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466 THE PHOTOGRAPHIC NEWS. [June 26, 1891. PHOTOGRAPHY IN GERMANY. BY HERMANN E. GUNTHER. Agar-Agar once more—New Process of Making Print ing Plates—Blisters in Gelatino-Bromide Prints— Platinum Printing—Who is Rembrandt? Agar-Agar once more.—With reference to my own remarks on agar-agar as a substitute for gelatine in emul sion making on page 381, I may add here the observations of V. Schumann with regard to the same subject which this eminent investigator published some time ago in the Phot. Wochenblatt (vol. xi., p. 164). He writes:—“ Agar- agar bromide emulsion is sensitive from about 6} F. up to the ultra-violet, much like the gelatino-bromide emulsion, the lines being clear. Agar-agar emulsion shows scarcely any tendency to adhere to the glass plate, except at the edges. The plates are entirely matt. Some emulsion poured on glass, dried, then washed and again dried, was totally fogged, though it gave a ■weak image of the spec trum at an exposure of fifteen minutes (paraffin lamp). Agar-agar soaked with ammonium bromide and cooked dissolved little or none at all. Agar-agar cooked for a longer time, after the addition of bromide, emulsified, and poured at once unwashed on the plate, gave, when the plate, after washing, was treated slightly with alcohol, a rather good negative, provided it was not washed. In the bath following the fixing bath, the agar-agar film left the glass plate, and was lost beyond recovery.” New Process of Making Printing Plates.—Mr. Fr. Winter- hoff, of Cologne, has patented a process of making glass printing plates for typographic and lithographic purposes, which will, I think, be of interest to photo-lithographers. It consists in the following:—A glass plate is coated with a sensitive solution of asphaltum, or with bichromated gelatine, and dried ; a print is then taken from any print ing plate—from a negative, forinstance—on a well-prepared transfer paper, which is then transferred to the glass plate provided with the sensitive layer. The transfer paper is then removed, and the transferred print on the glass plate dusted with metallic powder—for instance, with bronze or leaf metal—when the plate is well cleaned. It is then exposed to sunlight for about half an hour, and washed with turpentine, which dissolves the unexposed parts of the layer, whilst it leaves unaltered those portions which have been exposed to light. The plate is then etched very deeply with fluoric acid for about half an hour, rinsed, and cleaned, when it may be used as a printing plate. From this plate, transfers may be made at any time, to be transferred to stone or to zinc, or the plate may itself be employed directly as a printing plate without fear of wear and tear. These plates afford a very practical substitute for the expensive lithographic stones or zinc plates. Blisters in Gelatino-Bromide Prints.—Blisters are some times met with in work with gelatino-bromide paper. To avoid them, the Photogr. Archiv suggests the following procedure. It is necessary to use the water and the various baths as cold as possible, and to do the work in a laboratory the temperature of which is not above 68° F.; use should also be made of alum. After development, the print is washed for a few seconds in two water baths, when it should be placed for three minutes, picture side down, in a bath of Water ... ... ... ... ... 200 c.c. Alum ... ... ... ... ... 12 grammes Common salt ... ... ... ... 6 ,, Soda 1 gramme The print is then allowed to drain, and, without washing, placed in the fixing bath. The latter consists of No. 1.—Water ... ... ... ... 200 c.c. Hyposulphite of soda 30 grammes No. 2.—Water ... ... ... ... 40 c.c. Alum ... ... ... ... 12 grammes The mixture of the two solutions is allowed to stand for a day. In this bath the print should remain five minutes in summer and fifteen minutes in winter, during which time it should be repeatedly turned. It is then, without washing, placed in the already used alum bath, with the film side down. This alum bath should not be used again. Platinum Printing.—R. Wischeropp recommends the following platinum printing-out process. It is essen tial to use a chemically pure ferric salt, and to dry the solution as quickly as possible after its application to the paper, in order that it may not penetrate into the paper. For this purpose a dry box is necessary, kept at a tem perature of 133° F., so that the prepared paper placed in it may dry within two minutes. The solutions required in this process are, according to the Phot. Nachrichten, the following:— Solution A. Sodium ferric oxalate Sodium oxalate solution (3 : 100) Potassium chlorate Solution B. Distilled water Potassic chloro-platinite ... 40 grammes ... 100 c.c. ... Od gramme ... 60 c.c. ... 10 grammes In Solution A the solutions, which are kept separately in the Pizzighelli process, are united; then the addition of glycerine, which is declared needless by the author, is left out. Solution B keeps indefinitely, whilst Solution A should be renewed from time to time. To sensitise one sheet of arrowroot paper, 8 c.c. of Solution A and 5 c.c. of Solution B are required. The sheets of paper are fastened with drawing pins to two wooden strips, one of which projects sufficiently to enable the sheet to be placed on the edges of the dry box. The latter is made of sheet iron, and is warmed by a gas boiler, the paper being sus pended in it in such a manner that the second wooden strip remains about four inches distant from the bottom of the box. The solution is quickly applied to the paper with a bristle brush, spread with a round badger-hair brush, and then the sheet is quickly hung therein. In order that the paper, after drying, may give brilliant prints, it should be kept for some time previously in the dark room. It is then laid, together with the negative, in the printing frame, and covered all over with india-rubber cloth. As soon as the desired tone is attained, the print is fixed in a solution of hydrochloric acid 1: 80. The fresher the paper, and the more quickly it is worked, the more beautiful will be the tones of the prints. For this reason it is advisable to print in direct sunlight. Who is Bembrandt ?—A very remarkable book has been published of late by a young literary man, Max Lautner, of Breslau, which has excited much attention in artistic circles in this country. In this work the author endeavours to demonstrate that most of the celebrated paintings attributed hitherto to Rembrandt are really the work of one of his mosttalentedpupils, namely, of Ferdinand Bol, of Metheln, near Antwerp, whose name has been scratched or painted over on his works, and the name of Rembrandt substituted. In his researches, the author has made use of photography, which has been able, so to say, to look through the various layers of colour down to the ground of the painting, and there to detect any
