[Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

Marek Matusz marekmatusz at hotmail.com
Fri Aug 18 16:10:43 UTC 2017


I am trying to put some knowledge from the B&W photography days into salt printing practice and be somewhat scientific about it. I have seen a lot of early photographs in the salted paper family (this would include albumen prints, collodion papers and others) and they all show some image deterioration. Actually the only early photographs that looks like they just came out of the photographers studio that I have seen are carbon transfer prints. Maybe one day I will make it to the Eastman Museum to study the vast collection there.


In any way I am continuing to investigate salted paper process and stability of salted paper prints. The fixing process and what it does to the salted paper print is least understood part of it. Thanks to Chris that gave me the bug!!


Marek


________________________________
From: Alt-photo-process-list <alt-photo-process-list-bounces at lists.altphotolist.org> on behalf of `Richard Knoppow via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org>
Sent: Friday, August 18, 2017 4:44 AM
To: Ryuji Suzuki
Cc: `Richard Knoppow via Alt-photo-process-list
Subject: Re: [Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

    OK, all now in place. Yes, it was Sistan I was thinking of. and Ag
Guard was supposed to be more effective.
    I like wet photography but have never done it professionally. I am
afraid digital has it all over chemical photography for commercial
purposes.

On 8/17/2017 9:38 PM, Ryuji Suzuki wrote:
> No worries, the world moved on, and I moved on, as far as professional
> life goes. I spend much of my time as commercial and portrait
> photographer and, guess what, I shoot digital for those, although I
> have many of my silver prints on my studio walls, two Durst enlargers
> standing here, and boxes of films and film a few film cameras on my
> desks.
>
> Agfa had a product called SISTAN, which was essentially a finishing
> surfactant (wetting agent) with a very dilute thiocyanate mixed in.
> There was a controversy as to what was the range of safe and effective
> concentration, because above a certain level of thiocyanate
> concentration, this agent was actually detrimental. Too weak, and it
> was ineffective. AGFA itself revised their recommendation. Independent
> research to replicate their claim was limited. That is what you
> (Richard) was worried about back then.
>
> Fujifilm had a product called Ag Guard. This product had an advantage
> over SISTAN because there was no harm using too much or too strong of
> a solution. But it wasn't sold outside Japan, and it also used an
> organic compound that was not readily available. The compound is also
> not exactly easy to synthesize (see the patents referenced from my
> paper). Ag Guard was one product that would be not exactly impossible
> but absolutely cost prohibitive if you tried to mix your own, even
> after the patent expired.
>
> I was looking for a compound that would be readily and inexpensively
> available even after the silver halide imaging industry is completely
> gone and still very effective for image protection. One of the
> anonymous reviewers apparently didn't like this part and advocated to
> use Ag Guard for image protection purposes, which made me guess that
> the editor sent my manuscript to the guy who invented Ag Guard (but of
> course, there is no way to confirm that). I think the other reviewer
> was a very well informed professional conservator and s/he was very
> positive about my work.
>
> One caution. Thiourea was mentioned as potentially useful image
> protecting agent for many reasons in some places, but there was no
> published work proving or clearly rejecting this. I tested it (not in
> this paper), and I should say that this compound shouldn't be used as
> a protecting agent for silver image. It slowly discolors silver image
> over the course of a few years in normal storage conditions. Not
> exactly in the context of protecting developed out silver image, but
> guess who knew that many decades prior, and that was of course James.
>
> Ryuji Suzuki
> "The essence of the beautiful is unity in variety." (Felix Mendelssohn)

--
Richard Knoppow
dickburk at ix.netcom.com
WB6KBL

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