In The Film Developing Cookbook, p. 105, Bill Troop says that “current research indicates that sodium thiosulfate … cannot adequately fix modern films or papers”, and in a footnote cites Haist, Modern Photographic Processing, and the following article:
Lee, W. E.; Drago, F. J.; Ram, A. T. “New procedures for processing and storage of Kodak spectroscopic plates, type IIIa-J”, Journal of Imaging Technology, Vol. 10, No. 1 (Feb. 1984), pp. 22-28.
This investigation into microspot formation on astronomical plates led to a new processing procedure and storage recommendations for enhanced image stability for these materials.
Lee reports that the densitometric characteristics of plates images processed in Kodak fixing bath F-5 (sodium thiosulphate) and Kodak rapid fixer were virtually identical; however F-5 left significantly more silver halide in the emulsion layer, “indicating less fixing action” even with a total of 12 minutes in two baths of F-5 compared to 4 minutes for complete fixation with rapid fixer. Lee also found that the density loss with inadvertent prolonged fixation was proportionally worse with F-5, contrary to long held assumptions, and on the basis of these findings recommends that rapid fixer replace F-5 for this application.
Lee does not conclude that fixing with sodium thiosulphate is “inadequate”, just that rapid fixer is better for this application. More research might be desirable before generalising the recommendations arising from this study to all modern photographic materials.
Incidentally, Lee also found that hypo clearing agent had an adverse influence on permanence, as indicated by his accelerated peroxide microspot test. Later research demonstrated the benefits of a very small amount of residual hypo. Thus, current recommendations are not to use Hypo Clearing Agent for film, which should not be over-washed, and should definitely not be subjected to the HE-1 hydrogen peroxide-ammonia hypo eliminator.
Lee also recommends a postprocess treatment of Kodak rapid selenium toner, although later research demonstrated that sulfiding treatments are superior (See for example the Image Permanence Institute study at cool-palimpsest.stanford.edu/.../an12-507.html).
From a behavioral point of view, it might also be worth commenting that over-fixing is less likely if the process takes a relatively short amount of time; i.e. you're more likely to forget your film in a sodium thiosulphate fixer while you go off and do something else for the next ten or twelve minutes (even though you should be agitating the film in the fixing bath!), on the other hand, you're more likely to wait around for the precise time if you know the film needs to come out in three or four minutes!
stručně vzato se v Kodaku přišlo na to, že ustalovače s thiosíranem sodnym nedokážou ustálit moderní fotografický emulze (filmy s plochejma krystalama, moderní papíry) tak kvalitně, jako rychloustalovače s thiosíranem amonným. vysvětluje to, proč Ilford tak hrdě přidává do datasheetů ke svejm ustalovačům, že neobsahujou sodium thiosulfate (hypo).
mno...
