sistan

removed account4 · May 31, 2011

i was wondering if someone can answer a few questions for me about sistan.
i understand it has been used to undermine the effects and protect paper from
pollutants and atmospheric contaminants, and some suggest a way
of archivally stabilizing prints instead of using selenium or other toners.
i was wondering if anyone can tell me if i soak a print in sistan,
instead of selenium toner, if it will alter the composition of the print ( like toners do)
what sort of toxicity and disposal issues are related to sistan.
agfa isn't around anymore, who makes sistan now ?

i would rather not use selenium if i don't have to -

thanks

john

anikin · May 31, 2011

There are couple equivalent products available at freestylephoto.biz: adolux adostab, and ag STAB. Neither one alter composition of the print. Instead they work by creating a protective coating somewhat similar to how final rinse does it in C-41 process. In my understanding it is not a perfect replacement for a toner since silver still remains in the vulnerable state - the best archivability is only achieved by full toning AND applying agstab. However, if toning simply does not work for aesthetic reasons, then in theory you should at least apply sistan-like product to improve changes of your print.

jochen · Jun 1, 2011

Hello John,
Sistan consists of a aqueous solution of potassiumthiocyanate (KSCN), also known as potassiumrhodanide with addition of a surfactant (octylphenol-ethoxylate like Triton X 100). It is important not to wash the print after the Sistan-bath, the KSCN has to remain in the emulsion layer and forms a protective layer on the surface of the silver grains and it forms insoluble and immobilized silverthiocyanate if the silver gets oxidized to more soluble by an aggressive environment or by oxygen radicals which are formed by irradiation of the titaniumdioxide pigments in the coating of RC-papers and therefore prevents that the mobile silver compounds migrate to the surface of the print. Sistan does not change the colour of the silver.

thefizz · Jun 1, 2011

AG Stab is the new name for Sistan, I use it on film (instead of photoflo) and prints after toning.

removed account4 · Jun 1, 2011

sorry to ask an alternative use for it ...
but can it be used in place of selenium toner
when pre-fix toning POP prints ?
or will the silverthiocyanate be washed away
is goldthiocyanate(?) what is formed when using gold toners ( gold borax ) ?

thanks for all your helpful answers !
john

tkamiya · Jun 1, 2011

If one is to put SISTAN protected print side by side with untoned naked print, would one be able to tell any difference? I see it doesn't change color or tone but what about surface texture and reflectivity? I'm interested in this product as well....

trexx · Jun 1, 2011

tkamiya said:
If one is to put SISTAN protected print side by side with untoned naked print, would one be able to tell any difference? I see it doesn't change color or tone but what about surface texture and reflectivity? I'm interested in this product as well....

After the prints are dried you cannot tell the difference. After 3 months in displayed in sunlight the Sistan print will still look new.

Smudger · Jun 2, 2011

Sistan..

I noticed that B&H list Potassium Thiocyanate hotographers Formulary brand :US$22.95 for 100gm.
Seems to me you could make your own Sistan : if anyone knows the concentration of active ingredients,perhaps they could contribute to the thread.

anikin · Jun 2, 2011

There was a recent thread on that. From my records it's 15-20% KSCN plus 5-10% Polyoxyethylated Octyl Phenol (Photo Flo) in water. Dilute 1+19 before use. I don't know if there are other ingredients...

Rich Ullsmith · Jun 2, 2011

So, that would be what, about five or ten grams KSCN and about 5 mil photoflo in a liter of water. Is this a one shot deal, or does it have some shelf life?

anikin · Jun 2, 2011

Sorry, I have not tried it, this formula is just a derivative from MSDS. For the original sistan, the capacity was
2 sqm per liter of working solution (40 sheets 8x10). They say the concentrate will keep indefinitely. Don't know about the working solution.

brianmquinn · Jun 2, 2011

I tried to reuse Sistan but I found a working solution of Sistan goes bad quickly. In the dilute solution you will get bacterial and or fungal growth quickly. I not keep it longer than a week. Since I only do my darkroom work less than once a week it is a one shot solution for all practical purposes for me. I also find it to be too concentrated when used with film. It leaves drying marks for me. Not a problem if I squeege the film but I don't like to do that.

polyglot · Aug 27, 2014

Thread revival!

I just scored some Ag-Stab. It tells you the dilution (20:1) and a bunch of googling tells me that a minute in the bath is enough for the emulsion to soak it up. However, there doesn't seem to be much in the way of guidance as to how much capacity it might have. It seems to me that there is basically no chemical reaction occurring with a fresh print going into Sistan, the point is that it waits in the emulsion to convert any freed Ag+ ions to silver thiocyanate.

So would it be reasonable to presume that the limiting factor to its capacity is carry-over and/or mould growing in stored working solution? Has anyone tried using an antimicrobial agent like benzalkonium chloride to preserve working solutions? It seems to work nicely in my Jobo-water!

ozphoto · Aug 27, 2014

Found this on the Macodirect site (http://www.macodirect.de/chemistry-...=en&osCsid=3a7c1949b620bd40f0b40ba30eabd724):

"YieldUp to 2 m2 of film (equivalent to approx. 30 – 40 35 mm or roll films) or 2 m2 of black & white paper (equivalent to approx. 45 sheets 17.8 x 24 cm) per litre ready solution. The solution can be used down to the last drop.

Storage life
The concentrate will keep virtually indefinitely in closed bottles. The ready solution should not be kept in open trays but rather in closed bottles."

Not sure if it answers your question though, polyglot.

polyglot · Aug 27, 2014

Close enough, I hope. I'd seen the 40m^2/L (conc) number but wasn't sure if that was reaction/pollution/dilution limited or what. Nice to know I can use it down to nothing and that bottles will keep it OK.

The numbers don't really add up though; 2m^2 is 40 of 8x10 which in my experience, will not carry away anywhere near 1L of solution!

David A. Goldfarb · Aug 27, 2014

I've had batches go for years.

Gerald C Koch · Aug 29, 2014

Some years ago it was noticed that prints where all the thiosulfate had been removed had poor stability. At one time Kpdak published a formula called HE-1 which used ammonia water and hydrogen peroxide to do this. A trace of thiosulfate in the print decomposes to various sulfide compounds which react with the silver and protect it. A dilute solution of a thiocyanate serves the same purpose.

BTW, research on archival permanence for microfilm has showed that only treatment with sodium sulfide guarantees true permanence. Selenium is not as effective as sulfide. Unfortunately when using toning, for either to work that image tone MUST change. Hence the development of such products such as Sistan.

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