When the plate has been sufficiently developed, which will be in from three to five minutes, the yellow color will begin to fade, and the outlines, which have been quite sharp, will grow dim. At this point, if one looks at the plate the picture can be quite distinctly seen on the back.
Take the plate from the developer, rinse it thoroughly in clean water, and place it, film side up, in the tray of hypo solution, which is made by dissolving 1 oz. of hyposulphite of soda in 4 oz. of water.
This bath, which is usually called the fixing-bath, though the proper term would be clearing-bath, removes from the negative the sensitive silver salts which have not been affected by light or by development, and makes the image permanent. After the plate has remained in the clearing-bath for five minutes it will be found on looking at the back of the plate that the yellow color has almost entirely disappeared, leaving on the glass the clear image of the landscape. The plate should remain in the hypo for ten minutes, so that the salts of silver may be thoroughly dissolved, or the plates will look streaked, and will not make satisfactory prints.
The plate must next be washed to remove all traces of hypo. Hypo stains the negative, and if not thoroughly washed out is apt to form again in crystals and ruin the negative.
An hour is long enough to wash the negative in running water, and two hours, with four or five changes of water, where there is no running water. When the negative has been washed long enough, take a small wad of soft cotton, and holding both plate and cotton in the water wipe the film gently with the cotton to remove any dirt which may have settled in the film. If one has no drying-rack set the plate on a shelf, with the film side toward the wall to avoid the settling of dust in the film.
When the negative is dry, place it in an envelope, number and mark it, and place it in some place where it may be found without trouble.