As in the case of tinting, the nature of the tone obtained with the
various solutions depends on the following factors:
a. _The nature and dilution of the toning solutions._ Except in those
cases where it is recommended to revive the bath by adding more
acid, it is not advisable to modify the composition or dilution of
the various solutions, as these have been adjusted to give the best
results.
b. _Temperature of toning._
In most cases a change of temperature from 60 to 70 degrees F. has
merely the effect of changing the time of toning. It is advisable,
however, to maintain the temperature of the various solutions between
65 degrees and 70 degrees F.
c. _Time of toning._
Except in the case of tones F and G when toning proceeds to a limit,
the nature of the tone produced varies with the time of toning,
reaching a limit in from 10 to 15 minutes, so that in a shorter time
intermediate tones are produced. Since most of the toning processes
intensify the original image, if an intermediate tone is required, it
is usually necessary to commence toning with denser film than when
toning is to be carried to the limit. See tones B, C and D.
When producing intermediate tones, it is therefore possible either to
tone in the normal bath for a given time or in a diluted bath for a
longer time. In order to reduce the number of individual toning baths
to a minimum it is recommended to vary the time of toning rather than
to vary the dilution of the bath and to judge the tone by inspection.
Since the strength of the toning bath falls off with use, inspection
is necessary in all cases except Tones F and G.
Before commencing work with any bath, it is advisable to make a test
on a short length of film.