emulsion and base of the film simultaneously. The schematic, fig 1-8b, shows
the relation of the film to the air plenums in the drying compartment of a
continuous processor.
(1) Air is heated to temperatures ranging between 100F and 150F (37.8
to 65C) and is directed against the film at velocities of from 5000 to 6000
feet per minute.
An efficient squeegee must be used since surface liquid
remaining on the film will result in non-uniform drying.
(2) As with any other type of dryer, the condition of temperature and
velocity must be adjusted to the local climate. Otherwise, the film will dry
more rapidly at the edges causing drying marks.
(3) Some types of film tend to become excessively brittle when dried
rapidly by this method. This is due to reduced relative humidity rather than
overdrying.
Figure 1-8b.
Impingement dryer
Figure 1-8a.
Parallel-flow dryer
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