The drying room, or box, as the case may be, must be kept cool, and
if any current of air is induced it should be cool and constant, so
that the drying may proceed with perfect regularity until the
process is complete. Should the drying by any means be checked a
line will be formed on the plate, showing where the drying stopped
for the time.
Plates may be dried by a current of warm air, but [p048] they are
much more likely to frill during development; and a very little heat
will melt the coating.
If the plates are dried by an induced current of air, the process
may be hastened by placing dishes, filled with chloride of calcium,
in the air passage to the drying box or room. The chloride will
absorb all the moisture from the air passing over it, and the dry
air will take up the moisture from the plates.
When the chloride of calcium becomes too damp for further use, place
the dishes containing it in an oven and drive off the moisture by
heat, when the dry calcium may be again used. By employing such
means the plates may be dried in a few hours.
After the plates have become dry, they should be packed in good
light-tight boxes and kept in a dry room until wanted for use.