[Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

Ryuji Suzuki rs at silvergrain.org
Fri Aug 18 04:38:17 UTC 2017

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 

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 

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)

On 18 Aug 2017, at 0:03, `Richard Knoppow wrote:

>    I could not remember the name of AGFA Ag guard or would have 
> mentioned it before. I am glad to see you researched it and found it 
> effective since there was some doubt in popular literature. I must 
> still have several bottles of it.
>    I am sorry to hear that no one is interested in silver image 
> protection any more. I am sure that is very discouraging.
>    I am not sure of the title of James paper that I was thinking of, 
> something very similar to the one mentioned.
> On 8/17/2017 8:55 PM, Ryuji Suzuki wrote:
>> I forgot to advertise my own work.
>> Fujifilm Ag Guard is effective in protecting silver image from 
>> oxidative attacks (that is not my work, though I confirmed it 
>> myself).
>> So is an alkaline solution of 2-mercaptobenzimidazole (formula in my 
>> paper)
>> http://adsabs.harvard.edu/abs/2011JSPST..73..180S
>> The actual paper in PDF (Japanese language only) is here:
>> https://www.jstage.jst.go.jp/article/photogrst/73/3/73_3_180/_pdf
>> I sent it to Doug Nishimura and Gawain Weaver and asked if it's worth 
>> publishing in English. Some said no one was researching conservation 
>> of silver imaging material (no more research funds).... don't bother. 
>> Some also cautioned me that professional conservators are discouraged 
>> from performing any process that chemically alters the image, silver 
>> or otherwise. Although Ag Guard and 2-MBI do not alter the image 
>> itself (that is the point of this approach, as opposed to toning), 
>> and this point is explained in the paper, the distinction probably is 
>> not very clear to average conservators. So, no, there is no English 
>> version published anywhere. (Besides, this journal was one of the 
>> very few last remaining journals that published new researches on 
>> silver imaging... at that time back in 2010/2011.)
>> Ryuji Suzuki
> -- 
> Richard Knoppow
> dickburk at ix.netcom.com

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