RE: Old Postcard Silver Patina

Bob,

as I know the dichroic fog is a different problem
with similar looking. However there is some
contact between that things. One of the
deterioration factors which can start the silver
degradation is the poor process of the
photograph (e.g. residual thiosulphate
complexes in the layer, etc.).

Because the shadow parts of the picture
contents more silver so this phenomenon is
more intensive on that surface.

If the degradation process started the silver
layer can be visible after a few decades I think
in the case of modern papers mainly on the
RC/PE papers because the soft gelatine and
the missing protective layer...

Bálint

http://archfoto.atspace.com/

Date sent: Sat, 07 Jan 2006 07:36:59 -0400
From: BOB KISS <bobkiss@caribsurf.com>
Subject: RE: Old Postcard Silver Patina
To: alt-photo-process-l@sask.usask.ca
Send reply to: alt-photo-process-l@sask.usask.ca

> DEAR LIST,
> Forgive my "Bobby come lately" entrance into this thread but I just caught
> up on reading my e-mails. Isn't the effect all of you have described
> referred to as "dichroic fog" and is the result of not using an acid stop
> bath (either going from dev straight into fix or using a water rinse w/o
> acetic acid to reduce the pH) and using an acid fixer? It appears that
> there is some reaction that results from putting a print which is still
> alkaline from the developer into an acid fixer. I have been told that this
> isn't a problem when using ammonium thiosulfate fixers which are of a higher
> pH. Ryuji, can you comment on this?
> I have been told by conservators that it isn't visible until after some
> time. I recall seeing some lovely
> 2 1/4 X 3 1/4 contact prints of NYC buildings by Bernice Abbot which had
> this "silvering" in the shadows.
> CHEERS!
> BOB
>
> Please check my website: http://www.bobkiss.com/
>
> -----Original Message-----
> From: fb [mailto:aikus2@freestart.hu]
> Sent: Saturday, January 07, 2006 3:45 AM
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: Old Postcard Silver Patina
>
> Judy,
>
> Some type of toners can conservate the silver
> against degradation (gold, platinum, selenium.
> etc.) The winner (about the opinion of the big
> science) always changing. As I know the latest
> champion the sulphur toner.
>
> Its funny because the sulphur the main silver
> killer and the main guilty in the silver
> degradation crime,
>
> Bálint
>
> Date sent: Sat, 07 Jan 2006 00:08:33 -0500 (EST)
> From: Judy Seigel <jseigel@panix.com>
> Subject: Re: Old Postcard Silver Patina
> To: alt-photo-process-l@sask.usask.ca
> Send reply to: alt-photo-process-l@sask.usask.ca
>
> >
> > For several years I toned most of my prints with a chemical toner that
> > "plated out" silver gelatin emulsion to that silvery look, which I was
> > very very fond of. So naturally when I found (what I called) "plating
> > out" on old photos at flea markets & photo fairs I snapped them up --
> > usually bargains because they were considered "damaged."
> >
> > These were not just, or even primarily, photo post cards, tho some of them
> > too, but all sorts of prints, from a souvenir photo of the Lincoln
> > Memorial mounted on cardboard to A.T. Bartels "Manufacturing Furrier, Fur
> > Garments of All Kinds Made To Order", shown with the staff ranked at the
> > door, undated but with the notation "Mrs. Dan Wolfe, Earlville, Ill."
> >
> > In some, the "white" background has darkened to almost ochre and the
> > silvery part gotten a distinctly blue sheen, for an especially fine
> > effect. To me, removing that patina would be error close to vandalism,
> > though obviously (to quote Johnny Lock) "All men are liable to error; and
> > most men are, in many points, by passion or interest, under temptation to
> > it." (Needless to say, if Locke had been writing in 2004 instead of 1690
> > that would have been "all persons.")
> >
> > In my observation, the patina hasn't changed a lot in maybe 20 years, even
> > a few just propped up on the counter, exposed 24/7 to NYC air -- I suspect
> > the coating isn't all that reactive. I've also seen edges of prints
> > covered by overmats which hadn't patina-ed, & therefore surmise that it
> > didn't happen, or not as readily, in the dark. (The print was under glass,
> > so I figure it wasn't primarily the air.)
> >
> > On the other hand, the "Bartels" print, dark when I got it, has darkened
> > more, losing some of the shine. Tho that could be because it's glued hard
> > & fast onto black card with who knows what for paste.
> >
> > Prints in those boxes of loose prints from the 1930s & later sometimes
> > show the effect, too -- but I find the effect less compelling.
> >
> > Judy
>
Received on Sat Jan 7 11:24:12 2006