Re: Sodium Bisulfite

Giovanni,
     If the print is not dried first, it is more tender. Once it is dry it
is hard to scratch or wreck. The clearing bath softens the gum enough to
make it susceptible to scratching or sloughing off..
     Yes, you can use sodium sulfite, from a 5%-10% solution. The reason
why potassium metabisulfite is recommended the most is it is very water
soluble and thus requires shorter wash times afterwards for archival
purposes--10 minutes as opposed to 20-30 or more.
Chris
----- Original Message -----
From: <gdimase@hotmail.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, August 24, 2004 7:18 PM
Subject: Re: Sodium Bisulfite

> You mean if the print dries totally the clearing process will not work?
> Giovanni
>
> ----- Original Message -----
> Wrom: UZXUWLSZLKBRNVWWCUFPEGAUTFJMVRES
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Tuesday, August 24, 2004 5:56 PM
> Subject: RE: Sodium Bisulfite
>
>
> > Why Sodium Bisuphite? I always use Potassium Metabisulphate - the stain
> > goes away in a few moments in most cases -the only trouble I ever had
> > was not letting the prints dry before clearing.
> > Kate
> >
> > -----Original Message-----
> > Wrom: KPNKMBIPBARHDMNNSKVFVWRKJVZCMHVIBGDADRZFSQHYUCDDJ
> > Sent: Wednesday, 25 August 2004 4:50 a.m.
> > To: alt-photo-process-l@sask.usask.ca
> > Subject: 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
> > > > >
> > > > >
> > >
> >
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Received on Tue Aug 24 19:35:28 2004