It is not necessary that the picture should be developed immediately after exposure in the camera; any time that is convenient to the operator may intervene between the processes, provided the aggregate time before and after exposure does not exceed the limits of keeping power of the plate.
The development of the picture may be conducted in two ways, either by immersing the plate in baths or dishes, or by placing it on the levelling stand and treating it with the solutions, in their proper order, as detailed below. Each plan possesses certain advantages, but it is of little consequence which one is followed. Perhaps there is less danger of the film washing off if the plate be treated on the levelling stand, and on the other side with large plates it is more difficult to cover them evenly with the developing solution than it is simply to immerse them in a pan of solution. We say to the reader, try both ways, and make your own selection.
The plate upon being removed from the camera is placed face upwards in a porcelain or glass dish of a convenient size (not too large), and sufficient distilled water is to be poured over it to cover the surface thoroughly—this is for the purpose of softening the preservative solution, and must be allowed to remain on the plate for five minutes; the plate is then to be lifted in and out of the water by means of the silver hook. This done, remove the plate to a perfectly clean dish, and pour carefully over it the developing solution, composed of
| Saturated Solution of Gallic Acid ([p. 10]) | 8 | ounces. |
| Solution of Nitrate of Silver ([p. 10]) | 2 | drams. |
| THOROUGHLY MIXED. | ||
In a few minutes the picture will begin to make its appearance, and will gradually unfold its details under the influence of the developer, until the whole of them are apparent; on raising the plate, however, when this stage of development is reached, and viewing it by transmitted light, the picture will appear weak and poor; we must now remove the plate from the bath, and add 2 drams more of the nitrate silver solution, and having thoroughly mixed it with the gallic acid already in the dish, we return the partially developed plate, which in the course of a few minutes will have acquired a great amount of intensity,—the exact degree can be regulated by the time of immersion: when the picture appears sufficiently intense, it is to be removed from the developing dish, and a gentle stream of water is poured over it, in order to remove any adhering developing solution, and stop all further reducing action on it.
During the whole time of the development, the gallic acid should remain quite clear; it will become slightly discoloured before the end of the development, but it ought not at any time to become muddy, or it will deposit a sort of sandy sediment on the surface of the plate, which cannot be removed by subsequent washing.
The usual time occupied in the development of a successful picture is from 20 to 30 minutes, it might be developed much quicker by using pyrogallic acid, but at present I give the preference to the developer I have described, as I believe it to be more certain, and more under the control of the operator than the pyrogallic acid; and further, as it is not necessary to watch the development all the time it is going on, there can be very little saving of time in the more rapid method of bringing out the latent picture.
The picture being washed free from the adhering developing solution, is to be placed on the levelling stand, and subjected to the seventh part of the process—