It's also been written about quite a bit on the conservators/archives list run off CoOL. One or two of the researchers at the Image Permanence Institute belong to that list and have posted about this...it's also written up in an issue of the Abbey Newsletter--from the early 1990s, in an article that deals with microfilm deterioration. I would post a link to it, but it's all copywritten material--at any rate, if you go to Conservation OnLine and search the Conservation DistList or do a general search of the site, you can probably find similar articles. I think it's more complicated than just having some residual fix left in the material--my understanding from reading this stuff was that Kodak and some of the other manufacturers realized this going back 30-40 yrs ago, but couldn't come up with a quantifiable measure for how much should be retained. Douglas Nishimura (hope I spelled that right) from the IPI has written the most about this on the DistList. You can search by the year or the author.
hope this helps, KT