[Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

`Richard Knoppow dickburk at ix.netcom.com
Fri Aug 18 04:44:09 UTC 2017


    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



More information about the Alt-photo-process-list mailing list