Re: Old Postcard Silver Patina

From: Michael Koch-Schulte ^lt;mkochsch@shaw.ca>
Date: 01/04/06-11:00:41 PM Z
Message-id: <011b01c611b4$fb4caed0$0100a8c0@TRASHO>

Thank you Richard. Definitely "mirroring" would be an apt term if I had to
give it a name. Does anyone know -- being that the photo was produce at the
turn of the century -- would this be a silver gelatin emulsion already or
were they still using salts and albumen? This one has a definite crack on
the emulsion (top, right). It was produced on card stock with a pre-printed
postcard form on the back. A "one-off" I'm guessing or maybe a short run of
25 or 50 probably so the person could mail it off to relatives or friends.
Any ideas on how and what equipment these cards were produced? Was this a
rapid turn around business?

~m

----- Original Message -----
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, January 04, 2006 10:16 PM
Subject: Re: Old Postcard Silver Patina

>
> ----- Original Message -----
> From: "Michael Koch-Schulte" <mkochsch@shaw.ca>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Wednesday, January 04, 2006 7:53 PM
> Subject: Old Postcard Silver Patina
>
>
> > I'm trying to identify the patina that is on the surface
> > of this old
> > photo-postcard. It looks to me like (and probably is)
> > silver when held to
> > the light at an angle. What would cause this? Bad fixing?
> > Could it have been
> > deliberate? The card dates between 1910 up to the first
> > world war. Purchased
> > recently in a market in Zagreb for $1. There is a mark on
> > the centre right
> > which shows the original black tones. Possibly a scuff. Is
> > it
> > possible/advisable to clean the silver off this card? Is
> > it possible to
> > stabilize the image using modern stabilizers? Thx. Any
> > history on
> > photo-postcards would also be appreciated.
> >
> > ~m
> >
> > http://www.mondotrasho.ca/pages/alt-photo/cards/Postcard.jpg
> >
>
> 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. Oxidation is not a sign of poor
> processing, in fact a very small residue of hypo has been
> shown to prevent oxidation to some extent. It is the result
> of oxidizing gasses, often peroxides, present in the air.
> 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.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
>
Received on Wed Jan 4 23:00:54 2006

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