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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
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- SLUB Dresden
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- Public Domain Mark 1.0
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- http://digital.slub-dresden.de/id1780948042-18630000
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- oai:de:slub-dresden:db:id-1780948042-18630000
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- Parlamentsperiode
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- Bandzählung
- No. 251, June 26, 1863
- Digitalisat
- SLUB Dresden
- Strukturtyp
- Ausgabe
- Parlamentsperiode
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Titelblatt Titelblatt -
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- Register Index 619
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Band
Band 7.1863
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- Titel
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let the whole be kept in a warm, but not hot, place for a quarter of an hour, a cool kitchen oven answers the purpose well ; in the meantime raise eight ounces of distilled, or, at any rate, pure rain water to the boiling point, and pour it on the malt, soaked as above, constantly stirring ; cover the vessel and return it to a warm situation, and thus it may be left for two hours, by which time the fluid will have entirely changed its character and become sweet; it may now be allowed to cool for an hour, and then the whole con tents of thvessel should be emptied on a canvas or hair strainer, a common sieve in fact, and, when the fluid has run through, a couple of ounces more distilled water should be quietly poured on the pasty mass, and thus the infusion which it retains will be principally removed by displacement. It is very important to pay attention to the quality of the water, and negligence in this respect has in more than one instance led to the rejection of this pro cess ; of course, if chlorides or carbonates be contained in the water, which is almost invariably the case with ordinary hard water, the plates, when treated with the preservative fluid, will necessarily be rendered insensitive from the formation of chlorides or carbonate of silver, in the original plan ; the subsequent preparation, however, of the preservative fluid, by the writer’s method, will prevent the possibility of the latter salt being formed. On rest ing for a short time, the strained fluid will have deposited a thick sediment, from which the clear supernatant fluid should be poured ; it is not necessary to filter it, which is a very tedious process, and with the quantities above proposed, fluid enough may be poured off to coat three dozen stereoscopic plates. Pour the fluid, thus obtained, into a Florence flask, or such vessel, add ten drops of glacial acetic acid, agitate, place the flask in a water bath and raise to the boiling point, retaining it at this temperature until the fluid in the vessel boils well, it may then be allowed to cool. As it cools, we shall again find a fluid sediment, which, as above, may be separated by de cantation ; add half an ounce of alcohol and the preservative fluid is pre pared, requiring, however, in most cases to be strained, though it is useless to filter it, as, even when passed through a filter, it will retain its milky, emulsive appearance, which is no detriment and cannot lie removed, except ing by a circuitous, complicated process, and we all know that it is essential in photographic operations to keep the conditions as simple as possible. The subsequent steps are those common to all prepared plates, that is to say, the film of collodion is sensitized in the nitrate of silver bath, and thoroughly washed with distilled, or, at any rate, pure rain water; the preservative fluid is then [poured upon it repeatedly and in such a manner as to ensure its action upon every portion of the surface, and then, deviating from the direc tions of Mr. Macnair, the plate is introduced into a dish of soft water and allowed to soak for five or ten minutes ; it is again washed with a fresh supply of water and placed in a suitable position to drain, resting one corner on blotting-paper. In the course of half an hour it may be exposed to heat in any suitable manner in order that it might become thoroughly dry ; the plate, in fact, should be heated to such a degree as the hand will just bear, and may then be stowed away for use. Plates prepared by this process, and rigidly secluded from light, damp, and foul air, are stated to keep for at least six weeks. One of the especial characteristics of the malt process was observed to be the tenacity with which it adhered to the glass, and it occurred to the author to utilise this quality in the tannin process in which the greatest trouble is the tendency of the film to leave the glass. After a variety of experiments, which are detailed, the following was deter mined upon as the Second Process. “1. Having prepared malt infusion and strained it, add one-third bulk of alcohol. Leave to deposit, and filter. “2. Just before using, add an equal bulk of solution of tannin in water, five grains to the ounce, and again filter.” This solution was used in the usual way, and from the extracts which the author gives from his note-book, we learn that plates kept two months give good results. We may here note in the author’s experiments a somewhat unusual one, which is however stated to be successful, a tannin plate is re-dipped in an aceto-nitrate of silver bath before deve loping. The author was anxious, however, to obtain a greater degree of sensitiveness without any sacrifice of other good qualities, and bearing in mind the theoretical considerations which had predisposed him in favour of malt, he looked for another body “ not only produced from others by changes easily effected, but in itself so nicely balanced as to the forces which keep its molecules in a state of aggregation, that these can be disturbed and assume new forms by apparently trifling causes.” Such a substance he found in glycerine, and by its aid, after various experiments, he was led to the Third Process., “ The preservative solution for the tanno-glycerine process is thus pre pared Solution A. Tannic acid ... grains Water ounce Glacial acetic acid drops. Solution B. Glycerine drachm Solution A ... ... ... ,,, ... 2 drachms Water 5 which latter is poured on and off the plate in the usual manner adopted at this stage.” The addition of acetic acid was made in consequence of slight fogginess observed on certain portions of the plate during development, and it certainly remedied the evil; but the bath was in fault, aS it gave foggy results with the wet process. The author refers to this process as giving very good results for interiors, and gives an extract from his note-book to the effect that the two halves of a stereoscopic plate had respectively ten seconds and twenty seconds exposure in his drawing-room with a Dallmeyer's stereoscopic lens, No. 4 stop, on a dull day in December; both halves coming out with long development. The next process is stated to promise very rapid results, but requires great care in its management. It is called Fourth Process. The tannin and glycerine are used as before, with the addition of ten minims of formic acid to each ounce of the preservative solution, and when well mixed, which, of course, must be at the time of using, ten minims of solution of nitrate of silver, strength twenty grains to the ounce; the quantity of the two last fluids may be increased to thirty minims of each; but most extraordinary care must be taken thoroughly to wash the plates. Let it also bo observed that formic acid of the strength used by the writer, which is the strongest and purest he can obtain, has a great tendency to loosen the film bodily from the plate. Plates by this process have not been kept more than a day. . With regard to the collodion to be used with these pro cesses, Dr. Kemp expresses a conviction that any good bromo iodized collodion will answer, but he gives a formula, for which we refer our readers to his book. The nitrate bath is prepared as follows:— A. Re-crystallized nitrate of silver 320 grains Distilled water 5 ounces. B. Caustic potash (avoid ammonia) 2 grains Distilled water 1 ounce. Mix these, and, when agitated, allow the precipitate to subside, and filter; fill up to nine ounces and add acetate of soda, previously dissolved in an ounce of water, three grains with five minims of glacial acetic acid. The bath is now ready for use, and should be tested for action with a wet collo dion plate, developing with pyrogallic acid. If foggy, more acetic acid should be added, drop by drop, until the bath works clear ; but the writer has always found the above proportions give good results. It will be observed that the bath is not, as usual, saturated with iodide of silver : the first plate may suffer a little if the weather be very warm, but it is simpler and safer, for reasons which will presently be stated, to leave it thus. The washing and drying may he carefully conducted in the usual way ; 'but the author enters into minute details, both in regard to these and other manipulations, describing the methods most successful in his hands. For development he prefers the slow method with gallic acid, strengthening if necessary with pyrogallic acid and silver, or by some other of the known intensifying pro cesses. In regard to the class of negatives produced we may say that at a recent meeting of the North London Photographic Association, the chairman exhibited some of Dr. Kemp’s negatives, which were very excellent in quality, but by which of these processes they were produced we cannot state. Besides the full details of the processes of which we have given a copious synopsis, there is much incidental valuable information in the book. It is remarkably free from dog matic assertion or egotistical claims, and is written in a winning courteous spirit, well worthy of imitation. The chapter on Photography for the Scientific Tourist and Mis sionary, is devoted largely to the consideration of the methods of securing portability, the use of either the collo dion process, on mica plates, or of the Talbotype process being recommended. Critical Elotites. A POPULAR TREATISE ON PHOTOGRAPHY, trans lated from the French of Dr. Van Monckhoven, by W. H. Thornthwaite, Ph. D., F.C.S. London : Virtue Brothers. The original of this work consists of an excellent epitome of the author’s Traite General, compiled by two gentlemen, and corrected and endorsed by Dr. Van Monckhoven. The English edition is a free translation, with elisions, additions.
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