Re: Sistan Formula

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, December 10, 2005 4:43 AM
Subject: Re: Sistan Formula

> As far as I know, there is no published formula for
> Sistan. If you see
> a "formula" based on guesswork from MSDS, I would be very
> leery of
> using it for various reasons. We know that the active
> ingredient of
> Sistan is thiocyanate but in order for the effect to be
> optimal, the
> amount is very critical; too much thiocyanate is badly
> harmful, and
> too little is ineffective.
>
> A better option is Fuji Ag Guard. This product uses a
> superior
> compound (an organic thiol compound) which has a wider
> window of
> effective dose. However, the solubility of this type of
> compound is
> generally very small (Fuji made one that is reasonably
> soluble, but
> still they cannot make highly concentrated stock like
> Sistan). Availability of this product outside Japan is
> also limited.
>
> If you want to use any homemade counterpart of these
> products, I can
> tell you more about what I know about how these things
> work, but I'll
> also have to tell you that you MUST test for efficacy of
> treatment, at
> least by peroxide fuming test at high humidity condition.
> There are
> some well known compounds that can be effective in
> protecting image in
> one way but very detrimental in different ways in certain
> conditions. This is the kind of things you want to be
> extra careful
> when discussing image protecting agents.
>
> The easiest way is to stick with well tested
> products/methods.
>
> Ryuji
>
   My understanding is that Sistan and Ag-Guard are
effective but less so than a polysulfide toner like Kodak
Brown Toner, do you agree? If so perhaps the use of the
toner is a better alternative than attempting to make a home
made version of Sistan.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com