I've had a similar problem before with tray development, but I've since moved an hour away and switched to tank development. Tank development seemed to fix the problem for the past >100 negatives using D-76, but I never solved the tray development issue.
Recently my skies have become uneven again. It seems to be strongly correlated with when I switched to Adonal developer. I'm mixing the developer for about 10 seconds before beginning, then my process has been:
- developer → 1:50 ratio, 14min, 20C, 4 inversions once a minute
- stop bath (water) → 1min
- fixer (fresh) → 4min
- wash → 4 cycles (starting fresh each cycle), rotating 5x, 10x, 20x, 40x
photoflo → 30sec
Film: Ilford Delta 100 4x5
- Tank: SP-445
What could be causing this uneven development?