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The photographic news
- Bandzählung
- 6.1862
- Erscheinungsdatum
- 1862
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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. 203, Juny 25, 1862
- Digitalisat
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Zeitschrift
The photographic news
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Band 6.1862
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- Register Index 619
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Band 6.1862
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1862. ' erimenb5 . to lest ian and THE PHOTOGRAPHIC NEWS. rac6 rel’a the eal N” 2g, t 2 mr6, i the a wle te in eo iuusta , trodle malofa e intz, cg e linS^ infor®"" but •kdert ity, “W than.p iilar"" advise E 1 fromi Jlyallo^ leaves" isture, 21 faint pril2 little mo" thePsoT)- stoCorT ternatioP small ne with cOPl, tion of * enham. ; chobst^ . tobev I tils of !0 j strengt48 atterope I the uS prevent r the Pl silver,". youre02 sped? n migb"" ppere" hstt [MW'S rethans odginie I les he ropossdl I ,0z lot see t tholom’, , morphs Ip him "L The 2 ? epiti2 xampleset in curry ‘ 2 Vol. VI. No. 203.—July 25, 1862. MODIFICATIONS IN THE TANNIN PROCESS. The universal testimony to the excellence of the tannin process for dry plates, both in this country, on the Conti- nent, and in the United States, seems to promise that if it be not in its original form the dry process which is required, at least some modification of it will be. We question J’l’etlier, since its discovery, any other dry process has been half as much practised, or with half as much success. We glean from time to time additional evidence as to the tro modifications which have been recently brought promi- Dently under public attention, the hot development, and the addition of honey or a similar substance to the tannin potion. Regarding both, the balance of evidence seems to win their favour. Major Russell, the originator of the pro- 0888, in a recent letter to us, says:— “More than a year ago, however, I found out that tannin Nates, unlike most other dry plates from which nitrate has wen entirely removed, may be too dry; and in that case are 588 sensitive, less intense, and appear to solarize more readily. From this, I thought it probable that some substance which ’stained a moisture, might be advantageously mixed with the lannin, but tried no experiments in this direction, until I hoard of Mr. England’s use of honey, which I should think likely to Answer well, if not used in sufficient quantity to render the Burface sticky. I fancy, however, from theoretical considera- tions, that the same object may be obtained with still greater Bensitiveness by other means, and several weeks ago prepared a number of plates to test the matter, but have not yet exposed Ihem, on account of the unfavourable condition of the light, for I is quite useless to try experiments for sensitiveness in any ht an uniform light; and this cannot be depended on, except "hen the sky is quite bright.” Lieut.-Col. Stuart Wortley, who has just returned from taly, showed us the other day some very excellent pictures from tannin plates. He states, that he has found a similar advantage, as to sensitiveness, to that claimed for the addition of honey, when gum arabic has been added to the tannin Bolution. Some time ago the Rev. J Galloway Cowan related Smilar experience. It is only right to add, however, that we have heard in instances that these additions tended to destroy the Japing qualities of the plates. Mr. Hurst, an enthusiastic lorkshire amateur, recently called upon and showed us 80me exceedingly fine tannin negatives. He stated that on he whole he preferred the original process to any of the "odifications ; as he was willing to give the long exposure, in obtained very perfect results. He had tried the honey nd tannin with very satisfactory results. When the plates "ere freshly prepared they were decidedly considerably more sensitive than those with tannin alone. When they AA been kept a few weeks however, this advantage was lost. 4 the end of a fortnight he found them no more sensitive Pan plain tannin plates, and he had a conviction that with songer keeping they would become even less so, as the film esomed to him to become, in the course of time, contrary to all Pectations, even more completely hard than tannin alone. e fact, observed by all who have tried it, that honey and unm give a bard dry film instead of a slightly sticky one, whiomewhat unexpected ’ but that they should give a film Beem cVentually becomes harder even than tannin alone, does yerY singular, and deserves further examination, as and tannine question of the keeping properties of honey of-levalu ° of heat in developing, although still the subject cting testimony, is obtaining increased recognition. Major Russell informs us that he has been experimenting in its use. He says— “ With regard to the use of heat in the development, my brother, Mr. Branfill, used it successfully; and I tried many experiments in that way long before hearing of Dr. Draper’s experience. My experiments were not carried far enough to enable mo to speak with much confidence, but the results were very promising, as I have succeeded by the aid of heat in bringing out a tolerably good picture after about th of the ex posure which would otherwise have been necessary. There are some difficulties in working in this way, which might probably be overcome ; the picture is something like that brought out in the wet process by iron, and intensifies with difficulty. One circumstance, which I have not seen noticed is, that the image brought out by the aid of heat after very short exposure is quite superficial, and when dry can be entirely wiped off with the finger : this is probably the effect of the want of penetration of the light into the yellow iodide. After varnishing, however, the image would doubtless be firm enough to print from. Hot water is very apt to loosen tho film, if on bare glass or on gela tine ; but on a thin coating of india-rubber boars a boiling hot liquid with even less risk of moving than when a cold one is applied. I cannot as yet give any directions as to how tho hot development should bo managed ; but it will probably bo found that tho heat should bo proportioned to tho length of the expo sure, as the application of boiling water to a plate exposed about one quarter tho usual time, will start tho detail, but at the same time spoil the picture by fogging. The least trace of acid in tho water destroys tho invisible image. Pyrogallic solution is easily decomposed by heat, so it is better, if possible, to work with hot water, alternated with cool developer.” The thin feeble image, to which Major Russell here alludes as the frequent result of hot development, we have met with in our own experiments. The image is full of detail, but with no contrast, resembling in appearance tho images pro duced by an over bromized collodion. The suggestion as to the relation between the amount of heat and the time of exposure, has, as Major Russell conjectures it would be, been found of the greatest importance. Some time ago Lieut.- Col. Stuart Wortley, in a communication which appeared in the News, pointed this out; and in a recent conversation he insisted strongly on the necessity of recognising this principle. The specimens he showed us of the results of hot development were exceedingly soft and full of detail. Photographers on the Continent have recently been giving much attention to the tannin process, and Mr. Adolphe Martin, and M. Gaudin, endorse the value of hot develop ment. We may mention that Mr. Sutton, who for some time maintained the pre-eminence of a simply iodized collodion for the tannin plates, has recently come to the conclusion that a bromide in dry plates materially accelerates ; and with the honest straightforwardness which always distinguishes his writings, at once avows this change in his views on the sub ject, and explains the cause. We had hoped to relate the re sults of some further personal experience in this direction; but must delay it for the present. In the meantime, there fore, we lay before our readers these few brief notes on the subject. We shall be glad to learn from time to time the results of their experience. “ OUR LIVERPOOL CONTEMPORARY.” We have to claim the indulgence of our readers for a few moments, whilst we make one or two explanations or com ments upon a matter we should prefer to pass in silence, । were it not for the fact, that silence would, probably, be mis-
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