[pure-silver] Re: Selenium toning + Agfa Sistan

----- Original Message ----- 
From: "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>; <info@xxxxxxxxxxxxxxxx>
Sent: Tuesday, November 30, 2004 2:40 PM
Subject: [pure-silver] Re: Selenium toning + Agfa Sistan


> From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
> Subject: [pure-silver] Re: Selenium toning + Agfa Sistan
> Date: Tue, 30 Nov 2004 23:26:44 +0100
>
>> I'm sure you're toning your prints for a certain length 
>> of time. Is the
>> silver conversion 100% complete at that point in time? Is 
>> it at half that
>> time? Is it at 10% of that time?
>>
>> I may not tone to completion, because I may dislike the 
>> color change. In
>> that case, I like the additional protection of Sistan.
>
> That's not the point. You initially said "these toner 
> conversions are
> never 100%" and I'm simply pointing out that that is 
> incorrect. You
> are simply saying that you chose not to tone 100%. That's 
> a very
> different thing.
>
> --
> Ryuji Suzuki

    It would be interesting to know the original source of 
the statement. As you know there is a lot of misinformation 
in the popular literature.
    I know of no published accelerated aging tests of 
Sistan. I have seen a paper with some tests of Fuji 
Ag-Guard, but it uses a different chemical than Sistan. Ag 
Guard provides substantial protection but not as much as 
proper toning. I suspect that Sistan is similar in that it 
gives some protection but not up to a toned image. Its 
advantage is that it does not change the color or density of 
the image.
   I will also add that complete conversion may not be 
necessary for maximum image protection by the toner. IPI 
recommends a 60% conversion for its polysulfide toner as 
determined by densitometric testing. This is not to say that 
this is better than complete conversion, only that the 
criterial of complete conversion may be someone's guess not 
based on testing.
   Also, microfilm is not the same as pictorial film or 
printing paper. The requirements for toning it are that the 
crystal structure not be changed enough to destroy any data. 
This is not a criteria for pictorial photography where 
different toners and amounts of toning are acceptable.
   I am basing these statements on the NIH report and on 
personal conversations with Dr. Nishimura.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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