The DARKROOM COOKBOOK, Third Edition

Printing Out Processes
You must always believe that there is fertile soil for your ideas. If you lose hope then
you will miss opportunities to plant a seed.
—Ruth Bernhard
The term “printing out paper” and the associated initials P.OP. were introduced in 1891 by
the Ilford Company for their gelatin-chloride papers. The term has since been applied to any
paper that requires ultraviolet light to form a complete image without the need for chemical
development. In particular, it is used when referring to salted paper and related processes.
The use of P.O.P. is a time-honored method for making inexpensive prints without a darkroom.
The printing technique is simple: the coated paper is contact-printed with a negative
using the sun for a light source to make a visible image without development (a UV lamp,
available from grocery and hardware stores, can also be used).
There are several different types of P.O.P., salted paper, albumen, gelatino-chloride, and
collodio-chloride, differing in the medium used to suspend the light-sensitive substance and if
the sensitizer is applied in the salting solution (as in an emulsion) or as a second step. In the
traditional salted paper process the silver is held by the fi bers of the paper while albumen
papers use egg whites as the binder. Gelatino-chloride papers suspend the silver in a gelatin
layer and collodio-chloride uses a binder of cellulose nitrate.
The basic light-sensitive substance used in all of these papers is silver chloride with an
excess of silver nitrate. Once the image has been printed and toned, it is fi xed, washed, dried,
and preserved in much the same way as a silver print. Because the silver particles of printed
out images are a much fi ner size than those of developed out prints, they are often more susceptible
to deterioration. But with proper processing, they will stand the test of time as well
as any process. Indeed, collodio-chloride is actually the most stable silver printing process
because the nitrocellulose binder hermetically seals the silver from the harmful atmosphere
that fades all silver base photographic prints.
Printing out papers can only be contact-printed. For this reason a 4 � 5 inch or larger
negative is usually preferred. Printing-out papers rely on a technique called self-masking. This
means that thin areas of the negative allow the light to quickly darken the paper and block
light from reaching the lower layers of the sensitive surface. The result is that the shadow
areas are held back slightly allowing the highlights of the picture to print. A good print for
these papers requires a dense negative with good shadow detail and clear base in the deepest
shadows.
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