van Monckhoven, Désiré van. A Popular Treatise on Photography. Translated By W.H. Thornthwaite. London, 1863.

Chapter V.
On the Dark Room, and Photographic Laboratory

IN the practice of photography, three different rooms are necessary: one well lighted, in which the sitter is placed another of commodious dimensions, which serves he purpose of a laboratory; and a third made quite dark, ire which are performed all those operations which may not see the light of day.

The laboratory should be of such dimensions as are to meet the wants of the photographer. Amateurs generally take plenty of room, because in most cases it. costs them nothing; but professional photographers are oftener obliged to content themselves with a small apartment, which frequently serves the double purpose of dark room and laboratory.

However this may be, it is best to have a large preparations can be made, positive proofs printed, &c., on the ground floor, well furnished with drawer and tables.

The dark chamber ought to be, on the contrary, very simple Two or three tables are sufficient, and the light should either be entirely excluded by pasting black paper over the windows, and the operations conducted by the light of a candle or a gas jet, surrounded by a square lantern of yellow glass, or else, as often preferred, the dark room is so arranged that the light comes exclusively through a frame of yellow glass about 10 inches by 8 inches, and this covered with a sheet of very thin white paper, in order to impede the passage of the direct solar rays. A hinged frame is fitted in front of this square of yellow glass in such a way as to admit of its being totally or partially covered, in order to diminish or increase the amount of illumination at pleasure.

Fig. 28. Dark Chamber.

It is necessary to select glass of a deep yellow colour, and avoid the paler kinds.

The drawing (Fig. 28) represents the dark chamber which has been used for many years by M. Monkhoven.

The entrance is at the bottom of the room, and the door, for greater security, covered with a black drapery. A cistern of water, furnished with a tap, supplies the necessary means for washing, and underneath this is

placed the sink, with a pipe to convey the waste water outside. On one side should be placed the dishes us for nitrate of silver bath, and for sensitising albumenised paper, and on the other those which appertain to fixing and other operations incompatible with the nitrate silver solution. Shelves should also be fitted up support funnels while filtering, bottles, &c.

A second reference to Fig. 28 will show the arrangement by which the amount of light is regulated; it w: be seen, in fact, that by lowering the yellow frame, which is shown in that position in the drawing, the room inundated with light. This frame need closed only when the plate is immersed in the nitrate of silver bath, and during the development of the image, When the required intensity has been attained in the c last operation, the plate is washed and the frame lowered in order to see more clearly. If the sun shines on this it is absolutely necessary to paste over it sonic. thin paper to stop the too direct rays.