Sodium Thiosulfate fixer

I just read in "The Film Developing Cookbook" the following: "The most current research indicates that sodium thoisulfate, the photographer's standby for most of the 20th century, cannot adequately fix modern films or papers. This appears to be due to the increased use of iodide in contemporary films and papers. If an acid fixer is to be used, use only acid 'rapid' fixers based on ammonium thiosulfate". As I have been using the methods recommended in AA's "The Negative" and "The Print" for some time now, this has me concerned about the archival quality of my processing. Any comments?

I use sodium thyoisulfate (pure hypo) only, it clears my film in 2-4

minutes depending on freshness, none of my negs show any problem after

30 years, now that is not archival but it is good enough for me. Don't

believe everything you read, try it and see if it works. Pat

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?

 

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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.

 

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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.

J.L.

 

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Check the archives in the Printing and Finishing Board here. We recently had a rather "lively" discussion about the use of rapid fix and archival processing of prints.