This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
One of the most extensive establishments for the purpose is that of Messrs. Winter, in Vienna. They say to photographers in general: If you will send us a portrait, either negative or positive, we will produce you an enlargement on canvas worked up in monochrome. The success of their undertaking lies in the circumstance that they do not produce colored work - or, at any rate, it is exceptional on their part to do so - but devote their efforts to the production of an artistic portrait in brown or sepia. In this way they can make full use of the dark brown photograph itself; there is less necessity for tampering with the enlarged image, and natural blemishes in the model itself maybe softened and modified, without interfering much with the true lines of face and features. The monotone enlargements of Messrs. Winter, again, exquisitely as most of them are finished, do not appear to provoke the opposition of the painter; they do not cross his path, and hence he is more willing to do them justice. Many a would-be purchaser has been frightened out of his intention to buy an enlargement by the scornful utterance of an artist friend about "painted photographs," and in these days of cheap club portraits there is certainly much risk of good work falling into disrepute. But a well-finished portrait in monotone disarms the painter, and he is willing to concede that the picture has merit.
"We cannot use English canvas, or 'shirting,' as you call it," said one of our hosts; "it seems to contain so much fatty matter." The German material, on the other hand, would appear to be fit for photography as soon as it had been thoroughly worked in hot water and rinsed. Here, in this apartment, paved with red brick, we see several pieces of canvas drying. It is a large room, very clean, here and there a washing trough, and in one corner two or three large horizontal baths. The appearance is that of a wash-house, except that all the assistants are men, and not washerwomen; there is plenty of water everywhere, and the floor is well drained to allow of its running off. We are to be favored with a sight of the whole process, and this is the first operation.
Into one of the horizontal baths, measuring about 5 by 4 feet, is put the salting solution. It is a bath that can be rocked, or inclined in any direction, for its center rests upon a ball-and-socket joint. It is of papier mâché, the inside covered with white enamel. Formerly, only bromine salts were employed, but now the following formula is adopted:
|Bromide of potassium||3||parts.|
|Iodide of potassium||1||part.|
|Bromide of cadmium||1||"|
Four assistants are required in the operation, and the same number when it comes to sensitizing and developing, all of which processes are commenced in the same way. The bath is tilted so that the liquid collects at one end, and near this end two assistants hold across the bath a stout glass rod; then the canvas is dipped into the liquid, and drawn out by two other assistants over the glass rod. In this way the canvas is thoroughly saturated, and, at the same time, drained of superfluous liquid.
The canvas is hung up to dry; but as sometime must elapse before this particular piece will be ready for sensitizing, we proceed with another canvas which is fit and proper for that process. The room, we should have mentioned, is provided with windows of yellow glass; but as there is plenty of light nevertheless, the fact hardly strikes one on entering. The sensitizing, with a solution of nitrate of silver, is conducted with a glass rod in the same way as before, the solution being thus compounded:
|Nitrate of silver||4||parts.|
Again the canvas is dried, and then comes its exposure.
This is done in a room adjoining. We lift a curtain and enter a space that reminds one of the underground regions of a theater. There are curtained partitions and wooden structures on every hand; dark murky corners combined with brilliant illumination. Messrs. Winter use the electric light for enlarging, a lamp of Siemens' driven by a six-horse power engine. The lamp is outside the enlarging room, and three large lenses, or condensers, on three sides of the light, permit the making of three enlargements at one end at the same time. (See Fig.)
The condenser collects the rays, and these shine into a camera arrangement in which the small negative is contained. The enlarged image is then projected, magic lantern fashion, upon the screen, to which is fastened the sensitized canvas. The screen in question is upon a tramway - there are three tramways and three screens in all, as shown in our sketch - and for this reason it is easy to advance and retire the canvas, for the purpose of properly focusing it.
Even with the electric light now employed, it is necessary to expose a considerable time to secure a vigorous impression. From ten minutes to half an hour is the usual period, determined by the assistant, whose experienced eye is the only guide. We should estimate the distance of the cameras from the enlarging apparatus to be about fourteen or fifteen feet in the instance we saw, and when the canvas was taken down, a distinct outline of the image was visible on its surface.
By the way, we ought to mention that the canvas is in a decidedly limp state during these operations. It has just sufficient stiffness to keep smooth on the screen, and that is all; the treatment it has received appears to have imparted no increase of substance to it. Again it is brought into the red-brick washing apartment, and again treated in one of the white enameled baths as before. This time it is the developer that is contained in the bath, and the small limp tablecloth - for that is what it looks like - after being drawn over the glass rod, is put back into the bath, and the developing solution rocked to and fro over it. The whiteness of the bath lining assists one in forming a judgment of the image as it now gradually develops and grows stronger. Here is the formula of the developer:
The developer - which, it will be noted, is very acid - is warmed before it is used, say to a temperature of 30° to 40° C.; nevertheless, the development does not proceed very quickly. As we watched, exactly eight minutes elapsed before Mr. Winter cried out sharply, "That will do." Immediately one of the assistants seizes the wet canvas, crumples it up without more ado, as if it were dirty linen, and takes it off to a wooden washing trough, where it is kneaded and washed in true washerwoman fashion. Water in plenty is sluiced over it, and after more vigorous manipulation still, it is passed from trough to trough until deemed sufficiently free from soluble salts to tone. The toning - done in the ordinary way with gold - removes any unpleasant redness the picture possesses, and then follows the fixing operation in hyposulphite. As canvas is more permeable than paper, these two last processes are quickly got through.
The final washing of the canvas is very thorough. Again it is treated with all the vigor with which a good laundry-maid attacks dirty linen, the canvas, in the end, being consigned to a regular washing-machine, in which it is systematically worked for some time.
When the canvas picture at last is finished, it presents a very rough appearance, by reason of the tiny fibers that stand erect all over the surface. To lay these, and also to improve the surface generally, the canvas is waxed, the fabric is stretched, and a semi-fluid mass rubbed into it, heat being used in the process, which not only gives brilliancy, but seems also to impart transparency to the shadows of the picture. The result is a pleasant finish, without vulgar glare or glaze, the high lights remaining beautifully pure and white.
Of course, the price of these canvas enlargements varies with the amount of artistic work subsequently put upon them; but the usual charge made by Messrs. Winter for a well-finished life-size portrait, three quarter length, is sixty florins, or about £5 sterling as the exchange now stands. Besides working for photographers, Messrs. Winter are reproducing a large number of classic paintings and cartoons by photography on canvas in this way (some of them almost absolutely untouched), and these, as may be supposed, are finding a very large sale among dealers. Such copies must necessarily be of considerable value to artists and collectors, and altogether it would seem that Messrs. Winter have hit upon a novel undertaking, which bids fair to make them a handsome return for the outlay (large as it undoubtedly has been) made upon their Vienna establishment. - Photo. News.