The soda acetate toning bath still holds its own against the many formulae for toning that have from time to time been published; and deservedly so, as by its use the utmost range of tone can be secured at will, and if the silver be carefully washed out of the prints previous to toning, the acetate bath will keep in order for a considerable length of time, improving in quality with age, if properly strengthened, and not overworked.
Gold chloride...... 1 gr.
Soda acetate .. .. .. 30 gr.
Water ........ 10 oz.
Another method, of great ease in preparation and uniformity of action, is given by Werge.
Washing the print after fixing is a very important factor in securing lasting prints, and always receives a deal of attention from the careful photographer.
Constant changes of clean water for 2-3 hours will more effectually cleanse the prints than 12 hours' soaking. A very delicate and ready test for the elimination of soda is given thus by Abney: -
Potassium permanganate 2 gr. Potassium carbonate .. 20 gr. Water ........ 1 qt.
The addition of a few drops of this rose-coloured solution to a pint of water will yield a slightly pink tinge. If there be any trace of hyposulphite present, this will give place to one of a greenish hue.
In the production of photographic transparencies, the great difficulty has always been to obtain with certainty a thoroughly satisfactory colour. For uniformity in the matter of colour, no method can excel the carbon process, but for some reason amateurs seem to avoid it. The colour generally admitted to be the most pleasing is a dark, rich sepia brown, first produced by Ferrier and Soulier, of Paris, in their exquisite stereoscopic transparencies on albumen. As lantern slides from photographic negatives are becoming popular, a brief account is given of this method of production, which is unequalled for brilliancy, sharpness, beauty of colour, and certainty of result, while it is surely the most economical of processes. It further has the advantage that the development of the plate can be conducted in a bright yellow light.
Separate the whites from several eggs, remove the germs, and to every oz. of albumen add 2 gr. potassium iodide; when this is dissolved, the mixture must be beaten to a stiff froth, and put aside for several hours to settle; the fluid should then be decanted into a clean glass vessel. If bright and clear, it is fit for use; but if any particles are seen floating about, the albumen must be filtered. To accomplish this, a tuft of wet cotton-wool is pressed evenly into the neck of a glass funnel, and the albumen is poured gently on. It should run through quite clear; if not, the operation must be repeated.