Re: !!!!!!!!!!! PEROXIDE !!!!!!!!!!!!!

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From: Judy Seigel (jseigel@panix.com)
Date: 03/01/02-10:24:51 PM Z


On Fri, 1 Mar 2002, Christina Z. Anderson wrote:
> The bleach/etch formula basically eats away the dark areas of the print
> and then etches the highlights, so that if all the gelatin is rubbed off it
> will redevelop into a negative image, with the possibility of leaving stuff
> unrubbed and therefore having a positive image or part positive/part
> negative. If it is not strongly acid, the dissolution of the gelatin will
> not happen. I have not read of any other metal salts working. However, I

I don't know (or don't remember) WHY it happens, but WHAT happens is that
this formula DESTROYS metallic silver. The black part of the print is
metallic silver, so it gets destroyed. If print hasn't been fixed yet, the
silver HALIDE (which is not METALLIC) remains, so it can then be exposed
and developed -- ergo (that's Latin !), a reverse print.

I figure that when the silver is destroyed the gelatin in, over, or around
it also gets destroyed, right down to the paper base if you wish to rub a
bit... hence a relief effect: part with & part without gelatin.

best,

Judy

> have only found about 9 or 10 sources that even mention the process. I can
> send you some info offlist if you would like...attachment file.
> Chris
>
> > Dear All,
> >
> > I've been using an etch-bleach bath of peroxide and cupic chloride.
> > Anyone have any idea how it works? Might other metal salts be effective?
> > Are there other etch-bleach baths that, like this one, attack the gelatin
> of
> > the emulsion itself?
> >
> > Robert Schaller
> >
> > on 2/27/01 9:03 PM, Judy Seigel at jseigel@panix.com wrote:
> >
> > >
> > >
> > > On Tue, 27 Feb 2001, Jeffrey D. Mathias wrote:
> > >> ... However, hydrogen peroxide is also
> > >> sometimes used as a contrast agent with some alt-process coatings, and
> > >> in this use accurate knowledge of the solution strength is required for
> > >> consistent results.
> > >
> > >
> > > Well that figures... Only one I've heard of, BTW, is for some pt/pd
> > > coatings. Are there others?
> > >
> > > Judy
> > >
> > >
> >
>
>


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