I had a similar issue with Delta 100 when I switched from tray to a unicolor roller. TMX 100 did not have the issue. I cured it by dropping the fixed film in double strength hypo clear. I have no idea why that fixed it,
I ran what I thought was ruined Delta 100 through the hypo clear for five minutes and fixed those too.
Maybe TMX and Delta have different types of anti-halation layers.
Sorry to resurrect an old thread, but I'm currently facing an issue that seems to be similar to the one discussed here.
Since switching from Kodak TMAX100 to Ilford Delta 100 about two years ago, I've noticed occasional, random crack marks on my processed 4x5 film. The marks are quite irregular (not straight lines) and never inside the image area of the negative (always in the margins). I presumed maybe Ilford film is a bit more delicate than Kodak, and I wasn't being 100% careful somewhere. But frankly, the crack marks didn't affect the printed image, so I didn't pay much attention to it. Until the other day...
While I was hanging up my latest batch of negs to dry, I accidentally rubbed one of these crack marks with my finger. To my great surprise, it wasn't a crack at all as I had always thought, but some kind of plastic/film-like substance that easily peeled off (much like the protective film for an LCD screen during shipment). Furthermore, the substance is on the base side, not the emulsion side.
After reading this thread, I soaked the negs in water again and attempted a 5-minute hypo clear bath, followed by thoroughly re-washing the negatives. But that has no effect on removing this filmy substance. I'm curious if this is the same issue others were discussing in this thread, and if so, whether there is a confirmed solution. I've tried contacting Ilford Photo, but so far not received any reply.
For reference, I don't do a pre-soak. My negatives have always been developed in BTZS tubes using fresh developer (DDX 1+7), fresh stop bath, fresh rapid fixer, and thorough washing with a final dip in distilled water + PhotoFlo. I've never used hypo on negatives before, but tried it this one time because it was mentioned above.
I've uploaded a video showing the film-like substance being peeled away from the base side
here
Any help or insight would be most appreciated!!