[pure-silver] Re: Mystery Hypo Test
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 22 Nov 2009 15:34:41 -0800
----- Original Message -----
From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, November 22, 2009 2:35 PM
Subject: [pure-silver] Re: Mystery Hypo Test
Richard
That's good, but keep in mind, just as the book suggests,
I'm
interested in this formula as a substitute for HT-1 not
HT-2. My goal
is to have a better hypo test for film without going to
methylene-blue.
Regards
Ralph W. Lambrecht
http://www.darkroomagic.com
The first residual hypo test was one using potassium
permanganate to test water run off from the print or
negative. The problem was that the run off water could be
relatively free of hypo while excessive hypo was bonded to
the emulsion and support. It was not a satisfactory test
despite being published for years. Its replacement was the
silver nitrate test. This is practical and sensitive enough
to determine when material has been washed down to archival
levels. The methylene blue test is the newest but is mostly
for specialized uses such as research and microfilm since it
is rather complex.
HT-1 and HT-1a are the permanganate test. The 1940
edition of _Photographic Facts and Formulas_ also contains
the mercuric chloride test attributed to Crabtree and Ross
but without a citation. I think this is not a very
satisfactory test and evidently was not used for long. This
does confirm my first impression that it was a very old
test. The most satisfactory test for general use is the
silver nitrate test Kodak HT-2. Again, HT-2 can be made
quantitative by fixing the stain. I will have to find the
method. I doubt seriously if HT-1 works better or is more
sensitive.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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