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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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54 THE PHOTOGRAPHIC NEWS. [JANTARY 26, 1883. answers very well, and is by many operators preferred to bank posts ; it gives a smoother and brighter surface than the latter, but, being softer, it does not stand washing so well. Sensitizing.—The standard formula for the preparation of the sensitizing coating is—■ Gelatine 3 parts Bichromate of potash., 2 „ Water ... ... 50 „ The gelatine is soaked in the water till soft, and then dissolved with heat, the bichromate in powder is added and stirred till dissolved ; or the gelatine may be dissolved in half the quantity of hot water, and the bichromate in the other, and the two solutions mixed. The proportions will depend upon the quality of the gelatine and the prevailing conditions of temperature and humidity of the atmosphere. More of a soft gelatine than of a hard will be required, and in hot weather it will be advisable to mix in a proportion of strong gelatine and increase the quantity to five parts, while the bichromate may be reduced to one part. The addition of a small quantity of liquor ammmonia will also probably be an advantage in enabling the paper to be kept longer in good order, but we have not found it necessary. The above solution is strained through one or two folds of cotton or woollen cloth into a dish or trough, which should be placed in another containing hot water. For sensitizing large sheets we use a copper trough about eight inches wide, two inches deep, and long enough to take the width of the largest sheet to be sensitized. This trough stands in an outer one of the same metal, rather larger every way, and supported on legs about ten inches high; so that, if necessary, a lamp or small stove may be placed below to heat the water contained in the trough and keep the gelatine solution liquid. The surface of the solution having been skimmed to clear it of froth and bubbles, the paper is passed over the surface of the liquid gelatine, so as to obtain an even coat ing free from air-bubbles, and is then drained and hung up to dry in a dark place free from dust. When large quantities of paper have to be constantly prepared, it is convenient to have a drying-box which may be made of galvanised sheet iron fastened on a wooden framework and heated from below with gas, oil, or charcoal, a vent being made above to cause a current of air, and give exit to the damp vapour. Fixed at each side of the box are one or two wooden cross-pieces, with notches at about six inches apart, to receive the thin wooden slips, on which the sensitized paper is fastened with clips or pins. The lower series of notches must come between the upper ones, so that the drippings from the upper sheets may fall clear of the lower ones. The wooden slips may be varnished and greased with cocoa butter, or other suitable material, as recommended in the Autotype Manual for sensitising carbon tissue, but we have not found it necessary. As soon as the first coating in dry, a second is given in the same way ; but in hanging up the paper the second time, that end should be uppermost which was lowest be fore, so as to as far as possible equalise the coating. Before use, the paper should be glazed by passing it through a lithographic or copper-plate press in contact with a plate of polished metal. The press and zinc plate or stone which serve for inking the transfer prints will answer perfectly for this also. The glazing is of impor tance, and adds very much to the sharpness and delicacy of the lines. The prepared paper should be of a fine, bright, even yellow colour, and free from streaks of uneven coating, bubbles, or spots of dust and dirt. The coating of gelatine should not be too thick, or the finer lines will be apt to wash away, while the strong lines will have a tendency to absorb too much moisture in damping and spread out in transfer. In the inking-up methods, too thick a coating of gelatine will swell too much, and be difficult to ink. If, on the other hand, the gelatine coating be too thin, when inking in the press the ink may be forced into the substance of the paper, staining the ground and making it difficult to get clean transfers. A moderate thickness gives the best results by either method. The sensitized paper will, under favourable circum stances of dry cool weather, keep good for a week or longer—we have known it keep good for a month ; but in hot damp weather, such as is experienced in the hot and rainy seasons in some parts of India, it will not keep for more than a day, and must be used as soon as made. When circumstances permit, it is preferable not to use it quite fresh, but a day or two old. In using this paper in the usual washing-off method, the whole of the unaltered gelatine should dissolve away and leave the paper perfectly clear of gelatine except in the lines under the ink. This entire removal of the gelatine has, however, been objected to by many operators as not giving the necessary “ grip ” in the process of transfer on stone, though 1 have not observed that this defect causes any difficulty on either grained or polished zinc. It has therefore become the more general practice to use a paper prepared so that a coating of insoluble colloid may remain on the surface after development of the transfer print. The first method of this kind was that published by Mr. J. W. Osborne, of Melbourne, in 1859, a little earlier than the Southampton method, and it is, I believe, still used with admirable results in the Australian Colonies. I am indebted to Mr. Fraser S. Crawford, of the Surveyor-General’s Office, Adelaide, for the following par ticulars of the preparation of the photo-transfer paper according to Osborne’s method. 1,600 grains of Nelson’s opaque gelatine are dissolvedin 10 ounces of water, and 880 grains of bichromate of potash also in 10 ounces of water. The two solutions are mixed, and when Cooled to 90’ F., 4 ounces of albumen are added, and the mixture strained through fine muslin into a tin trough 18 inches long, 3 inches wide, and 1} deep, one side being bent round as shown in the figure. The paper used is Rive’s thin photographic paper, and the manner of coating is as follows :—The operator takes a sheet of paper by two adjacent corners, and holds it over the trough while an assistant presses it down into contact with the surface of the liquid with a wooden scraper; the operator then draws the paper slowly towards him (see figure), the surplus solution is drained off for a few seconds, and the sheet hung up to dry, and, when dry, is passed under the press on a clean stone to smooth the surface. Mr. Osborne particularly recommends this mode of coat ing paper as economical, ensuring regularity of coating, and enabling the liquid to be retained at the desired tem perature without difficulty. He also lays great stress on the freshness of the albumen, the object of which is to be come coagulated by the treatment of the transfers after inking with boiling water. This layer of coagulated albumen is the distinguishing feature of his method, in-
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