From: Christina Z. Anderson (zphoto@montana.net)
Date: 07/01/03-11:25:15 AM Z
Hi Bill,
Sodium sulfite, when I have seen it (not often), is used at a 10%
dilution. This would be a little over 4T per liter. I came across a mention
in an old book that if you just leave the print outside it'l bleach the
dichromate too (?) but anyway, haven't tried that, because it seems so
weird to me that sunlight would clear it away if it makes it dark! Pot
metabi I use at a 1% dilution as per Livick but a lot of people use it at
the 5% strength: 2 Teaspoons (or a little over 3 Tablespoons for the 5%)
per liter. If you dip a test strip into it, it clears really quickly,
almost immediately, but the recommendation is to leave it in for 25% longer
than it takes to look clear--probably should take a minute or two. If you
want to get rid of the brown dichromate borders that are totally overexposed
you would have to leave it in waaaay longer. I acccidentally left my test
print in it overnight and no more brown dichcromate borders, but that is not
a good idea because it softens the print too much and you might lose your
image :)
Chris
----- Original Message -----
From: "The Painted Horse" <paintedhorse@in-tch.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, July 01, 2003 11:32 AM
Subject: Re: Clearing gum's color
> Thank you Chris.
> I'll pick up some pot metabi and give it a try. The sodium sulfite,
> though disolving rather easliy, didn't seem to do much in the way of
> clearing the color. I used it at 5% strength which was the amount
> suggested for the alum, metabisulfite, and sodium bisulfite. Duration
> was around 20 minutes (there were no time guidelines in the literature I
> have). Is this an approximate percentage for the use of pot metabi?
> Should I have washed it much longer?
> Bill-
>
> "Christina Z. Anderson" wrote:
> >
> > Bill,
> > Short answer: yes it can clear.
> > Long answer: sodium sulfite doesn't seem to dissolve as well as
pot
> > metabi, and if I remember correctly this greater solubility of pot
metabi
> > decreases your wash times after clearing so that's why it is preferred,
> > aside from the fact (if I am remembering correctly) that pot metabi is
less
> > damaging to your gum emulsion than other methods of clearing.
> > People use all kinds of clears: alum, the sulfites, sulfuric acid,
> > sodium hydroxide (red devil lye), hydrochloric acid (muriatic). The
> > stronger ones get rid of the green chromic stain due to overexposure.
> > Now I have GOT to get off the computer and get a life...
> > Chris
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