RE: Iron

Ryuji, The edta disodium/sulfite mix has a pH around 6.5 7 if I remember
correctly and the tetra version of the mix is closer to 10. I don't have
those notes handy.

Eric Neilsen Photography
4101 Commerce Street, Suite 9
Dallas, TX 75226
214-827-8301
http://ericneilsenphotography.com
 
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> -----Original Message-----
> From: Ryuji Suzuki [mailto:rs@silvergrain.org]
> Sent: Monday, March 27, 2006 2:06 PM
> To: alt-photo list
> Subject: Re: Iron
>
> I don't have a reference at hand in my office right now, but I
> think
> EDTA is most efficient in complex iron at pH of around 6.
> Depending on
> which salt you are using, the pH may be lower. Addition of
> sulfite or
> KHCA may bring the pH to 6-8 range.
>
>
> In response to others posting lack of fading symptom of VDB
> prints, I
> think there is some misunderstanding of the point. The context
> of
> iron-EDTA thing was deterioration of paper substrate and not
> the image.
> In the iron-gall inked paper I was referring to, the inked area
> is
> destroyed or very easily destroyed with little mechanical
> force.
>
> For the image part, I know hydrogen peroxide at 500-3000ppm
> range is
> enough to bleach out silver image in a matter of days, unless
> the silver
> image is toned. While 500ppm is an artificially high level to
> accelerate
> the testing, peroxide is given off from cardboard, paint,
> adhesive, etc.
> and I personally want to make my images quite resistant to
> peroxide
> attacks. There are environmental oxidants other than peroxide
> as well.
>
> In discussing longevity of images, storage condition is a big
> factor.
> Temp, humidity, etc. If humidity is higher, environmental
> oxidants are
> more easily going into the paper, and the silver is also more
> reactive
> with them. (When you read darkroom cookbook and stuff like
> that, you'll
> see them talking about silver solvent = sodium sulfite, but
> don't forget
> water is a silver solvent as well!) Considering how much PITA
> to keep
> photographic prints in strictly controlled conditions, I think
> it's a
> lot easier to process the material in such a way to minimize
> the
> environmental influence on the image, and ease the
> stroage/display
> condition to more manageable level.
>
>
>
>
> On Mon, 27 Mar 2006 09:27:20 -0800, "Kerik" <kerik@kerik.com>
> said:
> >
> > > I have a good sample of ten year old prints cleared in
> EDTA/sodium
> > > sulfite that look as good as the day they were made. I have
> not
> > > personally seen any EDTA cleared prints that have degraded,
> but by no
> > > means have I seen every
> > > print ever made and cleared with this method.
> >
> > I think the issue may be that EDTA by itself doesn't work
> very well for
> > clearing pt/pd. I've had many comments from workshop students
> who had
> > previously tried EDTA alone and reported such problems, but
> adding sodium
> > sulfite to the mix did the trick. Approx one tablespoon each
> of EDTA and
> > sodium sulfite per liter works well on most papers, as does
> Kodak Hypo
> > Clearing Agent and Heico Permawash.
> >
> > Kerik
Received on Mon Mar 27 16:06:25 2006