Re: Old Postcard Silver Patina

Bálint,

Thanks for these references, they are very interesting.

They also seem to address mostly silver gelatin glass
negatives. This effect happens also on positives (as in
the example that started this thread) and has probably
the same origin.

But I have never seen it on albumin positives. Or perhaps
I just missed it, I don't know ... Could it be that the bond
between the silver grains and albumin is stronger and
doesn't allow migration?

Tom Sobota
Madrid, Spain

At 12:45 06/01/2006, you wrote:

>Jesper Stub Johnson: Chemical treatment of black-and-white
>negatives, S. 191\u2013196 > pdf (7100 KB)
>http://palimpsest.stanford.edu/iada/ta91_191.pdf
>
>Klaus B. HENDRIKS: THE PRESERVATION AND
>RESTORATION OF PHOTOGRAPHIC MATERIALS IN
>ARCHIVES...Paris, January 1984 pp45-46.
>http://unesdoc.unesco.org/images/0005/000586/058641e.pdf
>
>Di Pietro, Giovanna Silver mirroring on silver gelatin glass
>negatives Diss. phil.-nat., 2002 (2'134 KB)
>http://www.unibas.ch/diss/2002/DissB_6232.pdf
>http://sul-server-2.stanford.edu/byauth/dipietro/mirroring/
>
>
>Bálint Flesch
>
>http://archfoto.atspace.com/
>
>
> >
> > > It looks to me like typical "mirroring" from oxidation of
> > > the image silver. The silver is converted to silver oxide by
> > > polutants in the air. Some of this oxide migrates to the
> > > surface of the emulsion and some is converted back to silver
> > > by other polutants.
> > * * *
> > > There are ways of removing the silver and silver oxide
> > > from the surface but they carry a risk of destroying the
> > > original image and there will be some fading of the original
> > > image beause some of the silver is gone.
> >
> > Some "aggressive conservators" have reported good results with
> > bleach-and-redevelop protocols, but it takes fortitude to put a valuable
> > old photo through that. I did it with a St. Ansel owned by a friend and we
> > were both pleased with the results. It definitely eliminated the mirroring
> > without losing density. YMMV.
> >
Received on Sat Jan 7 04:22:54 2006