Lay the paper on a board with a piece of blotting-paper beneath, and apply this mixture copiously to it with a clean Buckle's brush. Hold up the paper to drain for a minute, then blot off the surface moisture with clean blotting paper, and put the sensitive paper into the dark slide.
The .Expouere.—The average time of exposure, with a good light, a lens of fifteen inches focus, and a half-incb stop, is seven minutes.
To develop the Pleture.:--Lay it on a board, and brush over it, with a clean Buckle's brush, a mixture composed of 3 parts of so lution A, and 2 parts of solution B. The picture, the darker parts of which are at first faintly visible, soon comes out of a fiery red tint. At this stage of the development it is necessary to check it, in order to obtain dense blacks instead of feeble reds in the darker parts of the negative. To accomplish this, brush over the picture, and complete the development with a solution of gallic acid alone, Under this treatment the reds soon darken and intensify, and become eventually opaque blacks. The entire development should occupy about twenty minutes. It is an excellent plan, after having brushed on the gallic acid, to lay the paper face downwards on a horizontal glass slab, on which a quantity of gallic acid solution has been previously spread.
To fix the Picture.—When the details are fully out, and the blacks of the proper intensity, wash the negative with water, and then im merse it in a solution containing 1 part of hypo-sulphite of soda to 4 parts of water. Let it remain until the whole of the yellow iodide of silver is removed from the paper. Then wash and soak in water for several hours, changing the water several times, in order to remove the whole of the hypo from the paper. Lastly, hang it
up The to negative is now finished, and may be waxed at any convenient time. See "Waxing," There are one or two important points to be observed in this process :— If the iodized paper is excited with a weak solution of aceto nitrate of silver containing no admixture of gallic acid, it is quite as sensitive, or even more sensitive than before, but the negative is devoid of density, and the dark portions are grey, feeble, and me tallic, like the dark parts of a collodion positive on glass when viewed by transmitted light. This sufficiently shows the importance of introducing organic matter with the exciting solution. But the above effect does not take place equally with all kinds of paper. There is a coarse spongy kind of Whatman's paper, sized perhaps in a peculiar way, in which the gallic acid may be advantageously omitted in the exciting solution. If, on the other hand, too much gallic acid is added to this solution, the paper is liable to become brown all over, particularly in hot weather. The process has there fore its drawbacks and uncertainties, particularly at that season of the year when photographic tourists are most in want of a good process. A good test of the proper stat,e of the sensitive paper, is to take a strip into the light. If it darkens instantly to a cold grey tint, incapable of being intensified by the further action of light, the negatives vvill probably be grey and feeble ; but if it darkens to a redder tint, which gets still darker by continuing the exposure, there is sufficient organic matter present to give a good intense picture.