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The photographic news
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- 12.1868
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- Bandzählung
- No. 511, June 19, 1868
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The photographic news
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Band 12.1868
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- Titelblatt Titelblatt I
- Kapitel Preface III
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THE PHOTOGRAPHIC NEWS. Voz. XII. No. 511.—June 19,1868. CONTENTS. PIGE Mr. Gordon’s Gum Process , 289 Penalties for Piracy not Debts 290 Pictures in a Cup of Tea 290 Photographic Printing in Silver, Theoretical and Practical. By W. T. Bovey 291 Hints on Portrait Photography. By Charles E. Pearce 292 Photo-zincography in Practice. By J. Waterhouse, R.A 293 PAGE Pictorial Effect in Photography. By II. P. Robinson 295 Professor Smyth’s “Great Pyramid ” Bath. By Dr. Mann ... 296 Notes on the Carbon Process 297 Proceedings of Societies—South London Photographic Society... 297 Correspondence—Intensifying Negatives—Neutral Toning Bath —Approximate Natural Colours in Photography 299 Talk in the Studio 299 ] To Correspondents 300 MR. GORDON’S GUM PROCESS. We have recently had an opportunity of witnessing some of the exposures of some of Mr. Gordon’s gum plates, and ex amining the negatives produced. It would bo simply im possible for anything to be more technically beautiful than these negatives : they are so exquisitely delicate, clean, bril liant, and free from blemish of every kind. Mr. Gordon, who is one of the most extensive and able dry-plate experi mentalists we know, after long trial, believes this take it altogether, the most perfect dry process he has tried. In recording this verdict, we ought to add that it possesses much weight from the fact that Mr. Gordon is not only a very extensive, skilful, and conscientious experimentalist, but he is not a claimant for the honours of invention. He has no foregone conclusions to vindicate, no pet bantling of his own, the pre-eminence of which he feels bound to maintain at all hazards. This process, as many others he has worked and improved, he has found in existence in some crude form. He has worked with it, carefully modifying various features, as extensive experience and a keen perception of dry-plate necessities have suggested. This kind of modification is, in many cases, inventing a process; and although, as we have said, Mr. Gordon repudiates for himself such claims, we are compelled for distinction, as the process is distinct from others, to call it Mr. Gordon’s Gum Process. The feature which has astonished us most is the extreme sensitiveness of plates which will keep almost indefinitely. Take a recent example : a portrait was tried on a wet plate with iron development, everything working well : the expo sure was fifteen seconds. A gum dry plate was then tried under all the same conditions as the wet plate, and an expo sure of twenty seconds was given. After development, both plates were found to be fully exposed, that on the dry plate being no whit less soft and delicate than that on the wet plate. This, it will be seen, was only one-third longer than the exposure of wet collodion. Mr. Gordon states as his experience that twice the exposure of wet plates is the out side time required. The plates we examined had received various exposures, from two seconds to two minutes ; that which had received two seconds, we saw exposed on a group of cattle, and gave a capital negative. As a rule, great sen sitiveness and good keeping qualities have been regarded as incompatible; but here are plates which will keep without deterioration during many months, possessing a degree of sensitiveness very rarely found in dry plates. The keeping qualities here, however, seem perfect. Mr. Gordon recently developed a plate which had been kept a month before expo sure, and a fortnight after exposure before development. The result was perfect, no shortcoming of any kind indi cating that the plate had suffered by the length of time elapsing before exposure and before development. A recent modification which Mr. Gordon has made has I secured several advantages. Instead of using the alkaline development he originally described, he now uses the gelatino-iron developer. The use of the iron solution makes no modification in the time of exposure, but it is simpler, materially decreases blurring, rendering the use of red paint or blotting-paper at the back of the plate unneces sary, and yields a negative scarcely distinguishable from a wet plate in colour, delicacy, and all characteristics. The iron developer consists of from 20 to 30 grains of protosulphate of iron, 15 minims of glacial acetic acid, and I grain of gelatine in an ounce of water. The gelatine is dissolved in part of the water and the acetic acid, and then added to the iron salt, which is dissolved in the other por tion of the water. A trace of silver solution is added— about two drops for a cabinet plate—before commencing the development, and a little more as may be required to bring up the intensity. The negatives have small touches of bare glass on the shadows, showing that where light has not acted there is no reduction of silver. The gradations are delicate and crisp up to the highest light; excessive density or hardness being quite absent. The iron development has another special advantage : it considerably removes the one failing of gum plates—a ten dency in the film to leave the glass. This, with the alka line development, is, in unskilled hands, at times trouble some, but with the iron is almost entirely absent. Some of our correspondents have complained of the occurrence of blisters during the progress of development, a defect which Mr. Gordon had not experienced. Wo suspect that the term blister is here employed to indicate the gradual loosening of the film from the plate, which occurs at times, leaving it only attached at the edges by the line of varnish rim round. However, we submitted the letters of two or three correspondents to Mr. Gordon, that they might secure the advantage of his experience as to the defects described. Here is his answer :— “ DEAR Ma. Simpson,—I cannot account for the blisters your correspondents meet with in the gum process, unless they dry their plates artificially. “ They should always be allowed to dry spontaneously. “ An excess of nitric acid, or the use of acetic acid in the bath, is against adhesion of the film. “ I have never (as yet), I am happy to say, seen a blister on a gum plate ; the adhesion is, perhaps, worse with it than with most other preservatives, but it does not with me show this in blisters.” In answer to a question as to the length of time neces sary for the preservative solution to soak into the film, he adds,— “It is quite sufficient just to swill the film for a few seconds with the gallic acid, and then apply the gum, and this latter to be worked about the plate (say) for a minute or so. —Yours faithfully, R. M. Gordon.
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