After tonight's vastly more precise attempt I'm beginning to believe you too. Times were almost second perfect and temps were as bang on as you can get. Also using this sheet of Portra instead of cheap supermarket Superia eliminates the out of date film issue too. Process of elimination points to a chemical issue, to which my mixing the parts before adding the water, as odd as it seems to someone with pretty minimal knowledge of chemicals in general, could very well be the culprit.
Originally Posted by AlexG
I'll be sure to try and build up the courage to run another fresh, properly mixed batch of chems in the next couple of days.