[pure-silver] Re: Testing Washing with Selenium Toner 1+9
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Tue, 26 Oct 2010 19:50:17 -0700
----- Original Message -----
From: "Elias_Roustom" <elroustom@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, October 26, 2010 6:28 PM
Subject: [pure-silver] Re: Testing Washing with Selenium
Toner 1+9
Thanks Richard. I wet the print by running water over the
corner I was testing. This was a practice print to test
several things at once including a new washing routine... so
I'm not worried about the stains.
Residual silver? So that's testing for sufficient fixing
then?
So to test my washing, I need to get some sodium sulfide.
Elias
Selenium toner works fine for testing for residual
silver, that is, for the effectiveness of the hypo. Either
selenium or sulfide will tone remaining silver halides or
silver-thiosulfate complexes as readily as it will tone
metallic silver. For testing for _residual hypo_ that is
effectiveness of washing, you need a solution of silver
nitrate. This is used in the same way as the residual silver
test, that is a few drops of the diluted solution is placed
on a clear area of the negative or print and allowed to
stand for two or three minutes, then blotted off. It should
leave no more than a very slight stain. Kodak used to offer
a chart showing stain levels, there is one in the _Kodak
Black-and-White Darkroom Dataguide_ which is available in
various editions used. This chart can be used for both tests
but the residual silver test should really show NO stain.
The silver nitrate test will result in a permanent
stain so should be used only on a border area of a negative
or a scrap of printing material processed with the print or
on a border that will be trimmed away when mounting. There
is a more elaborate version of the silver nitrat test that
fixes the stain so that it can be measured with a
densitometer. This is then compared to samples that have
known amounts of hypo in them. Kodak has this all detailed
somewhere in its technical papers. The more modern
measurement for residual hypo is the methylene blue test
that is detailed in a ISO standard for quantitive
measurements. Its much too elaborate for routine use.
The silver nitrate and sodium sulfide test are detailed
in the Kodak handbook. The KRST test has not been included
for many years because I think it led to misleading results
too often when used on inadequately washed material. Its
quite reliable when used on washed film or paper.
Keep in mind that the results are those obtained
immediately after making the test because both tests darken
with time.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
