The OP mentioned the Delta films. IIRC, the Delta films
Originally Posted by nworth
are thought of as being iodized. It is common knowledge
that Rapid fixers Slow way down with such emulsions.
Rapid fixers, with such films, become little faster
than a sodium fixer.
Fixer capacity is much reduced, Sodium or
so using TF-2 (alkaline sodium thiosulfate fixer) with Delta (or T-Max or Neopan) films should be OK and archivally stable?
measured clearing time with Delta 400 is about 2 mins 15 sec and fixing for 10 minutes aren't problem for me (and it doesn't hurt film - everything looks good).
the whole question is only about archival stability of modern films fixed by sodium thiosulfate, nothing else.
I started using TF-4 with 510 Pyro, but have since switched to Kodak fixer wilth no problems. Shipping water is just too expensive.
I tested this with Ilford MGIV and it was measurable after 8 minutes.
Originally Posted by Ian Grant
Look at it this way, for ourselves there is no substitute
Originally Posted by Lukas_87
for thiosulfate. And it's been that way since the 1850s
when it was discovered that thiosulfate will complex
with silver and hold it in solution: that is, will make
soluble non-image silver.
Ammonia is the RAPID part of Rapid fixers. It alone
will make soluble the chlorides of silver but does
poorly with the bromide. It has very little effect
on the iodide of silver. So, Rapid fixers are
slowed in the presence of silver iodide.
Sodium or ammonium, it is the thiosulfate which
carries the load. Thiosulfate along with cyanide
are two compounds which have great affinity
for the silver ion.
Rapid fixers became popular in the latter
50s and 60s. Now days I use fresh brewed
unadulterated S. Thiosulfate and use it very
dilute one-shot, film and paper. Dan
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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 http://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!