules, which, if not continued by the action of a developer, gradually subsides, and the status qu0 is restored. Apart from the question of theory, how ler, the fact described is an important one, which our readers will do well to mark.—Eo.] INTENSIFYING DRY PLATES. Sin,—-I am much obliged to you for your observat:ons on Uy communication in last week’s News. You have hit the right nail on the head. The best mode of dealing with dry plates which show a thin image is to re-develop immediately after fixing. Since I wrote to you, I found I had two plates which had not been fixed. Having cleared these and washed 'veil, I applied a 20-grain solution of nitrate of silver to the him, and proceeded to gain intensity with citro-pyrogallic ® the usual way. The result was satisfactory, no further treatment being requisite. I can also confirm what you state as to the expediency of employing a weak solution of iodine, Or of iodide of mercury. If the solution be too strong, or he kept too long on the film, the image becomes almost obliterated. This was the case with a stereo plate, one of the first I had endeavoured to strengthen ; the iodide of Mercury having entirely buried one of the pictures, and left '"t a faint trace of the other. Three days ago I took this Plate to the dark room, moistened the film, poured over it a 20-grain silver solution, and finally redeveloped with citro- Pyrogallic. The picture, of which a faint trace only was discernible, quickly came out very strongly, but the other did not reappear at all. The former was much too dense, the half tones being destroyed, and the plate rendered utterly Worthless for printing. The experiment, however, is instruc tive as to the results to be anticipated from the employment of too strong a solution of the mercurial iodide. 1’he great point to be observed in all plates which require intensifying with bichloride of mercury or solutions of iodine, is that the image to be intensified contains a suffi cient amount of silver; for if this is not the case, the result can scarcely be other than unsatisfactory. For this reason, ia evelopment with pyro and silver should invariably follow ie fixing operation; and where that course has been onii 21, it should be resorted to prior to the employment of any o er means of obtaining intensity. After this, should Feiter ' ensity be requisite, the mercurial iodide will con it fin iaresbeing taken that the solution be weak, and that poure oft the film immediately the blackening of the image has taken place. Should too strong a solution be used, and the film become converted into yellow iodide, the remedy seems to be thorough washing, then pouring a solu tion of nitrate of silver over the film, and finally redeveloping with citro-pyrogallic. After this, any iodide still remaining on the plate may be removed by hypo, without danger to the image. I regret having overlooked Mr. Hannaford's method of intensifying, given in vol. v. p. 336 of the News. Had I seen it before I determined to write to you, I should probably not have intruded on your space. On reference to the last edition of Hardwich, p. 345, I find he has detailed the pro cess of strengthening with sulphide of potassium, to which you allude. But my strong impression is that for dry plates, there is nothing preferable to citro-pyrogallic and silver for the purpose, and that the iodine and mercury solutions should only be resorted to when this method fails, as it sometimes will, to bring up the density to the required point. In the present state of dry plate photography, the subject on which I have ventured to occupy your attention is, or will be, one of great importance. If the experience of this year’s summer and autumn should prove that dry plates can be so prepared as to be as sensitive as wet, and that they may also be rendered available for all purposes of instan taneous exposure, then the best mode of strengthening them must form an indispensable chapter in future treatises on photography, and the sooner the subject is ventilated and thoroughly investigated, the better will it be for the interests of the art.—I remain, sir, yours respectfully, Amateur. [We are glad to receive from such an intelligent photo grapher as we know “ Amateur” to be, confirmation of our suggestions on this subject. He rightly observes that it is likely to become a very important one, especially if simply washed collodion plates take the position which some antici pate for them.—ED.] Dear Sir,—In reply to the letter of an “Amateur,” in which my name is mentioned, I beg to say that the solution I use for strengthening negatives, can be used for dry as well as for wet plates, if carefully applied. Instead of one minute being sufficient to produce the “ cream colour,” it would probably take from half an hour to three hours, de pending on temperature and various other circumstances. I would advise your correspondent to exercise a little more patience in conducting his experiments, he would then perhaps, succeed better, and not hastily condemn processes, which in other hands, produce the best results. In contrast to what an “ Amateur ” says, allow me to quote the following from the letter of a professional photographer, recently received. He says, referring to other processes he had tried, “ So I have come to the conclusion, after much time and trouble, that there is none so valuable for its certain results and its artistical qualities as your own; with it I can always get any amount of density or delicacy, and by any of the others I could not.” I do not claim any originality, as the process is merely a modification of one used by the late Mr. Archer.—Yours very truly. A. Brothers. Benzine.—This fluid reaches the point of ebullition at a lower temperature than turpentine, and necessarily at a much lower heat than linseed oil, which in varnish making is com bined with it. It volatilizes at a very gentle heat, and forms an explosive gas, in connection with the air, scarcely less dangerous than gunpowder. In the present instance the room was nearly air-tight, and the force of the explosion was equivalent to that of a gunpowder magazine. GxowiNG of Plants by the Electric LIGHT.—M. Herve Mangon, of Paris, France, has succeeded in growing the seeds of rye under the influence of the electric light alone. The plants assumed their green tint rapidly and vigorously, and showed no perceptible difference from those grown in ordinary daylight.