Variations in temperature during the process cycle, they can cause a large effect on apparent graininess. That's why some get poor results and others get superb results.
In Germany many workers use Rodinal at 15-16ºC to get the finest grain and all steps are at that temperature. The problem is Rodinal contains free Hydroxide which softens emulsions and shifts in temperature cause surface artifacts on the gelatin layer of the film. There's no need to use low temperature you just need to be very consitent at all stages of the process +/- 1ºC including washing and you get superb results. It's that simple, deviate and you'll lose everything to excessive apparent graininess and very poor quality, no edge sharpness lower micro contrast etc.
Ian
I would never, ever use a developer that required such strict control of washing temperature. My wash water is often 5 degrees C different from processing temperature and I never find any problems with my film at all. +/- 1 degree C seems ridiculous to the extreme.
Shanghai tap water temperature changes radically depending on the season. I see almost 10 degrees C of variation.
