[pure-silver] Re: Hardening fixer for film
- From: "Steve Goldstein" <sgold@xxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 16 Apr 2007 13:11:54 -0400
Ctein talks about the image-preserving properties of Sistan in one of
the later chapters
in his book _Post Exposure_. He did a number of experiments with RC
papers untoned,
with KRST alone, and KRST+Sistan. As I recall the Sistan made a
notable improvement
in image longevity for prints exposed to light. The book is at home,
and I'm not, so I may
be a little foggy on the specifics, but Sistan definitely had an effect.
As others have stated, Sistan treatment is supposed to be _the_ last
step before drying,
and I think Agfa even advises to squeegee or wipe off any excess
liquid. Apparently just
the small amount retained in the paper and emulsion is sufficient.
HTH,
steve
On 4/16/07, Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
----- 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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