20
degrees centigrade is the standard temperature
that film development should be carried out at. It is also important
that this temperature be maintained throughout the process. You may
use a higher or lower temperature which will shorten or lengthen the
development time. There is a risk that the negatives may not be fully
developed; you should wherever possible follow the instructions as to
time and temperature unless an alternative has been suggested by
those instructions. With experience you will know what temperature
and time combinations give good results. I personally always develop
my film at 20 degrees C unless a higher or lower temperature is
recommended.