[pure-silver] Re: RC to FB
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sat, 01 Jan 2005 17:45:08 -0500 (EST)
From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
Subject: [pure-silver] Re: RC to FB
Date: Fri, 31 Dec 2004 18:54:17 -0800
> Such tests were done in the 1930's by Kodak labs although
> a rather more extensive set of tests was done at Agfa by
> Edyth Wyde. Kodak discovered that alum hardener had much
> more effect than the fixer pH. For instance film fixed in
> Chrome Alum (Potassium chromium sulfate) washed out as fast
> as un-hardened film even though the pH of this fixer is
> around 2.0.
Results of studies on washing rate should be discussed with careful
attention to the condition of the tests. For example, whether the
fixing bath was loaded with silver to simulate typical operating
condition, or test was run with a fresh fixing bath with little silver
load. Whether distilled water, tap water, well water, or other water
is used has a very large impact on the efficiency of washing. Tap
water in Boston area typically has pH of 9 to 9.2 to prevent copper or
other metal leaching out of water pipes from pipes of old
buildings. In other areas, this may be different.
Based on my literature study and experiments, neutral rapid fixer
washes out of film, RC and fiber paper fast enough in my tap water.
More importantly, whenever any of this issue is important, citing past
researches does not solve the problem and the only way to get the
issue done is to run your own test. Sodium sulfide test and silver
nitrate test do not give analytical accuracy but as long as you make
sure to err on the safer side, their semiquantitative accuracy is good
enough, and those tests are very easy to perform in darkroom.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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