[pure-silver] Re: Hardening fixer for film

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <pure-silver@xxxxxxxxxxxxx>
  • Date: Mon, 16 Apr 2007 09:31:29 -0700


----- Original Message ----- From: "Snoopy" <snoopy@xxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, April 16, 2007 9:05 AM
Subject: [pure-silver] Re: Hardening fixer for film


At 17:10 16.04.2007, you wrote:

Sistan can cause problems if too much of it is left in the emulsion. Agfa never seemed to settle on definite instructions for its use.

Dear Richard,

OK, I did see that AGFA claims in their data sheet, that the Institute for Image Permance say that Sistan is as effective as Selenium Toning for image permanence.

So there seems to be no problem with that, at least for prints.

AGFA does point out in its datasheet that prints can become splotchy when Sistan is too concentrated and you are warned to make sure to stick to the recommended dilution, agitate evenly and ensure even flow over the print.

Also they clearly state that you should NOT dry prints treated with Sistan when they are on top of each other. Sistan might drip down onto the lower print and can cause concentration differentials which then lead to the staining (as Sistan then gets more concentrated when it dries).

This is from the German data sheets, it might be that the English versions were less clear nd less detailed.

Love
Snoopy

It would be interesting to know when IPI tested Sistan. A few years ago I had considerable correspoindence with Dr. Douglas Nishimura of IPI about several permanence issues. He mentioned that Sistan had never been given a formal test. I have to go by memory but I think he said that they started to test the stuff and Agfa withdrew it. Fuji makes a stabilizer that is used in a similar way but uses a different chemical. Fuji sells it only in Japan. Fuji ran controlled tests on it and found that while it provided significant resistance to oxidative attack it was not the equal of a sulfiding toner. Again, these stabilizers have the advantage of not changing the appearance or crystaline structure of the image. The last is important for microfilm where a change in the morphology of the image could damage some of the information content. The two ingredients listed on the Sistan box are Potassium Thiocyanate and a long chemical name for a wetting agent sold as Triton-X. Thiocyanates were used in one form of the old stabilization process. This was a rapid access system using fiber paper. The paper was not fixed but rather treated in a stablizing bath which prevented the image from darkening and staining for a considerable time. The resulting prints were not permanent but could be made so by subsequent fixing and washing. I will write Dr. Nishimura and ask if IPI made tests of Sistan subsequent to our correspondence.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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