Sodium Thiosulfate not adequate for paper anymore?

[konakoa]

Going through my bookshelf I was glancing through several titles. In one, The Film Developing Cookbook, Bill Troop says that for modern papers the standby classic sodium thiosulfate really doesn't work anymore as all the papers we have now contain iodide. He further mentions that even ammonium thiosulfate rapid fixers have trouble with it.

As I've been using sodium thiosulfate as a bulk scratch-made paper fix for a good number of years this got me thinking. And worrying. Have I properly fixed my prints? Or have I ruined many years of work with a fix that won't...fix?

Can any chemists reading here confirm this sodium thiosulfate and iodide issue?

 

[Gerald C Koch]

What appears in the Film Developing Cookbook should be taken cum grano salis.

BTW, the first edition of this book has a number of errors, some serious. I don't know if the errata is still available online.

 

[Photo Engineer]

Bill is right about the Iodide, but wrong in that at the published times Sodium Thiosulfate does not work. You need more time in the fix and more time in the wash. Now, this is particularly true with the Kodak papers I tested, but not so much with the Ilford papers (back when there were Kodak papers). Also, some second and third tier papers varied quite a bit in this regard. I adjusted my fix and wash times accordingly after running the tests and talking it over with Bill.

Now, I have a question: Don't you test your prints for Hypo retention or Silver retention? The little dropper bottles of chemicals are so inexpensive and reassuring! If not, then get them and test your prints!

PE

 

[konakoa]

Thanks Gerald and Ron. I brought this up as I also read a paper online by Michael Gudzinowicz saying pretty much the same thing re: sodium thiosulfate and iodide in modern darkroom materials. Yet I am leery of jumping to conclusions.

Ron, I am using ST-1. The paper tests as "fixed" but I'm not so sure. I say this as I'm seeing a faint yellow stain in my paper highlights. I'm using a two bath fixing solution, five minutes in each bath, ten minutes total. Rinse, hypo clear and thirty minute wash. Fix is bulk plain sodium thiosulfate crystals with a bit of sodium sulfite added in. Chemistry sourced from Photo Formulary. Fix is mixed up fresh and new right before printing.

My standard paper is Adox MCC. Also having trouble with Ilford Warmtone paper showing the same yellow tinge, although with that paper it's far more pronounced. It's especially noticeable on the print borders.

The goofy thing is selenium toning helps to clear it up. Identical prints, one toned, the other untoned and placed side by side really shows a marked difference. The borders in the untoned print can be slightly yellow in one print, much brighter and cleaner in the toned print. Going through the toner (KRST is apparently loaded with ammonium thiosulfate) helps to clear up the prints. Again, I don't want to guess, but that's what makes me suspicious of my sodium thiosulfate fix.

Any thoughts?

 

[Gerald C Koch]

You can speed up the fixing rate of a sodium thiosulfate bath by adding 50 g/l of ammonium chloride. An example of this is Agfa 304 Fixing Bath

 

[Photo Engineer]

Konakoa, the best archival print test shows just a hint of yellow, and from what you write you seem to be doing things correctly.

PE