Sorry for the late inquest... I'm experimenting with the kodak sepia toner and found this link http://www.teachingphoto.com/downloads/Sepia.pdf that says fixing removes any "undeveloped" silver halides that were not "re-developed" in the toning bath. It's my understanding that using a hardening fixer is not a good thing for fiber prints. if this is the reason for fixing, then wouldn't a regular (Ilford Rapid) fixer work just as well? Or is there another alternative. I'm guessing this is used in partial toning? What about Sodium Sulfite?