Besides its great value to the autotype, Woodburytype, and mechanical
printers as an agent for hardening the gelatine films, it has been
recommended for all sorts of ailments photographic. The silver printer
adds a small portion to his sensitizing bath to keep it in working
order, and to prevent blistering of the albumen; then, again, silver
prints are soaked in a dilute solution of alum, having for its object
the thorough elimination of the last traces of the fixing salt. A very
good proportion to use for this latter purpose is four fluid ounces of a
saturated solution, diluted with one gallon of water, the prints being
well agitated during an immersion of ten minutes.
Of all the uses to which alum is put, perhaps not in any single instance
can so much satisfaction be derived as when it is used to
arrest frilling of gelatine plates. This it has the power to do
instantaneously, and many of the most careful workers, both amateur and
professional, or at least those who do net care to run any unnecessary
risks with negatives which have cost them a good deal of anxiety and
trouble to secure, but prefer to make assurance doubly sure--such
individuals may be numbered by the hundred--make it a point in every-day
practice to immerse all their plates in a solution of alum, either
before fixing, or immediately afterward.
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