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36 THE PHOTOGRAPHIC NEWS. [July 30, 1880. A Graphic School of Engraving is to be established for the training of wood engravers. Recent “processes” of a photographic nature have caused a scare among gravers, and the consequence is a little difficulty in securing com petent men forblock-cutting just now. But photography having turned out anything but a potent rival, wood- engravers are again at a premium, and, judging by the slight progress made by “ processes ” during the past ten years, their services will be required for a long time to come. It is the inability of photography to produce the split jine that stands in the way of its displacing the engraver. When a woodcut is once printed upon paper in black-and-white, there is no difficulty [at all about reproducing it by photography. But that is not what is . required, if the engraver is to be dispensed with. The problem to be solved is to take the pencilled sketch of the artist, whether this is on paper or on wood, and to pro duce a block that will print in a type press. Of course, if this drawing were composed of black-and-white, like a pen-and-ink sketch, the camera could at once be set to the task; but draughtsmen, as a rule, do not work in this way. They may pencil some sharp black lines, but they make broad grey one oo, where the side, and not the point, of the pencil has been used. The wood engraver reproduces these latter by means of a split line, but the photographer cannot do this ; hence his inability to render the idea of the artist. Still worse is it when the drawing upon wood is done by washes of different tints ; the photographer is then yet more helpless, for it is only by a process analagous to Woodbury type or collotype that he can hope to copy at all, and we cannot, as yet, employ these methods in a type press. The practice of applying washes to wood blocks, instead of working upon them with a pencil, is very rife now-a-days, and an engraver of ability is consequently indispensable, for he is required to translate these different tints into line-work. Gopits Of the gag. OLD AND NEW FORMULA EOR COLLOGRAPHIC PRINTING. BY ADOLPHE OTT. The formulae for collographic printing or phototype have at last became very simple. The first published were those of Messrs. Ohm and Grossmann, of Munich, who professed to introduce in the second (chromated) gelatine layer, alcoholic tincture of lupulin, myrrh, balsam of tolu and benzol, besides nitrate of silver, iodide and bromide of cadmium ! Whether this recipe has ever been tried is another question. Most probably it only served the purpose of evading the patents of the ingenious Albert; a practice especially en vogue in America, where such specifications are characteristically styled “ salt and pepper patents,” i.e., one adds to a reliable composition some substances, to make it patentable, using thus the in vention of another under Government protection, without being compelled to remunerate him. In Germany, by the new law, such proceedings are fortunately not possible. The next formulas which came to my notice were those of Schrank, Vienna. He coats a ground glass plate with White of egg 2 parts Distilled water ... ... ... 1 part After drying, the plate is immersed for four minutes iu a solution of one part bichromate of potash in 15 parts dis tilled water, it being then rinsed in ordinary water. After a short exposure from the glass side (the coated side lying on a black cloth), the plate is flowed over with a solution of one part of gelatine in two parts of water, and dried. It is then coated with the sensitive layer, which I call “ Bild- schicht ” (picture-layer), consisting of Gelatine ... . ... ... 15 parts Sugar ... 14 ,, Distilled water .. 90 „ Bichromate of potash ... ... 3 ,, Glycerine (to every 15 gr. gelatine) 4 drops In this formul, there are objectionable (1) the inter mediate layer introduced between the first and third one, which, not being sensitised, diminishes the adhesion ; (2) the introduction of sugar, which diminishes the resistance of the layer, thus allowing only a limited number of prints. Besides, the concentration seems to me too great. In his “ Photoverrotypy," Lemling recommends several recipes for a first film, consisting of albumen, gelatine, and sugar, and a second layer of chromated gelatine, wherein the proportion between gelatine and bichromate may be called a correct one, but which, owing to its concentra tion, is inclined to a granular texture. But nowhere do we find a hint as to the quality of the gelatine to be selected, nor as to the temperature, which are both of the highest importance. Professor Husnik, of Prague, was kind enough to give me the following description of his method. For the first film prepare a mixture of White of egg 8 parts Silicate of soda 5 „ Water 7 „ After having been well mixed, they are filtered through gauze. With this mixture matt polished glass plates are coated and exposed to the atmosphere for two days, in order that the silicate may be decomposed by the carbonic acid always contained in the air. There results an inso luble compound, consisting of silicate and albumen, which attains the necessary porosity in being washed under a tap for ten minutes, every trace of soluble albumen with carbonate of soda being thus eliminated. Plates prepared in this way need not be exposed from the glass side, and may be kept for over a year. The second plate is formed of:— Extra fine gelatine 5 parts Bichromate of ammonia ... 1 part Water 80 parts The gelatinous solution is first heated to boiling, and upon this the chromate of ammonia is added ; but if one prefers not to boil, chromalum to the amount of one-twen tieth per cent, of the bichromate ought to be added. The plates to be dried at 35° R. As regards the preliminary preparation with soluble glass, I would say that it is not free from objections in so far as double the quantity of albumen is necessary, as in the method of Albert ; and owing to the fact that the mixture coagulates quickly, it cannot be kept, while a mixture of chromium salt with albumen may be preserved for almost any length of time. Besides, the cleansing of the plates is somewhat troublesome. Immersion in alka line solutions is not sufficient, they must be polished with emery, which involves loss of labour and time. And as regards the formul for the second (picture) layer, I find the solution for one coating almost too thin, and the boil ing superfluous. Probably it is the purpose of this latter process to form chromate of oxide of chromium. Some of i 1 1 I I 1 1 1 1 1 1 1 1 I 8 c I t t c c C a I 1 (