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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
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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. 254, July 17, 1863
- Digitalisat
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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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July 17, 1863.] THE PHOTOGRAPHIC NEWS. 343 Formula for Sensitizing Solution. Nitrate of silver 1 ounce Acetic acid ... ... ... ... bounces' Distilled water 10 Iodide of potassium 2 grains. Lay the albumen plate along one side of the glass dish, then raise this side and pour into the inclined side a sufficient quantity of the bath ; with a dexterous move raise the inclined side so that the fluid may flow over the albumen film in one quick continuous layer. By this contrivance all lines or marks of stoppage are avoided. This is a very necessary provision here; for the slightest hesitation or stoppage will infallibly show its effect on the negative. About half a minute will be sufficient to coagulate the albumen and-to sensitize the film.. The operation is performed in the dark room. After sensitization the plate is removed from the bath by raising it first with a bent silver hook, and then seizing it by one corner with the hand. It is then washed under the tap, and left to soak in a dish of distilled water until the next plate is prepared. The quantity of acetic acid in the above formula may be diminished in many instances ; its object is to prevent fogging, but it diminishes sensitiveness at the same time. If with half the quantity no fogginess supervenes, this quantity will be quite enough: in this manner, that is, beginning with a small amount of acetic acid, and gradually increasing until fogging ceases, more rapid effects may be obtained in the exposure. When the sensitized plates are kept long, they undergo a species of de composition which induces fogginess ; the fresh plates, there fore, are in the best condition for producing normal effects with the greatest rapidity, because the sensitizing bath requires the least amount of acid. Blisters are apt to arise in the film by immersion in the sensi tizing bath, or during the subsequent operations. These are frequently owing to the imperfect cleaning of the plates, or in the clumsy flowing of the albumen. Gummy substances are sometimes added to the albumen in order to render it more ad herent or less contractile. The amount of exposure will depend on the conditions of light, the focal length of the lens, and the sensitiveness of the albumen. In the bright light of spring an exposure of two or three minutes with a pair of stereoscopic lenses will, in general, be amply sufficient. Experience alone can determine the amount of time required in a given case. Development of the Image. The plate is placed in a glass dish or in one of gutta percha, and the developer is poured upon it by the same mode of manipulation as just described to be used in the sensitizing operation. Formula for the Developing Solution. Gallic acid ... ... ... ... 8 grains. Distilled water (90° Fah.) 2 ounces. Previous to immersion in the above solution the plates are subjected to the softening action of a warm dilute solution of gallic acid (one grain to the oz. of distilled water), for half an hour. After this the plate is flowed with a sufficient quantity of the above solution containing five or six drops of a solution of nitrate of silver two per cent, strong. The imago will soon begin to appear, and will proceed until the Vigour of the print is satisfactory. The development is not so soon com plete as in collodion operations, the time required varying from a few minutes to forty minutes or an hour. Almost any amount of exposure can bo made to yield a good picture, by adapting the developing solution in accordance with the exposure. If the plate Ims been under-exposed, more silver will have to be used; if over-exposed, less will bo found to bo all that is neces sary. Silver from the sensitizing bath might bo .used, but in this case it must contain more acetic acid. The weak solution above prescribed is to bo preferred; and if there is a tendency f to fogging, add a few drops of acetic acid to counteratt-the effect. As soon as tho shades are sufficiently dense, the plate is removed from the bath, well washed in many waters, and then the image is fixed in a solution of hyposulphite of soda. No varnishing is required, because tho albumen film is quite hard of itself. O ABOUT DRY PLATES. BY J. MILTON SANDERS, M.D., LL.D. Arrmovon much has been written upon the subject of dry plates, still it has not been exhausted, for the process has yet to be discovered. The process I have followed for years I now describe, together with the recent improvements I have made. The collodion for this purpose must be prepared in the following manner:—In eight fluid ounces of alcohol, put eighty grains of gun cotton. Allow the cotton to remain in the fluid long enough to become thoroughly saturated, then you must pour on it eight fluid ounces of ether; shake, and the cotton will dissolve. Now add to it eighty grains of iodide of cadmium, and sixty grains of the bromide of the same metal, shake until the salts are dis solved and your collodion is finished. This collodion should remain standing in a shaded place for about a. week, before it is' fit for dry plates. When ready to use, pour out one or two ounces of it in your collodion vial, and add sufficient tincture of iodine to it to change it to a dark brandy red ; but the great body of the collodion should not be thus treated, or the iodine will deterioriate in a few days. To prepare the dry plates proceed as follows:—Sensitize your plate with, the above collodion in a fifty-grain bath, leaving it in the bath at least three minutes before you con sider it thoroughly sensitized. Now take it out, hold it under the tap until all the nitrate of silver is washed off, and then pour upon it a filtered solution of twenty grains of tannic acid to the ounce of water* I previously used a thin solution of albumen, but I find that tannic acid is fully as good, if not better. Having poured off and on the tannic solution several times, drain the plate well, and place it away in your dark box. Having placed the plate in your camera, give it about twice the length of exposure you would a wet plate. Return to your dark room, take the plate from the holder, and hold it under the tap until the tannic solution is washed off, and the collodion surface is thoroughly wetted. Now pour over it, or flow upon it, a fifty-grain solution of nitrate of silver, saturated with iodide of that metal t (or with some of your bath solution.) Drain it slightly, and develop with the fol lowing new developer:— Water ... 20 ounces. Sulphate of iron 1± do. Dissolve the iron, and with ammonia produce a slight pre cipitate in the solution. Then add— Acetic acid, No. 8 ... 2 ounces. — Filter.+ Under this developer the picture will soon exhibit itself clear and intense; but if it should not come out sufficiently intense, intensify it further with bichloride of mercury, afterwards flowing upon it some diluted acqua ammonia to blacken the bichloride. I would mention that the developer given above will answer an acmirable purpose for all wet plates. It brings out the picture beautifully clear and trans parent, much more so than if the free sulphuric acid were allowed in the developer. I_would further state that although I may be thegftrst person to avail myself of this form of developer, thal’I was/induced to do so through a suggestion of Professor Seely’given in the April number of tho American Journal of Photography.^—American Journal. St. Domingo, W. I., Hlaf, 1863. THE ESTHETICS OP PORTRAITURE. by n. DISDERI. (Continued from p. 332.) The group portrait is often very much abused ; and off all the different kinds of portraits, it is the one to which the very * The tannic acid should be filtered in vacuo, if possible, for if exposed but a brief time to the air, a reaction takes place, oxygen is absorbed, car bonic acid given out, and gallic acid is formed. This latter acid will play the devil with your plate 1 f We must caution our readers against following this suggestion. The iodide is not only useless, but mischievous.—Ed. Photo. News. + This developer must be used freshly made, as age soon deteriorates it. 2 A similar developer has been used in England for years, and repeatedly published.—Ed. Photo. News.
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