How long does it take for Rodinal efficiency to "expire"? I have used R09 1+100 for like 20 rolls, but I realized that my rolls are underdevelopped since a few months. I first thought it was an issue with my scanner and almost forgot to look at the actual negatives, silly me.
I don't understand the exact issue. I use the same dilutions as before, same timings, same process, same films, but the results are not satisfactory anymore. I wonder whether this could be my R09 being too old or badly conserved, or perhaps something else, see below.
The dilution I use is 4+400 when I develop only one 135 roll, or 7+700 when developping two rolls or a 120 roll, so that it can be fully immersed. Stoechiometrically-speaking, it means that when I develop two 135 rolls, they have less developper available per unit of surface, as compared to a single 135 roll or a single 120 roll (approximately the same total area of film). And indeed, the last two 135 rolls I got underdevelopped where developped together in the same process, while a few weeks before I developped a 120 film and it came out quite normal. Should I just increase the dilution to 8+700 when I develop two 135 rolls (I can't pour 800 mL in my canister)? More than that, and forget the 1+100? Should I avoid double rolls in stand dev*?
* : I did open the canister in the black at 30 min to put the bottom roll on top and vice versa, to avoid discrepancies.