Quote Originally Posted by pdeeh View Post
However I have subsequently found a comment (can't find it again now), by none other an expert than PE, to the effect that Ascorbic acid can be temperamental in developers. Or at least that is how what I understood him to be saying.
Ascorbic Acid can be quite temperamental, but in the opposite direction: sudden death of developer, i.e. a jump from almost normal development to none at all in a very short time frame and for no apparent reason. Kodak did find solutions to this issue (DTPA, HEDP), and a a result Xtol working solution lasts for several months, but most home brew recipes don't include a suitable sequestering agent and therefore lack stability. But this issue doesn't seem to happen here in your case.

When I mixed my own experimental developers, I did notice that developer fog doesn't come in small doses: either your negs are more or less fog free, or fog jumps in your face. As a result, even small deviations from the correct recipe can cause high fog levels which make your negs barely printable.

Here is what I would do in your situation:
  • Do yourself a favor and get a pH meter. These are dirt cheap and can be gotten from many sources. pH strips are nice for getting into the ball park, but a pH meter gives you real numbers down to 0.1 or 0.2 pH, depending on what you spend.
  • Until that pH meter arrives, add more and more Borax or Boric Acid to that dev and test with unexposed film clips until you no longer get fog.