[pure-silver] Re: Iodide in emulsions...
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 27 Nov 2009 12:37:03 -0800
----- Original Message -----
From: "Ray Rogers" <earthsoda@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, November 27, 2009 6:42 AM
Subject: [pure-silver] Iodide in emulsions...
--- On Wed, 11/25/09, Richard Knoppow
<dickburk@xxxxxxxxxxxxx> wrote:
Iodide
used to be found mostly in film emulsion but it is now
also
found in paper emulsions especially variable contrast
emulsions.
Hi Richard,
Sorry to have to call you on this, but on what basis do
you make this claim?
There is to my knowledge, no relatonship between iodide
and variable contrast paper emulsions.
Iodide does find some use in paper emulsions, and has for
many years in certain products, and, although this fact
was not that well known, it was not a really a secret
either; it was just present in very small quantities that
did not draw much comment.
Where did you get the notion that iodide was in some way
related to variable contrast?
I only bring this up in hopes you might actually have a
source for that claim.
Ray
I have now forgotten the source but it seems to me to
have been a reliable one, possibly Haist's book. I am not
sure of the reason but I think sensitivity in the green may
have been part of it although color sensitizing is done
mostly with dyes.
A curious thing is that it used to be recommended that
film and paper not be fixed in the same bath, mostly due to
the accumulation of iodide from the film. But... adding some
iodide to the fixing bath was at one time recommended as a
way of accelerating wash rate. In any case, it appears that
two bath fixing pretty much obviates this concern.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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