[pure-silver] Re: Edwal Hypo Test and Poor memory
- From: John Meyers <jmeyers102@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 10 Jan 2011 15:55:34 -0800 (PST)
I wouldn't doubt that Richard is correct about Edwal Hypo-Chek not being a
reliable test. But to answer your question, below are the instructions from my
bottle of Hypo-Chek:
FOR HYPO FIXERS: Add 2 drops Hypo-Chek. If a white precipitate forms, discard
the fixer.FOR HIGH SPEED FIXERS: Dip out 1 or 2 ounces of the fixer. Add 1 or 2
drops of Hypo-Chek and shake. When a permanent milkiness remains, the fixer
should be discarded. Hypo-Chek will not harm any fixing bath.
John Meyers
--- On Mon, 1/10/11, Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
Subject: [pure-silver] Re: Edwal Hypo Test and Poor memory
To: pure-silver@xxxxxxxxxxxxx
Date: Monday, January 10, 2011, 5:52 PM
----- Original Message ----- From: "Eric Nelson" <emanmb@xxxxxxxxx>
To: "pure silver" <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, January 10, 2011 10:56 AM
Subject: [pure-silver] Edwal Hypo Test and Poor memory
> My bottle of Edwal hypo check test's instructions on the bottle are worn off
> and
> as I remember the instruction for testing paper rapid fixer was to add a
> couple
> drops to an ounce or so, (I used 10-20 mls in a graduated cylinder) and
> swirl the mixture. If the milkiness disappears, then it's still good.
>
> Can anyone confirm this from their bottle or experience? Just want to make
> sure
> my memory isn't completely awol.
>
> Thanks
> Eric
>
>
My bottle of HypoCheck is not available at the moment but its not a
reliable test anyway. Hypo Check is a solution of iodide and forms silver
iodide when added to the hypo. The problem is that the reaction depends on the
consentration of the solution and, in any case, its not very sensitive. Kodak
has a formula for a similar test solution in the _Black and White Darkroom
Dataguide_ and elsewhere.
A much better test for the fixer is to fix out a scrap of paper or film and
use the residual silver test published by Kodak. If the sample is washed before
testing you can use a 1:9 dilution of Kodak Rapid Selenium Toner rather than
the sodium sulfide solution in the published formula. The KRST test fails if
there is a lot of hypo in the emulsion so it should be washed, at least
briefly. If the fixer is working the test should produce NO stain. Its used on
wet but blotted emulsion. Place a drop on a clear area and allow it to stand
for about one minute, then blot off. There should be no visible stain. If used
on a print wash the print as you would after toning because the residue of the
toner will eventually cause a stain.
Here are some formulas for test solutions:
Kodak Fixer Test Solution FT-1
Water (at about 80F or 27C) 750.0 ml
Potassium iodide 190.0 grams
Water to make 1.0 liter
To test a single bath fixer. To 5 drops of test solution add 5 drops of fixing
bath and 5 drops of water. Discard the fixer if a yellow-white precipitate
forms instantly. Disregard any slight milkiness.
The instructions for two bath fixers do not make sense and I think the
dilutions are reversed. They recommend testing the first bath with the same
dilution as a single bath but a greater dilution for the second bath. Since the
sensitivity of the test decreases with dilution I think this is opposite of the
correct practice. Kodak recommends taking 5 drops of solution, 5 drops of
fixer, and 15 drops of water for the second bath. I think probably this applies
to the _first_ bath and it is the second that is tested the same as the single
bath. In any case the dilution is known where it is not for the Edwal test.
Also a liter of this stuff is a lifetime supply for an army. Probably
around 100ml is a more sensible amount.
Residual Silver Test ST-1
Water 100.0 ml
Sodium sulfide, anhydrous 2.0 grams
Store in a small stoppered bottle for no more than 3 months.
For use dilute one part of the above stock solution with 9 parts water. The
diluted solution should be replaced weekly.
To use place a drop on a clear area of the print or film and allow to stand
for 2 to 3 minutes. Blot off with a clean, white blotter. There should be no
stain. Any stainging indicates residual silver halide. Note that the spot will
stain with time so the test should be made on a scrap of paper processed with
the prints or on a clear border of negatives.
The KRST test mentioned above is as effective and has no odor but will fail
to show a stain if there is much hypo in the emulsion.
Residual hypo test, a test for completeness of washing.
Residual Hypo Test Solution HT-2
Water 750.0 ml
28% Acetic acid 125.0 ml
Silver nitrate crystals 7.5 grams
Water to make 1.0 liter
Note, use distilled water. Chlorine in the water will combine with the silver
to form a precipitate of Silver chloride.
Store the solution in a screw-cap or glass-stoppered brown bottle away from
strong light at 65F to 75F (18C to 25C); it will keep for about 6 months
Apply a drop fo the solution to a clear, unepsoed area of the emulsioni sid
eof processed film that has been squeegeed or sponged. Allow it to stand for
about 2 minutes. Then rinse off the testg olution with water, blot the excess
water. The instructions are than to compare any stain to the examples printed
in the book. Kodak also made an estimation strip with example stains. Some
materials will show more stain than others but there should not ever be a stong
stain. As with the other tests this one will generate a dark stain with time.
There is a more sophisticated version of this test where the stain is fixed
with salt, it can then be compared for density using a densitometer and
prepared examples. The methylene blue test currently specified by the ISO is
more sensitive for quantitative testing but is too complex for routine tests
and this one works well enough for routine darkroom use.
To test the effectiveness of a washer entire prints should be fixed out,
washed, and immersed in the test. It will show if the washer is uneven in its
effectiveness.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx
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