[pure-silver] Re: Fixer Stain Removal
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 9 Nov 2009 13:50:31 -0800
----- Original Message -----
From: "Jean-David Beyer" <jeandavid8@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, November 09, 2009 2:54 AM
Subject: [pure-silver] Re: Fixer Stain Removal
Richard Knoppow wrote:
----- Original Message -----
From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, November 08, 2009 4:21 PM
Subject: [pure-silver] Fixer Stain Removal
What is the latest wisdom on removing fixer stains? I've
tried a 50%
citric acid solution with limited success but like to
get something
more 'agressive'.
Regards
Ralph W. Lambrecht
Describe the stains. If they are silver stains you
may have success by using fresh acid rapid fixer with
added citric acid, about 15 grams per liter. This is a
mild solvent for metallic silver. For sulfide stains I
think one has to resort to stronger bleaches like Kodak
TC-3.
Solution A
Water 1.0 liter
Potassium permanganate 2.0 grams
Sulfuric acid (concentrated) 4.0 ml
Store in a stoppered bottle away from light.
Solution B
Water 1.0 liter
Sodium bisulfite 30.0 grams
Sodium sulfite, desiccated 30.0 grams
It appears that the sodium metabisulfite of commerce is
the same substance as called sodium bisulfite in Kodak
formulas.
To use treat stains with a small amount of Solution A,
then rince well and treat with solution B. Then wash.
I will look at some other sources for clothes specific
stain removers.
If I remember my chemistry correctly (about 50 years ago),
you cannot purchase sodium bisulfite because it does not
exist in solid form. Sodium metabisulfite is readily
available in solid form and absorbs water to become sodium
sulfite when mixed with water. Wikipedia does not hold
this opinion and describes each. the bisulfite one is
HaHSO3 and the metabisulfite is Na2S2O5. In other words,
they are really the same compound, but the one is a
dessicated form of the other and perhaps both exist in the
dry state. Now what you have if you cannot keep them both
dry enough is anybody's guess, probably a mixture of each.
We should from what substance the O.P. wishes to remove
the stains. If it is something like a metal tray, or
perhaps even a plastic tray, TC-3 would be fine, but if it
is on clothing, that may be too strong and damage it.
--
.~. Jean-David Beyer Registered Linux User
85642.
/V\ PGP-Key: 9A2FC99A Registered Machine
241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 05:35:01 up 2 days, 12:09, 3 users, load average:
5.19, 4.74, 4.47
TC-3 was recommended for removing silver stains from
the hands so it can't be too strong but some cloth is pretty
delicate.
There was a long discussion in one of the lists or,
perhaps, in the darkroom Usenet group about sodium
bisulfite. That is why I mentioned the metabisulfite. The
bisulfite specificed by Kodak is actually the metabisulfite.
Kodak evidently used some old chemical terminology, but then
these formulas are all quite old. This is also true of
Ansco/Agfa formulae and probably all other photographic
formulae of the time.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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