Re: Sodium Bisulfite

Hi Katharine,
I assume the sodium bisulfite is on a 12% concentration.
How much time you put the picture in the bath?
An the you bath it again in a water bath, for how long?
What about stubborn cases? You keep it longer?
Let me give you a recent example of what happened to me:
I was working on a full color print, this picture has an open clean white
sky therefore the negative section of the sky is totally black.
I did my first cyano print and everything was fine (sorry I sized the day
before first with gelatin and glyoxal).
I go next day for my Blue channel and yellow pigment and the sky comes out
"yellow", I thought it was stained, next day I did my Green channel and
magenta pigment and I got a beautiful picture but with the yellow sky (as I
said out of a black negative).
I wash it with sodium bisulfite and the stain is still there.
Yes, I know I can create a new negative and paint the sky on white but I
want to know what may have happened.
Thanks,
Giovanni
----- Original Message -----
Wrom: ZRCLBDXRQBGJSNBOHMKHJYFMYXOEAIJJPHSCRTNHG
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, August 21, 2004 12:13 PM
Subject: Re: Sodium Bisulfite

> Martin Angerman wrote:
> >
> > The sulfite acts as a reducing agent. It clears the dichromate by
reducing
> > it to an inactive form.
>
> Hmm. I've always wondered just what a clearing agent does, chemically,
> but this explanation doesn't work very well for me, since what is called
> "dichromate stain" in my experience almost always consists of Cr+3 not
> Cr+6. I tried a few years ago to introduce a new name here for the stain
> to reflect this reality, but had little luck with this campaign and gave
> it up after a while.
>
> Except for unusual cases where a peculiar combination of sizing and/or
> paper hangs onto the bright yellow dichromate and won't let it go, the
> hexavalent dichromate, being very soluble, almost invariably washes out
> in the developing water without additional clearing needed. It's the
> less soluble reduced chromium species that comprise a tan, brown, or
> green stain that must be removed to clear the print. I don't know what
> the clearing agent does to the reduced chromium to get rid of it, but
> the point is that the chromium in the stain is already reduced before
> the clearing agent is introduced, and that we've just confused ourselves
> by calling this reduced-chromium stain a "dichromate stain."
>
> It's true that the same clearing agent works for both the less typical
> dichromate stain and the usual reduced-chromium stain, (except for very
> heavily overexposed prints that are so stained that sulfuric acid may be
> needed to clear them) but I'm not sure what that means in terms of what
> happens chemically.
>
> At any rate, my own experience is that sodium bisulfite can be re-used
> many times without diminishing its effectiveness. I had a gallon of it
> mixed up years ago that I used for 3 or 4 years before it stopped
> working. I only need to clear very occasionally, so the number of
> prints that were cleared with that gallon over the 3 or 4 years was
> rather small, perhaps 12 or 15 at the most, but it would have been a
> waste of materials and money to mix up new stuff each time, when the old
> stuff was fine for re-use.
>
> You know you need a new batch when the solution loses its pungency of
> odor; in my experience that happens comcomitantly with loss of ability
> to clear effectively.
>
> I no longer keep a big jug of clearing agent around, because I've
> learned that immersing the paper in the clearing bath is only necessary
> in odd cases such as the sizing/paper problem mentioned above or when
> I've accidentally spilled some dichromate on the coating table and not
> noticed it and it's soaked into the back of a piece of paper. But for
> simply clearing an image, I've found that simply brushing the clearing
> agent on the image works well, and then a short dip in water is all
> that's needed to rinse it out of the print, whereas when the paper is
> immersed, you need a more extended soak to make sure you've got the
> stuff out of the paper. So now I just keep a pint mixed instead of a
> gallon, but that pint is as fresh and effective today as it was when I
> mixed it months ago; the extra air in the liter bottle that I keep it in
> doesn't seem to affect it at all.
>
> Katharine Thayer
>
>
>
> >
> > Air can also oxidize sulfite to sulfate, ruining it as a clearing agent.
> > Therefore, I would not recommend storing it for more than a day. Going
from
> > Saturday to Sunday would probably be OK, however.
> >
> > My thoughts would be similar to reusing glyoxal and over-using fixer.
The
> > sulfite (and others) are relatively cheap, particularly compared to your
> > time and other materials. How many people would dilute platinum salts
or
> > short a mixture of good pigment in gum printing, just to save money?
The
> > same applies to the rest of the process.
> > ----- Original Message -----
> > Wrom: SWZIDREXCAXZOWCONEUQZAAFXISHJEXXIM
> > To: "AltPhoto" <alt-photo-process-l@sask.usask.ca>
> > Sent: Saturday, August 21, 2004 7:06 AM
> > Subject: Sodium Bisulfite
> >
> > > After clearing a 2 or 3 gum prints, is the sodium bisulfite solution
> > > storable for later use or should I just dump it and make a new
solution
> > > when needed? Thanks.
> > >
> > >
> > > Darryl M. Gage
> > > Forestville, NY
> > >
> > > "Strange and beautiful are the stars tonight..." Blue Rodeo
> > >
> > >
>
Received on Tue Aug 24 10:52:41 2004