The keeping
qualities of photographic chemicals to a degree is dependent on
the dilution of the mix. In the first instance you should always
follow the manufactures recommendation when mixing stock solutions by
only adding the chemical to that quantity of water thus giving you a
known starting point. If you require a more dilute working developer
you should only make this up just before you are about to use it.
Once used it should be discarded.
Reusable
developers are poured back into their containers when finished with.
Each time you pour it back a little bit is used up, it is a good idea
to keep these containers full to stop the developer going off. This
can be achieved in several ways if it is a plastic bottle you can
squeeze the air out just before you nip the cap up, add glass marbles
to the bottle so increasing its level, use a concertina bottle or the
plastic bag out of a wine box ( if using one of these make sure it
has been thoroughly cleaned.)
Remember that
developer that has been used is likely to go off more quickly. It is
a good idea to keep a record on each bottle of how many film or
prints and what format has been developed. When you think you have
reached the maximum usage discard it and make a fresh batch.
