This is related to the idea that a small amount of residual
thiosufate helps to protect the image. Thiocyanate is also a
fixing agent. It may have been found to work in a similar way. I
have never seen a technical paper on thiocyanate used this way.
The thiosulfate is supposed to result in some sulfiding of the
silver. Thiocyanate may do the same thing. It is the sulfide that
protects the image.
On 8/8/2021 7:34 PM, Jean-David Beyer (Redacted sender jeandavid8
for DMARC) wrote:
On 8/8/21 6:26 PM, `Richard Knoppow wrote:
Sistan is apparently a mixture of thiocyanate and a wetting agent. So,As I recall, thyocyanate is a fixing agent. So there must be more in
its used in place of a wetting agent as the last step where it will not
be rinsed out by a subsequent bath. One complaint about it had to do
with establishing the concentration of the chemical remaining in the
emulsion. If the stuff works it has some advantages over toning.
Sistan that that and a wetting agent if it is meant to protect prints
better than washing in water.
