Did you have problems with the anti-halation layer clearing?
Yes, but not just a failure to clear. There appears to be a gelatin layer on the backside of film -- perhaps to hold the anti-halation layer on and perhaps to help keep the film from curling towards the heavier gelatin layer on the other side.
My guess is that the hardening fix hardened that gelatin layer and would not allow it to release all the chemicals making up the anti-halation layer. What was left was patchy chemical residue-looking junk on the back. JLP -- I believe any non-hardening fix would suffice, but please feel free to maintain your anti-Ilford bias. Kodak does (or in many cases, did) make quality products.
Perhaps it is because the back of the film is against the wall of the drum and it takes longer to get rid of the layer than with any other development method. Thus the hardener would do its thing before all the components of the hardening layer could be removed. I have not had this problem developing FP4+ in trays and using hardening fixers.
Long washes would not remove the chemical deposits on the back, though soaking in a tray of fixer after removing the film from the drum did help reduce it. I suppose I could take a few of those negatives and experiment -- try acid baths, alkaline baths (to soften the gelatin), steel wool pads
, or whatever it takes to clean them up. I have some nice 8x10 negs that I can not use.But FP4+ is a good film. HP5+ is a different beast altogether!
Vaughn
Kodak copy film was quite unlady-like and rather fun to dance with.