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The photographic news
- Bandzählung
- 27.1883
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- 1883
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- Hochschule für Grafik und Buchkunst Leipzig
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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
- Ausgabe No. 1270, January 5, 1883 1
- Ausgabe No. 1271, January 12, 1883 17
- Ausgabe No. 1272, January 19, 1883 33
- Ausgabe No. 1273, January 26, 1883 49
- Ausgabe No. 1274, February 2, 1883 65
- Ausgabe No. 1275, February 9, 1883 81
- Ausgabe No. 1276, February 16, 1883 97
- Ausgabe No. 1277, February 23, 1883 113
- Ausgabe No. 1278, March 2, 1883 129
- Ausgabe No. 1279, March 9, 1883 145
- Ausgabe No. 1280, March 16, 1883 161
- Ausgabe No. 1281, March 22, 1883 177
- Ausgabe No. 1282, March 30, 1883 193
- Ausgabe No. 1283, April 6, 1883 209
- Ausgabe No. 1284, April 13, 1883 225
- Ausgabe No. 1285, April 20, 1883 241
- Ausgabe No. 1286, April 27, 1883 257
- Ausgabe No. 1287, May 4, 1883 273
- Ausgabe No. 1288, May 11, 1883 289
- Ausgabe No. 1289, May 18, 1883 305
- Ausgabe No. 1290, May 25, 1883 321
- Ausgabe No. 1291, June 1, 1883 337
- Ausgabe No. 1292, June 8, 1883 353
- Ausgabe No. 1293, June 15, 1883 369
- Ausgabe No. 1294, June 22, 1883 385
- Ausgabe No. 1295, June 29, 1883 401
- Ausgabe No. 1296, July 6, 1883 417
- Ausgabe No. 1297, July 13, 1883 433
- Ausgabe No. 1298, July 20, 1883 449
- Ausgabe No. 1299, July 27, 1883 465
- Ausgabe No. 1300, August 3, 1883 481
- Ausgabe No. 1301, August 10, 1883 497
- Ausgabe No. 1302, August 17, 1883 513
- Ausgabe No. 1303, August 24, 1883 529
- Ausgabe No. 1304, August 31, 1883 545
- Ausgabe No. 1305, September 7, 1883 561
- Ausgabe No. 1306, September 14, 1883 577
- Ausgabe No. 1307, September 21, 1883 593
- Ausgabe No. 1308, September 28, 1883 609
- Ausgabe No. 1309, October 5, 1883 625
- Ausgabe No. 1310, October 12, 1883 641
- Ausgabe No. 1311, October 19, 1883 657
- Ausgabe No. 1312, October 26, 1883 673
- Ausgabe No. 1313, November 2, 1883 689
- Ausgabe No. 1314, November 9, 1883 705
- Ausgabe No. 1315, November 16, 1883 721
- Ausgabe No. 1316, November 23, 1883 737
- Ausgabe No. 1317, November 30, 1883 753
- Ausgabe No. 1318, December 7, 1883 769
- Ausgabe No. 1319, December 14, 1883 785
- Ausgabe No. 1320, December 21, 1883 801
- Ausgabe No. 1321, December 28, 1883 817
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Band 27.1883
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284 THE PHOTOGRAPHIC NEWS. [Mat 4, 1883. NOTES ON PHOTOGRAPHY. BY E. HOWARD FARMER. Lecture XX.— PLATINOTYPE Printing. This process was invented, and has been perfected, by Mr. Willis. Suitable paper is sensitized with the following mixture:— Eerric oxalate (Fe2 (C:0,)3) ... ... 60 grains Potassic chloro-platinite (2KC1,PtCl2) ... 60 „ Water ... ... ... ... ... ... 1 ounce The materials are mixed immediately before use, and spread over the paper, which is then dried with the aid of heat, and is ready for printing. To preserve the sensitive paper, it is absolutely necessary that it should be kept dry, and for this purpose tin cases containing asbestos saturated with anhydrous chloride of calcium are employed; it is, however, better to use it as soon after sensitizing as possible. The time occupied in printing is about one- third that taken with silver ; the time of exposure can be judged either by looking at the print when the image is seen of a brown colour on a yellow ground, or with an actinometer ; if the printing be continued too long the brown colour lightens again from reverse action (solariza tion). To keep the paper thoroughly dry whilst printing, vulcanized gutta-percha pads are used, and, after printing, the prints are placed at once into a calcium tube. The best results are obtained with negatives having a full scale of gradation, from opaque high lights to bare glass shadows. The action of light is to reduce the ferric- oxalate on the paper to the ferrous condition, the platinum salt undergoing no visible change. To obtain the platinum image, the following solution is made :— Potassium oxalate (K,(C,0,) ... 120 grains Water 1 ounce Acidified with oxalic acid. This is placed in an enamelled iron dish, and heated with a gas burner to about 180° or 200° F. (nearly boiling) ; the exposed prints are then slowly drawn through the hot solution, sensitized side downwards. To facilitate this, the paper may conveniently be held at two ends, and weighted between with a thick glass rod ; the development takes place, and is completed almost immediately the paper touches the liquid, the reaction being as follows :— 3(2KCI,PIC1,)6Fe(C,0,)=3Pt-2Fe,(C,0,)3+Fe,Cl,-+6KCI The action does not occur so long as the salts are in the dry condition ; but immediately the print is immersed in the oxalate of potash, the ferrous oxalate is dissolved, and at once reduces the platinum salt with which it is in con tact. After development, the prints are washed (not fixed) in water acidulated with hydrochloric acid, until every trace of colour due to iron is gone, then in water, and finally placed between clean blotting-paper to dry. Over-exposed prints can be cured to some extent by using a colder developing bath, and under-exposed prints by using a hotter bath. Paper which has deteriorated by damp, or by being kept too long, is useless, and cannot be restored. Flatinotype prints are probably as permanent, if not more so, than those produced by any process known with the same basis. Prints on wood, silk, and other fabrics, can also be obtained. To work the process, a licence and the requisite mate rials must be obtained from the Flatinotype Co. W hether from a theoretical or a practical point of view, or from the results obtainable, Flatinotype is the most perfect of pro cesses, and should be familiar to every photographer who loves his art. ASTRONOMICAL PHOTOGRAPHY. Mr. Edward C. Pickering, the Director of the Harvard College Observatory, thus writes in Nature :—The important part that photography is likely to play in astronomy renders it desirable that an opportunity should be afforded to astronomers to acquaint themselves with the improvements continually made in this branch of their science. This could best be done by the establishment at convenient places of collections, designed to exhibit the progress of photography as applied to astronomical observations. The Harvard College Observatory has some special advantages for forming such a collection, since it already possesses many of the early and historically important specimens which would naturally form part of the series. Among these may be mentioned four series of Daguerreotypes and photographs of various celestial objects taken at this Observatory. These series were respectively undertaken in 1850, 1857, 1869, and 1882. At present, the astronomers of the United States have no ready means of comparing their own photographic work with that done in Europe, or even with that of their own country men. The proposed collection of photographs, s® far it could be rendered complete, would greatly reduce the difficulty. It is therefore desired to form, at the Harvard College Observatory, a collection of all photographs of the heavenly bodies and of their spectra which can be obtained for the purpose; and it is hoped that both European and American astronomers will contribute specimens to this collection. Original negatives would be particularly valuable. It may happen that some such negatives, having slight imperfections which would limit their value for purposes of engraving, could be spared for a collection, and would be as important (considered as astronomical observations) as others photographically more perfect. In some cases, astronomers may be willing to deposit negatives taken for a special purpose, and no longer required for study, in a collection where they would retain a permanent value as parts of an historical series. Where photography is regularly employed in a continuous series of observations, it is obvious that specimen negatives only can be spared for a collection. But in such cases it is hoped that some duplicates may be available, and that occasional negatives may hereafter be taken for the purpose of being added to the collection, to exhibit recent improvements or striking phenomena. When negatives cannot be furnished, glass positives, taken if possible by direct printing, would be very useful. If these also are not procurable, photographic prints or engravings would be desirable. In connection with the photographs themselves, copies of memoirs or communications relating to the specimens sent, or to the general subject of astronomical photography, would form an interesting supplement to the collection. A part of the contemplated scheme will involve the preparation of a complete bibliography of the subject, including a list of unpublished photographs not hitherto mentioned in works to which reference may be made. The expense which may be incurred by contributors to the collection in the prepartion and transmission of specimens will be gladly repaid by the Harvard College Observatory when desired. EMULSION PROCESSES FOR BEGINNERS. BY M. LOCKETT.* In accordance with a request that I should give an account of my experiences with emulsions, I will now do so, hoping that I may be of some little benefit to others who may wish to follow in the same line ; but at the same time, I must say that I have nothing new to briug forward, no new process, or anything more than has been already published. What I have most to impress on your minds is the necessity for being careful in the manner of doing it, remembering that “ what is worth doing at all, is worth doing well; ” and that in matters photographic we must not depend too much on rule-of-thumb, or we must not expect much success to attend our labours ; and more especially in the com mencement of the process—the preparation of the plates—which I have to my cost found out not once, nor half-a-dozen times. In the first place, as collodion emulsions are not in great use now, I shall only just touch on the way in which I succeeded best—I believe, that of Colonel Stuart Wortley. I dissolve the pyroxylins and Balts in ether and alcohol in proper proportion for the required quantity, and pour out to set, not too much, but enough to cut up into small pieces ; these I put into a bottle to cover with an acid solution of AgNOs, 80 grains to 1 ounce water for two hours, afterwards drain, and wash in water by placing them on a piece of muslin stretched over a paraffin lamp • Read before the North Staffordshire Photographic Association.
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