Quote Originally Posted by ajseier View Post
Silly me, I forgot about pH. That being said however, why does a fixer pH difference cause color shift? I've heard of that happening with developer, but not with fixer.
You mix up two separate effects that can change colors:
  1. If the three layers are developed at incorrect rates (incorrect pH will do that to you), layer density is not in lock step and colors will be off. Note that because of this even the E6 FD, which technically is a strong b&w developer, can have impact on slide colors.
  2. Dyes change their color hue depending on whether they are protonized or not, and different pH changes the degree of protonization. Indicator dyes are examples where this is particularly pronounced, but I hear that most dyes show this effect. Since fixer is the last bath that has significant concentration (hence buffering), its pH seems to be quite important.