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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. 1274, February 2, 1883
- Digitalisat
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The photographic news
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- Titelblatt Titelblatt I
- Register Index III
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76 THE PHOTOGRAPHIC NEWS. [February 2, 1883. apparatus for ascertaining the actinic power of light.”—Dated 15th January, 1880. This invention consists in the use of the mineral phosphorescent substances for photometrical and actinometrical purposes. The phosphorescent minerals, such as sulphide of calcium, barium, strontium, or zinc, are enclosed between glass slips or glass discs to protect same from atmospheric influences, or prepared on a flexible support that can be wound round a reel. Other discs (formed of translucent and suitably coloured substance) of various transparency are situate in close contact with luminous surface, and arranged in such manner that by revolving or sliding the part of consecutive opacity transparent numbers can be interposed between the luminous surface and small telescope or other magnifier through which observation is made. Owing to the persistence of excited luminosity the apparatus is arranged so that only part of the surface is exposed at once, and the whole surface can be divided so as to enable ten to twenty exposures or more to be made, utilizing the property of phosphorescent sub stance to have the excited luminosity extinguished by the rays of low refrangibility. There is also a disc of coloured transparent media made of gelatine or collodion or glass suitably coloured, which, when interposed between the luminous surface and source of light, the luminosity is extinguished, and consequently the apparatus ready for the next observation. Having now par ticularly described and ascertained the nature and object of the said invention, and in what manner the same is to bo performed or carried out in practice, I hereby declare that I claim the invention of “ New or Improved Means of, and Apparatus for Ascertaining the Actinic Power of Light,” substantially as hereinbefore set forth and described, wherein the important point or feature is the use of phosphorescent substances for actino metrical purposes, substantially as hereinbefore described. 232. George Charles Bell, of Brooklyn, New York, United States of America, for an invention of “ A new mode or pro cess of producing photo-.elief engravings.”—Dated 19th Janu ary, 1880. The negatives heretofore employed in the production of photo relief engravings have been made from drawings or lined repre sentations of the objects to be engraved. In representing by the photo-relief process of engraving objects from nature, drawings in lines or in crayon by hand have been necessary, from which drawings negatives have been produced. The necessity for these drawings or sketches has arisen from the fact that negatives made direct from the objects themselves contain no lines, and therefore no relief suitable for printing purposes in the type press could be obtained, because engravings made therefrom would have no half tints, but would appear in solid black and white masses or blots. The principal item of expense in the production of these engravings from nature has been the cost of hand drawings, and much time is necessarily consumed in preparing these drawings, and loss of time is in many cases a matter of the greatest import ance. The chief object of my said invention is to obviate the necessity of any drawing or sketches in the production of en gravings from nature by the aid of photography, while the pro duced engravings are of superior and uniform excellence. The said invention consists essentially in the employment of surfaces provided with raised points, dots, or projections coated with a sensitizing substance, upon which facsimiles of the objects by photography are formed. I thereby obtain photographic negatives of said objects, from which negatives photographic positives are made in the usual manner, and from these positives or prints these second negatives are obtained ready for use in the ordinary pro cess of photo-relief engraving. The positive prints resemble in appearance fine mezzo-tint engraving, which effect is secured by the sensitized points or projections. These second negatives are also adapted for the production of engravings for the photo-litho graphic or other processes in which the ordinary photographic negatives or positives may be employed. The said points or pro jections are formed on the surface by the use of engraved plates, or other suitable means. The points, which are preferably numerous, are formed in straight lines, or in designs and figures of any desired description. This surface may be hard paper, or other suitable material, and may be coated with any suitable wash before the application of sensitizing substance, such as Chinese or flake white mixed with a solution of albumen, but said coating is not an essential feature of my invention ; nor is the formation of said points or projections, when the same are not sensitized, as paper with such uneven surface, and coated with a wash or pigment, is an article of commerce. The sensitizing of said points or projections may be done in any convenient and suitable manner, care being taken always that the sensitizing substance does not reach the intaglio or depressed portion of the surface. The said points may be sensitized with advantage by rubbing over the surface crystals of nitrate of silver until a sufficient quantity of the substance is transferred to the cameo or relief portion of said surface. The ordinary methods of making photographs and of producing engravings from negatives are employed ; a descrip tion of these methods is unnecessary. The said invention, it is obvious, is especially adapted to the production of illustrations from nature, of objects of which there are no drawings adapted to the various known processes now in use, and it may be em ployed with advantage in making copies of sketches, drawings, engravings, and other illustrations of natural objects. Having thus fully described my invention, and the most advantageous manner known to me of carrying the same into effect, I claim the said invention substantially as hereinbefore set forth.—Provitiondl Protection only. TWELVE ELEMENTARY LESSONS ON SILVER PRINTING. Lesson IL Photographs are usually printed upon one of two kinds of paper, viz., Saxe and Rive. The Saxe paper is obtained from a mill at Malmedy in Saxony, and is distinguished by bearing the brand of the manufacturers. It was formerly a coarser grained and tougher paper than the Rive, and has been recommended for landscapes and large prints, as it is supposed by some to be better able to withstand the washing. The Rive takes its name from a small town so named situated in the south-east of France, and may be dis tinguished by the water-mark, Rive, &c. The sheets are just a trifle smaller than the Saxe. It is said to be more suitable for small work, giving better tones and having a finer texture, but these assertions can hardly be regarded as facts at the present day, since the proprietors of both mills are continually improving their plant, with the result that paper may be obtained of both coarse and fine texture from either mill. Nearly the whole of the photographic paper used all over the universe is produced by these two mills. It is sized in the manufacture to suit the requirements of the art. To render these papers sensitive to light is the next thing which requires explanation. The paper is first of all coated with a diluted solution of albumen cen- taining the chemical salt necessary to form silver chloride when the sensitizing takes place. Although it is not expected the beginner will prepare his own paper, yet it is quite as well he should be familiar with its preparation. The usual method of albumenizing, as it is termed, is to take the white portion of fresh eggs, free from traces of yolk or germ (this is the purest form in which we find albumen) and to every gallon add the following— Dissolve in 8 ounces of water— 2 ,, ammonium chloride 1 ounce of barium chloride. To which add 2 ounces of glacial acetic acid. Add the mixture gradually to the albumen, whisk the whole to a froth with a bundle of twigs. Allow it to remain in a cool place for twenty-four hours, for the froth to subside, at the end of which period it may be strained through two thicknesses of muslin or cambric. The room intended for coating and drying should not be used for any other purpose. The fittings required are as follows:—A level bench for the dishes containing albumen; a trough to catch the excess ; a stove that will give very little dust, at the same time creating a great heat (an ordinary ironing stove fixed in the middle of the room seems to answer well); some cords stretched across the room, whereon to complete the drying; a couple of one-inch planks with three-quarter inch holes bored inclining a little downwards, and some bored quite level; a few wooden rods about 26 inches long and of the diameter to fit the holes; a packing bench ; and a few glazed earthenware pans complete the apparatus. Pour the albumen into a flat dish, being careful to avow
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