This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
The Use Of Two Trays For Developing. In case of uncertain exposure, whether over or under-timed, and even for properly timed plates, a good method to adopt is to use two trays for developing. The reason for this is that should you find a plate over-exposed you can immediately transfer it to the tray which contains the old developer. Use one tray for normal developer, starting all plates in this. In the other pour the old developer previously used, decanting clear solution. By clear solution we mean, not a solution that is clear in color, but simply clear of particles of dirt, or film, which might have come from the plates that were previously developed. Having placed the plate in a normal developer, watch it very closely and when the image begins to appear examine the plate and note the parts which should appear first. The parts which will naturally appear first will be the highlights, or the whitest parts of the image. Note if the shadows are holding their relative value to these highlights.
Developing Different Brands Of Plates. By relative value we mean the natural gradation from the highlights to the deepest shadows, taking, of course, into consideration that different brands of plates develop differently. For instance, with Cramer plates the entire image, both highlights and shadows, will appear, if not over-exposed, at about the same time; that is the highlights will be closely followed by the shadows. However, each light and shadow will appear in their proper tone and will grow stronger as the plate continues developing. When developing this brand of plate with correct exposure, you pay little attention to the shadows, so long as they remain clear, but develop entirely for the highlights in order to obtain their proper strength. When they are fully developed the shadows will also be developed.
199. In case, however, of over-exposure on Cramer plates, the shadows will flash up quickly, and be quite hazy. They will have a foggy appearance, there will be a lack of distinction between highlights and shadows. The entire plate will appear fogged, the amount of fog ranging according to the over-exposure. If only slightly over-timed, the fog visible will be only slight. If very much over-timed the fog will not appear greater but much earlier (quicker). In - either case, place the plate immediately into the tray containing the old developer and allow it to remain there until the fog is checked and the plate is sufficiently restrained, always rocking the tray to keep the developer moving.
200. With almost all other brands of plates the highlights appear some little time before the shadows. Even if overtimed, the highlights will appear first, then the middle tones and finally the shadows, but if over-timed the shadows will soon begin to fog over. As soon as they show signs of fog, indicating over-exposure, they should be restrained at once by placing them in the old developer. When developing any brand of plate bear this in mind, because, should the image flash up quickly, the shadows appearing at almost the same time as the highlights, you will know the plate is over-timed and you should immediately transfer it to the tray which contains old developer.. If the plate seems quite hazy, indicating very much over-exposure, then add to the old developer, a few drops of ten per cent, solution of bromide of potassium, a stock solution which should be kept on hand at all times.
201. Preparing a Ten per Cent. Solution of Bromide.- To prepare this stock solution in a twelve-ounce bottle dissolve one ounce of bromide potassium in ten ounces of water, which, when dissolved, will give you practically a ten per cent, solution. The old developer, and additional bromide acting as a restrainer, checks the further development of the shadows, and permits the developing agent (pyro), to build the highlights to their proper density.