Hi J.L. I also picked up a copy of that very interesting book. I am glad to have it, but wish that the authors had backed up and/or explained many of their statements further. I looked up one of the references, specifically "New Procedures for Processing and Storage of Kodak Spectroscopic Plates, Type IIIa-J", Journal of Imaging Technology (SPSE; now IS&T), Feb. '84. I would never have interpreted this paper to say what they have, so presumably their statements are based on the other reference ("Haist", whatever it is). PS, is the "most current research" really 1984 or earlier?(posted 9029 days ago)Not to bore you, but the paper essentially reports use of an accelerated aging test (elevated temp in an oxidizing atmosphere) to produce "microspots" (oxidized, etc, silver) in the type IIIa-J plates. The microspots were similar to those first reported at a conference in 1980. Finally, various process variations were tested and "aged". Two variations compared Kodak F-5 fix (6min + 6min) vs Rapid Fix (4 min) where the Rapid Fix seemed slightly more resistant to microspot formation, as well as leaving a lower level of silver halide left in the emulsion.. Also, extended times in either fixer reduced density slightly, but much less reduction in Rapid Fix (even at equal times). One of the conclusions: in this application, Rapid Fix gave more resistance to microspots. They point out that actual "long term" keeping data is needed to back up the results of their accelerated test. Note: the storage materials/environment were implicated in some of the actual astronomical plates with microspots.
Since you asked for comments, my own thoughts (no warranty or supporting references) are: iodide in solution clearly slows down the rate of fixing, but waiting for film to clear and double the time (or a little more) ought to pretty adequately "fix" your material, whether sodium OR ammonium type fixer. The downside is that the sodium fixer takes longer, thus has longer to penetrate and adsorb; it dissolves more "image" and probably leaves more thiosulfate behind after washing. (Note: there is a school of thought that SOME residual thiosulfate MIGHT be preferable to NONE.) Anyway, ammonium type fixer is probably preferable but sodium type is probably fine. Again, just my unsupported opinion. PS, I don't have any idea what AA's method was, but I'm sure it's solid.