[pure-silver] Re: testing for complete fixation
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 16 Aug 2007 20:57:59 -0700
----- Original Message -----
From: "hksvk" <hksvk@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, August 16, 2007 2:31 PM
Subject: [pure-silver] testing for complete fixation
Back in March, Richard Knoppow stated:
can test for completeness of fixing by using either a
Sodium sulfide
test or a solution of KRST diluted 1:9. The KRST must be
used on well-washed prints or films because it fails where
there is an excess of fixer.
Should the print be wet or dry or doesn't it matter? Is
this true for both
KRST and the sodium sulfide tests?
If the stain is any intensity ranging from barely
perceptible to grossly
yellow or orange, does this mean fixation was not
complete, ie., there is
residual silver halide there? If so, does the stain appear
right away, or
does it take a few minutes or longer?
Thanks, Richard.
Harry
At one point Kodak was recommending a 1:9 dilution of
KRST as an alternative to the Sulfide solution but no longer
does. It may have proven unreliable for other reasons also.
The Sulfide or KRST test for completeness of fixing, not
for residual fixer. These two tone silver halide and fixer
reaction products as readily as they tone meallic silver,
more readily in the case of Sulfide.
Residual hypo is tested using a solution of Silver
Nitrate, usually preserved with a little Acetic acid. It
produces a similar stain and the Kodak Hypo Estimating
strips can be used for both tests. The Silver Nitrate test
can show a very light stain even hypo is below the desired
level so it should never be used in the image area of a
print or film.
There is a method of fixign the stain using a solution
of Sodium Chloride and fixing. This is used to get
comparison density measurements where a set of standards
exists. Kodak has described this method completely in one of
its research papers but I will have to do some looking to
find the one and cite it.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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