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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
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- Englisch
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- F 135
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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. 1306, September 14, 1883
- Digitalisat
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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band
Band 27.1883
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- Titel
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SEPRMBER 14, 1883. J THE PHOTOGRAPHIC NEWS. 583 B Hictiouarg of Photography. ALUMENIZED PAPER (Printing on).—Continued. Senitizing.—Having dusted the dish, pour out the solution to the doth of half an inch equally all over the vessel ; brush the surfao of the paper with a large flat camel-hair brush ; lay the Papersteadily (albumenized side downwards) on the surface of the snsitizing bath in such a manner that air-bubbles are not formd, neither the silver allowed to touch the back ; this may he acomplished by floating in the manner described in the last chipter on albumenizing. As soon as the paper has been laid dowi, it should be lifted by means of a glass rod at one of the corers, and examined; if the operation has been successful, there willbe no air-bells attaching themselves to the sheet, but should thee be any, they may be easily removed with the glass rod, or blovn off; the sheet is again replaced on the bath, and allowed to ronain long enough to become fully sensitized. The length of tine will be found to vary. For instance,-if we are using paper wich has been albumenized for a few months, three minutes will b found to be long enough ; but if the paper is freshl / prepared, i repels the solution, and will take as long as five minutes in warm weather; also in cold weather a longer time will be re quired than is necessary when the temperature ranges from 60° to 760 F. When the sheet is down on the bath it will be seen that it does not lie perfectly flat. After the space of a little while it becomes absorbed with moisture, and will present an even surface. When that period arrives, whether it requires three minutes or ten, the sheet is ready for removal. liaise the farthest corner of the’ sheet to the left, off the solution, by means of the glass rod. Seize it by the left hand, raising the sheet slowly; now take the nearest corner with the right hand and draw the sheet steadily and slowly over a glass rod fixed at the end of the dish ; if this is carefully done, all excess will be removed, and the sheet will be dry in a few minutes ; suspend it from one corner (albumenized side outward) by moans of one of the American clips in the drying room. By the time ten sheets have been floated, about 290 grains of silver nitrate will have been converted into chloride or absorbed. This should be replaced by means of 4 fluid ounces of a strong stock solution of nitrate of silver, made by adding 3G fluid ounces of water to G ounces of re-crystallized nitrate of silver. If a less quantity than ten sheets are floated, a proportionate quantity of the strong solution should be added. So much has been said by some of our best photographic printers both for and against the practice of fuming the paper with ammonia, and, considering that our American cousins adopt it almost exclusively, we will briefly describe the operation. When ammonia hydrate (NH 4 0H), known as liq. ammon. fort, s.g. -880, is exposed to the atmosphere, pungent fumes of gas are given off. If these fumes are collected in a closed box, and sensitized paper subjected thereto, the sensitiveness will be nearly doubled ; the colour of the print will be inclined to violet, of course depending on the length of time it is acted upon. The toning will also take place in nearly half the time require! for un-fumed paper. Finally, the result will be quite equal in every respect to paper not so treated. The reasons why we think fuming is not more generally adopted in this country are : firstly, because the fuming cupboard or box is a trouble to make; secondly, because the commercial article as obtained from many places is not up to the standard; and thirdly, partly as a result of the two first reasons, because many of those who have tried it have failed. We have seen all sorts of contrivances used; in one case a cup board was requistioned, the sheets were hung up by means of clips some sixty inches from the floor, whilst a basin containing an indefinite amount of the liquid was placed on the floor, the door shut, and the action continued for a quarter of an hour; the drawback to this plan was, that the paper was not acted upon equally, hence a mixed batch of prints was the result. Wo have since seen an arrangement which has been in constant use for some years, therefore can speak as to its practicability. An ordinary pine box measuring 25 by 20 inches, by 18 inches deep, to which a lid is attached, having a piece of moulding screwed on; also strips of felt tacked on to the upper edge of the box to prevent the escape of gas when shut; inside, and a couple of inches from the top, a light wooden frame covered with coarse netting is hinged so as to allow of the stock-bottles being taken in and out; a saucer on the bottom to contain the liquid completes this simple but effective arrangement. To prevent failure and disappoint ment, attention should be given to one or two essential points. Purchase the ammonia solution in Winchesters, and keep them well stoppered. Pour out a measured quantity (say one ounce) into the saucer just before starting the fuming ; this quantity will be found sufficient for half-a-quire of paper. Always keep the lid on the box, except when changing paper. Be sure the paper is quite dry before it is placed in the box. Ascertain from each sample the correct time to fume ; give it that time, and no more. To those who have never tried fuming we would say : Give the first sheet thirty seconds ; cut off a small piece, and expose to daylight. If the colour be reddish—as it darkens in the light— the time has been insufficient; it will be quite safe to put it back in the box for a minute longer. Another small piece may be cut off and tried as before ; this time it may first print grey, after wards becoming purple ; this is an indication that the paper is sufficiently fumed for all ordinary purposes. When there is much moisture in the atmosphere, some samples of paper show a peculiar mottled effect, although the purple colour has been reached. Such a sample of paper will produce the very best results by floating five or six minutes on a weak sensitizing bath, and prolonging the fuming until the paper will print a slatey blue ; this may require from five minutes to twenty. When the paper is acted upon too long, also when not quite dry, a metallic lustre will pervade the whole print. Such prints cannot be made to give a satisfactory tone ; neither can a good surface be pro duced by the after-operations of rolling or burnishing. As soon as the sensitizing and fuming are completed, the paper should be packed away in a dry place ; for if it is allowed to remain lying about the room, it will soon discolour; but if it is rolled up tightly, or cut up and placed under a heavy weight, it may be preserved seme three or four days (except in sultry weather) without any apparent colouration. Even after a week it will do for plain printing. If it is thought desirable to preserve it a longer time than a few days, it may be kept white between sheets of blotting-paper which have been passed through a six or seven per cent, aqueous solution of sodic carbonate. Both the sensitized and sodic papers require to be dry and kept under pressure in a dry place. The great advantage in this plan is, that the prints do not require any longer toning than usual. Another plan of fuming is to submit the felt pads to the action of ammonia, these being kept in an ammonia cupboard and changed from time to time; or the pads may be made in the form of flat bags, to hold carbonate of ammonia. Ammonia pads are used a good deal in Germany. There is a plan of preserving by re-floating the paper after it has been dried on an acid bath for a short time; it is then re-dried, and packed away under pressure ; citric or tartaric acid is usually employed for this purpose. Some photographers pre fer adding the acid to the sensitizing bath to save time ; but we should not recommend the beginner to do so. If he wished to try an experiment in that direction, the following will be found to answer :— Picked gum-arabic 2 ounces Dissolve in water 80 » Add citric acid 2 » Tartaric acid 2 „ Float the back of the paper on the above mixture for two minutes, dry, and pack away in a dry place ; paper so prepared should keep for one year at least. It w ill require fuming before it is used, and should not be toned in the same gold toning bath used for freshly-prepared paper. One thing will soon become evident to the tyro, that is, that freshly-prepared sensitive paper is not capable of withstanding the deleterious action of the atmosphere for any great length of time ; therefore, whenever he desires to preserve it as white as freshly-prepared, this fact must be borne in mind. ROYAL CORNWALL POLYTECHNIC SOCIETY. The following is the list of medals awarded in the photo graphic section on the 10th inst:— Professional:—1st silver, McLeish ; 2nd silver, H. P Robin son, W. J. Byrne, and Cobb and Son. 1st bronze, Johnson Bros., and J. M. Browne. Amateur .-—1st bronze, E. Brightman and J. R. Holmes ; 2nd bronze, Rev. A. Malan. Photographic Appliances:—1st silver, Geo. Hare; 2nd bronze, W. H. Oakley. Full report of the Exhibition, which has been very successful, will be given in our next.
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