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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
- Sprache
- Englisch
- Signatur
- F 135
- Vorlage
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- Hochschule für Grafik und Buchkunst Leipzig
- Digitalisat
- SLUB Dresden
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- Public Domain Mark 1.0
- URN
- urn:nbn:de:bsz:14-db-id1780948042-188300004
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- http://digital.slub-dresden.de/id1780948042-18830000
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- oai:de:slub-dresden:db:id-1780948042-18830000
- Sammlungen
- Fotografie
- LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
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- Parlamentsperiode
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- Wahlperiode
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- Bandzählung
- No. 1313, November 2, 1883
- Digitalisat
- SLUB Dresden
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- Ausgabe
- Parlamentsperiode
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- Wahlperiode
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Zeitschrift
The photographic news
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- Titelblatt Titelblatt I
- Register Index III
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- The photographic news
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Nor is it necessary to stop at streets and buildings. The City companies must possess a host of treasures in the way of quaint documents and relics. Probably these would not be parted with, but in many instances photo- graphy could be made use of, and thus a collection unique and valuable could be built up. Patent Entclligence. Grants of Provisional Protection. 4705. Richard Brown and Robert William Barnes and Joseph Bell, all of Liverpool, in the county of Lancaster, for an invention of “ Improvements in and relating to the art of obtaining by photography definite photographs to be used in the production of typographic blocks, and in the art of photo lithography and like arts.”—Dated 3rd October, 1883. 4732. John Edwin Atkinson, of Greenwich, in the county of Kent, for an invention of “ Improvements in apparatus for use in transporting and exposing sensitized photographic plates or films.”—-Dated 4th October, 1883. 4735. Walter Bentley Woodbury, of South Norwood, in the county of Surrey, for an invention of “ Improvements in methods of producing printing-blocks by means of photo graphy.”—Dated 5th October, 1883. Specification Published during the Week. W. R. Lake.—“ Sensitizing photographic paper and developing pictures thereon.” A communication from R. B. and B. C. West. This invention relates to photography, and has special reference to the sensitizing of the paper before printing, and the development of the print, the object of the said invention being principally to avoid the necessity for using the expensive silver solution now generally employed in this class of work. The said invention consists in subjecting the paper to be sensitized to a bath composed of potassium bichromate, magnesium sulphate, and mercuric chloride, and then, after the exposure of the sensitized paper for printing in the usual manner, subjecting the print for development to a bath composed of gallic acid, ferrous sulphate, aluminium and ammonium sulphate, and sodium hyposulphite, as more fully hereinafter described. In carrying the said invention into practice, I provide a bath for rendering the paper sensitive to light as f ollows ; that is to say, I take of potassium bichromate three parts, magnesium sulphate one part, mercuric chloride one part, and I mix and dissolve in the smallest quantity of boiling water for solution and crystallizing. Of this compound I take seventy-five grains to each ounce of water employed in the bath. The paper is floated in this bath for, say, three minutes, and is then dried in the dark ; when required for printing it is placed under the negative a sufficient time to make the lighter shades in the print visible, the time varying, say, from three to ten minutes under direct sunlight. The exposed portions of the print will be a light brown, upon a yellow ground. So soon as this condition is attained, the paper is taken from beneath the negative, and soaked in pure water, say for twenty minutes ; if the negative be very in tense, such as to require ten or more minutes of direct exposure to the sunlight, the soaking should be continued longer, say for about half-an-hour ; this is desirable because it facilitates the subsequent developing. The excess of bichromate being re moved leaves the whites of a faint yellow tint; where pure whites are required, it becomes necessary to destroy all traces of bichromate where the light has not acted, and which are not easily removed by soaking ; for this purpose the print is im mersed in a one per-cent solution of acid sulphite of sodium for one or two minutes. To prepare the developer, I take of gallic acid two parts, ferrous sulphate three parts, aluminium and ammonium sulphate three parts, and sodium hyposulphite twenty-four parts, the ferrous sulphate; aluminium and ammonium sulphate and sodium hyposulphite are each dried separately until free from water of crystallization, and are then pulverized and mixed with the gallic acid. This compound will keep and retain all its properties if protected from dampness. Of this composition I take fifteen grains to each ounce of water. To develop the print I lay it in a suitable dish, and pour upon it the developing solution to cover it, say a quarter of an inch in depth, or if several prints are to be developed at the same time, I take enough of the solution to cover all the prints. While they are in the solution I move them frequently, so as to expose them equally to the developing solution. When the develop ment of the print is completed, which will generally require about ten minutes, the excess of the developer absorbed by the paper is removed by soaking the print for half an hour in water slightly acidulated with acetic acid, after which, and when dry, the picture can be mounted. Its subsequent treatment may be substantially that usually applied to photographic prints. The sodium hyposulphite and alum in the developer exert a reducing action, which prevents the ferrous salt from becoming oxidized readily when in solution and exposed to the air, and enables the bath to be used repeatedly for several days if, after use, the precaution is taken of putting it in a tightly- corked bottle, which should be filled by the solution. Any colour from black to brown can be obtained after soaking out the developer, by immersing the print from one to five minutes in a bath composed of one part taken from the sensitizing bath and two parts of water, the time of contact with the bichromate determining the shade, and after such treatment soaking in water until the yellow tint is entirely removed. If desired to change the colour of a print to reddish brown, I subject it, after development, to a bath composed of a solution of carbonate of soda (one ounce of carbonate to one quart of water), and dry immediately. In case it is necessary to bleach the picture, it should be done after development, and before any change of colour is effected, and may be well done by subjecting the print to a solution of one partof citrate of ammonia in twenty parts of water. The paper may be prepared for sensitizing by any of the known processes, but I obtain a very good result from the following treatment; that is to say, I take paper of a good quality, coat it with a mixture composed of starch seven parts, white sugar two parts, glycerine two parts, boiling water two hundred parts, and solution of pure caustic potash sufficient to cause the coating to dry with an even surface, which will require about one-fourth part potash; the first three ingredients are mixed with a little cold water, and then stirred into the boiling water. The coating is applied by floating the paper upon the mixture in the manner usually employed in the application of albumen to paper. After drying, the paper is dipped in a two per-cent solution of acetic acid and water, and when again dried it is ready for use. In cases where the intensity and appearance of the print is of little importance, paper may be used without this treatment. Albumen paper does not under this improved process produce so good results, chiefly on account of its density. From experiments it is believed the proportions for the sensitizing and developing baths above given produce the best results, but these proportions may be varied to some extent without departing from the nature of this invention. By this process photographic prints are produced fully equal to those produced by the employment of silver, and it will be evident that the cost of the production is very much less than by the usual process employing nitrate of silver. The printing is also more rapid than by the usual process, and colours may be more readily applied to the print than when the print is prepared under the usual process. Having thus fully described the said invention, as com municated to me by my foreign correspondents, and the manner of performing the same, I wish it understood that I claim- First—The improved process of sensitizing paper for photo graphic printing, consisting in subjecting the paper to a bath composed of potassium bichromate, magnesium sulphate, and mercuric chloride, in the proportions substantially as described. Second—The improved process of developing pictures printed upon sensitized paper, consisting in subjecting the print to a bath composed of gallic acid, ferrous sulphate, aluminium and ammonium .sulphate, and sodium hyposulphite, in the pro portions substantially as described. Third—The improved process of sensitizing paper for photo graphic purposes, and developing pictures thereon, consisting in subjecting the paper upon which the print is to be made to a bath composed of potassium bichromate, magnesium sulphate, and mercuric chloride, and then, after printing, to a bath com posed of gallic acid, ferrous sulphate, aluminum and ammonium sulphate, and sodium hyposulphite in same manner, and the said baths in the proportions, substantially as described. Patents Granted in America. 286,632—Oscar H. Park, and William H. Elliott, Clarinda,
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