Re: When to tone?

From: bobkiss@caribsurf.com
Subject: Re: When to tone?
Date: Fri, 14 Nov 2003 09:24:13 -0400

[stuff omitted]

Frankly I don't think you would get active opinions about such a
comment by James unless you go ask gelatin specialists then at
Polaroid, 3M or other photographic manufacturers' laboratories which
were active at gelatin research. Because your question was stated
rather vaguely, and because gelatin is such a complex material, I
don't know what to say, or what to add to it. James was most active in
research of the mechanism of silver development from 40's to 70's, and
I'm curious what made him to give a lecture on the subject of gelatin
and permanence issues.

Although those reactions between thiosulfate and gelatin may occur,
when discussing practical impact of storing prints washed to a
marginally archival standard for a few weeks, there are other factors
as well. Such a reaction is generally very slow, especially in ideal
storage conditions of low humidity and low temperature in absence of
light. I cannot say much more than that in this context.

Also, accelerated aging tests in 80's seem to agree that archival
standard for residual thiosulfate prior to that date was a bit too
excessive. It is now known that prints can take more residual
thiosulfate than previously thought to be the limit for archival
purposes, and current standard is based on "life expectancy" instead
of archival vs. non-archival (partly because the term archival is
often abused and many people don't recognize its technical meaning).
Washing out residual fixer is still very important, but we now know
more more serious factors such as oxidative attacks from environmental
pollutants. This problem is very effectively solved by sulfiding
treatment of image forming silver.

--
Ryuji Suzuki
"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)