We now proceed to spoon out 3 grains of pyrogallic acid into the developing cup. The first time or two we take the trouble to weigh out that quantity, but afterwards we can easily guess the amount by its bulk. Adding to this 2 ounces of water, we see that the pyro. quickly dissolves. Now add 4 drops of solution A, and the developer is ready. This amount of developer is quite sufficient for a 5 X 4. plate, particularly if the developing dish be of flat vulcanite, and of a size suitable to the plate developed. Of course if a large dish be used for a small plate, more developer must be needed to cover that plate. And the plate must be covered too, or stains are likely to result.
Taking the exposed plate from its double back, and keeping it at a safe distance from the red light, we place it in its dish, film side upwards, and immediately empty upon it the contents of the developing cup. This must be done in such a way that the liquid flows over the glass plate in one even wave. We may now put the cup aside and watch the gradual growth of the photographic image on the gelatine plate. This is always a pleasant, and most interesting sight. The plate when first wetted has a cream-colored surface, although it looks red enough under the light with which we are now working. No change occurs at once, but presently we see that part of the plate is rapidly darkening, while the extreme edges - which have been protected in the camera by the rebate of the dark slide - remain white as before. The darkening goes on, and now we see that the foliage of the trees - quite white - is projected upon the blackness. We recognize the dark part of the picture as the sky. It is the brightest thing in the landscape, and therefore it has had the greatest effect upon the sensitive surface in the camera, blackening a portion of that surface to a greater extent than could the light rays from any other part of the composition. But the picture is not only black and white : for now we find that silvery half-tones are making their appearance. These are found on the markings of the tree trunks, the various shades on a lichen-covered stone wall, and other objects. Still watching the gradual development of the picture, the action seems to hang fire a little. Now is the time to look to our accelerator (A solution) for further help. But we must not pour any direct into the dish, or it would have undue action on one part of the plate, and the negative would probably be spoilt. We therefore drop into the developing cup 6 drops of the solution, or thereabouts; empty the developer upon it, and immediately return the whole of the mixture to the dish. The effect upon the picture is rapid. It quickly gains in strength, and unless care be taken the picture may be made too dense by allowing the action to go too far. The exact time when the developing process should be stopped, can only be learnt by experience. The beginner can, however, judge of the amount of density on the plate, by taking it out of the dish and holding it close to the ruby light so as to look through it. If indiarubber thumb and finger stalls be used, this can be done without soiling the hands. (It may be observed here that after the development has commenced, the plate is not nearly so sensitive to light as it was before. After, therefore, the image has once begun to peep out, development may be. continued under quite a bright light, provided that it is of an orange colour)
When it is judged that development is complete, and when complete there should be very few white places discernible upon the plate, the contents of the dish are emptied into the sink, and the negative is well flushed with water. Plenty of water at this stage, means a good clear negative. After this the plate is put into the alum dish for about 2 minutes, then it is ready for the fixing operation in the hypo: dish.
Let us for a moment pause to see what this process of fixation means. The plate originally consisted of a film of bromide of silver mixed with gelatine. Only a portion of this bromide has been utilized in making our negative, and by the action of the light in the camera, and subsequent development, this portion has been darkened. But by far the larger mass of the film remains as unaltered bromide of silver; and by examining the back of the developed plate, we can see the cream-coloured film almost untouched by the chemicals we have been using. This unaltered bromide causes the plate not only to be opaque, but if allowed to remain, would be infallibly darkened by light in the course of a short time. So we must get rid of this bromide of silver; and the best way of doing so is to dissolve it out of the film with hyposulphite of soda. We now see why this chemical is called the fixing salt, and why it is so prejudicial to the other photographic chemicals, except in its own proper place. Before putting the plate in the fixing bath it should be well rinsed under the tap.
Under the action of the hypo, the plate gradually loses its opacity, and becomes darker in appearance. It should be left in the fixing bath for a few minutes after the last trace of whiteness (bromide of silver) has disappeared. It is then thoroughly washed under the tap, placed in a bath of clean water (which should be changed at intervals) for two or three hours, dried in a plate rack and the negative is finished.