[pure-silver] Re: Adding Sodium Sulfite to Sodium Thiosufale.
- From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 3 Apr 2011 05:37:54 -0700 (GMT-07:00)
-----Original Message-----
>From: "Michael A. Smith and Paula Chamlee"
><michaelandpaula@xxxxxxxxxxxxxxxxxxx>
>Sent: Apr 3, 2011 5:13 AM
>To: pure-silver@xxxxxxxxxxxxx
>Subject: [pure-silver] Re: Adding Sodium Sulfite to Sodium Thiosufale.
>
>Bogdan,
>
>I use an acetic acid stop bath. I then use plain
>sodium thiosulfate with 15-25 grams added of
>Sodium Bisulfite per 1/2 gallon or 40-50 grams of
>Sodium Bisulfite per gallon.
>
>Many years ago, when I spent a month with Brett
>Weston, watching him print most every day, this is
>what he used. I figured if it was good enough for
>Brett, who learned to do this from his father, it
>was good enough for me.
>
>Brett used the higher number in the quantity range
>above. Paula does not like the smell of the
>Bisulfite when she gets close to it, so she has
>cut down the quantity with no adverse affect.
>
>When the Bisulfite is not used, and there is only
>the plain sodium thiosulfate, the solution soon
>gets quite cloudy (though seems to continue
>working). When the Bisulfite is added, it clears
>right up.
>
>I use a two-solution fixing bath. The first bath
>only gets the Bisulfite. Then I use a holding bath
>and at the end of the day I rotate finished
>prints through a second fixing bath, this time
>with plain sodium thiosulfite only and no Sodium
>Bisulfite.
>
>I then take the prints directly into a
>Perma=Wash/Rapid Selenium Toner Solution. I have
>never had any staining.
>
>Using 480 grams of Sodium Sulfite per two liters
>of hypo seems to me to be beyond excessive. That
>is a lot of Sodium Sulfite. Mt recommendation is
>to ignore Anchell's recommendation.
>
>Michael A. Smith
>
I think you misread Bogdan's post, it was sodium _thiosulfate_. 240 grams
per liter is about standard. I have not heard of using sodium bisulfite in
fixer but it would probably serve as well as sulfite but would be somewhat
acid. Sulfite and bisulfite for a buffer at near neutral pH. Not important for
fixer because it doesn't care about pH but acid will tend to decompose it which
is why a large amount of sulfite (15 grams per liter typically) is used in
hardening fixers using white or chrome alum both of which must be quite acid to
be effective. Where there is no added acid about 5 grams of sulfite is
sufficient to prevent staining due to carried over developer.
I am not surprized that Paula doesn't like the bisulfite mixture because
it is probably emitting sulfur dioxide, the same stuff that gives hardening
fixers their sharp odor.
No acid it necessary if hardener is not used _and_ the developer is washed
out. A plain water stop is OK provided it is sufficient to wash the developer
out quickly and thoroughly so that it does not continue to work in the fixing
bath. An acid stop will stop the developer but any which carries over into the
fixing bath will tend to react with the thiosulfate.
The conventional acid stop and acid fix prevents a number of troubles but
has a set of vices all its own as does not using them. Alkaline fixing baths
serve no purpose whatever.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
Los Angeles, CA, USA
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