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The photographic news
- Bandzählung
- 24.1880
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- 1880
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- Englisch
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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. 1132, May 14, 1880
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- Paginierfehler: S. XII als S. XX gezählt.
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Zeitschrift
The photographic news
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Band 24.1880
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- Register Index 631
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Band 24.1880
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May 14, 188O.| THE PHOTOGRAPHIC NEWS. 237 A Communication to the South London Photographic Society. of photographs of the famous Banqueting Hall at Haddon, but never anything to compare with a little picture of it I have just received, taken on a gelatine plate by Mr. Manfield, of Northampton. The “ Topic ” for next week will be “ So much for Employers who know nothing of the Business,” by Geo. Bradforde. THE FERROUS OXALATE DEVELOPER. BY F. YORK.* When I first commenced using gelatine plates I formed a favourable impression of the ferrous oxalato developer, from the circumstance of the results so closely resembling a bath plate ; whereas the mind had to be educated to form a correct opinion of the printing density of alkaline pyrogallic negatives. The trouble of making the ferrous oxalato and its uncertain keeping qualities induced mo to abandon it. Some time since the editors of the British Journal favoured us with a leading article on this subject, and gave a formula for mixing a saturated solution of protosulphate of iron—one part with throe parts of a similar solution ot oxalate of potash—which has worked most satisfactorily in my hands for outdoor work. Finding so few adopting it, I am induced to give tho results of my experience, and to recommend those who aro not using it to do so, as it is so simple, and does not requ’re a tithe of tho judgment neces sary for alkaline pyrogallic. This new formula (which Mr. W. B. Bolton informs us is an old eno of Mr. M. Carey Lea’s, and which ought, therefore, for distiuction, to bear his name) holds in solution tho by product, sulphate of potash. I cannot find that this is of the least consequence. I have tried the two on separate sides of a stereoscopic plate, and find that Mr. Carey Lea’s developed in one-third the time of tho recognised formula of dissolving ferrous oxalate in oxalate of potash. I have also tested different proportions of oxalate of potash, and find that with each addition tho same results are obtained ; but with prolonged development one to six takes twice as long to develop. This [is contrary to Mr. L. Warnerke's experience, who said he found it more energetic with an excess of oxalate of potash. There is one advantage in using a larger propor tion of the solution of oxalate of potash if it be repeatedly applied, as it prevents a deposit of insolublo ferrous oxalate, which settles on the negative like sand, requiring the applica tion of a camel's-hair brush to remove it. This, being the active developing ingredient, ought to bo in solution. Finding that the many samples of oxalato of potash in tho market varied in strength, I made some myself from oxalic acid and carbonate of potash, but I found no advantage in it. I used it in the proportion of one to three against the commercial kind, and with the same result. It is most important that tho solu tion of oxalate of potash should be completely saturated to got the proper results. This salt is not readily dissolved in cold water, so that in order to secure saturation an excess of crystals ought to bo put into a jug and boiling water poured upon them, stirred occasionally, and when cold decanted for use. Proto- sulphate is more soluble. It may be treated in the samo way, or cold water put upon an excess of crystals and shaken occasionally. It is very important that tho mixture of the two solutions should be perfectly bright. If, on mixing one part of iron to three parts of oxalato, there is a precipitate or turbidity, the oxalate is not good or not porfectly saturated. Uso one to four, or five or six, until tho precipitate is redissolved and tho mixture perfectly bright. This precipitate, being ferrous oxalate, is tho active developing agent. Tho proper way to mix tho ferrous oxalato developer is to add tho iron to tho oxalate, and not vice versa. Having board many complain of the additional expense of the ferrous oxalate in comparison to pyrogallic, 1 have developed twelve whole plates with four ounces of oxalato and one and a-half ounces of protosulphate, the cost of which was one halfpenny a plate. Mr. Warnerke says ho can develop dozens in tho samo solution, which, of course, would decrease tho expense. Oxalato of potash is now sold nt two shillings per pound, and 1 am told by a manufacturer that if the demand continues it will soon bo reduced to one shilling. There aro various kinds o oxalates of potash—binoxalate, quadroxalate, and the neutral, "ntchis tho article required for tho ferrous oxalato developer. I have tried the relative developing power of ferrous oxalate and pyrogallic acid, and find tho latter more energetic to the extent of one-third. The following is a rough estimation of the saturating points:— Protosulphato of iron, ono to three; oxalate of potash, one to four. To make four ounces of ferrous oxalate developer, take— Protosulphate of iron 160 grains Water 1 ounce Oxalate of potash ... 7 drachms Water 3 ounces Uorrespondence. DEVELOPMENT OF GELATINE PLATES. Dear Sir,—The thanks of those who use dry plates are due to you for calling attention to the very excellent and simple method of developing with Dr. Eder’s preparation of ferrous oxalate. Hitherto the preparation has been a difficult one, but with merely using the solution of oxalate of potash, and of the well-known protosulphate of iron, the matter is reduced to one of extreme simplicity. No operation requiring much experience is needed, as the plate, without wetting, is merely dropped in the developing solutions. No doubt a short time longer is occupied in development, but, on the other hand, it is not necessary to watch the operation closely the whole time, as the intensity is acquired very gradually, and with a remarkable absence of those puzzling phenomena which often accompany pyro- gallic development; there is certainly less inclination to fog and veiling, and none of the yellowness often found previously. It is no small advantage that the colour of the resulting negatives is closely similar to that of collodion, and its printing value can therefore be at once estimated accurately. It must be remembered that as no allowance is to be made for greenish yellow or other non-actinic colour of film, the development should be carried sufficiently far to give a powerful imago such as we have been accustomed to in wot collodion. If this is not done it may look thin and grey. Even then, fortunately, such negatives lend themselves remarkably well to the capital method of intensi fying indicated by Mr. England, and more than once approved in your columns. It is simply— Chloride of ammonia ... ... 1 ounce Bichloride of mercury ... ... 1 „ Hot water 20 ounces Weak negatives may be immersed after drying (preferably) in one ounce of this and ten ounces of water, and allowed to gradually intensify. Wash and immerse in water con taining a sufficient quantity of ammonia to just give an odour. All this reads rather difficult, but is, in fact, simple, and may, I think, be fairly stated to be the latest we know on dry plate practical working. Some may say that ever lasting changes are going on, and you never know where you are ; but a little consideration will show that we aro all learners, and that the method above indicated forms an exceedingly simple and effective procedure. Here let me disown any pretence of having invented any thing I have written about, or discovered it first, or any thing of the kind. There is ono caution I should like to give before ending: the ferrous oxalate system requires more careful timing than the pyrogallic. With the latter you can with ease add bromide to over-exposed plates, and keep them from running away into those wretched thin yellow flat “ unpresentable ’’ wo see so many of. I fully agree with you that ferrous oxalate should supersede pyro gallic, and also that the Continental measures of grammes, &c., should be used in place of our most difficult and uncertain system.—Faithfully yours, Samvel Fry. PAYMENT OF ASSISTANTS. Sir,—I did not mean to say another word on this subject, but since “ An Operator of Six Years’ Standing ” returns to
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