Re: Sources for wet plate collodion chemicals

----- Original Message -----
From: "D. Mark Andrews" <mark@dragonbones.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, August 26, 2005 9:38 AM
Subject: RE: Sources for wet plate collodion chemicals

> Chris,
>
> If you reread my post you will clearly see that I said it
> was my
> "understanding" that Sodium Cyanide was not an appropriate
> fixer. For the
> past two years I've primarily used KCN, occasionally hypo
> is some situations
> (e.g. teaching wet plate technique to grad students). As
> far as I know,
> George Berkhofer is the only proponent of using Sodium
> Cyanide--I've seen
> his posts and seen others disagree with him. Perhaps he's
> right. Have you
> had any success using it?
>
> Perhaps "nut" is an insult where you reside, but in
> California we are all
> nuts and take great pride in it. We also like nerd.
>
> Mark
>
   Long thread snipped.
   I am not a practitioner of Collodion, this is asked out
of curiousity. My understanding is that wet plate negatives
were (and are) fixed with a cyanide salt because the halide
is Silver Iodide, which is slow to to fix in Sodium
thiosulfate. However, Ammonium thiosulfate is a better fixer
for Silver Iodide, is it not good enough for wet plate?
   Secondly, I am puzzled by the term "brightening", does
this refer to the negative or the print? Is it actually
another term for contrast, some parts of this thread seem to
suggest it is. Cyanide is a solvent for metallic silver so,
it seems to me, that excessive fixing in it would destroy
part of the very fine grain wet plate image. Is this slight
reduction what is being referred to, and if so, it is
considered desirable or undesirable?
   If undesirable Ammonium thiosulfate would seem to have
another virtue beside being relatively innocuous.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com