"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 | " |
| Water | 240 | parts. |
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. |
| Citric acid | 1 | part. |
| Water | 140 | 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.