P3D Re: (fwd) Re: Copying old photographs!!!!

[Bob Wier <wier@xxxxxxxxxxxxxxxxx>]

Here's an interesting message from another list I'm on, which
bears on antique stereo views as well...

--BW


|From: Steve Knoblock <knoblock@xxxxxxxxxxxxxxxx>
|Subject: Re: (fwd) Re: Copying old photographs!!!!
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|With regard to albumen-silver images, although properly processed, the
|albumen forms an "unfixable" silver-protein compound in all areas of the
|print after processing, making it unique among photographic binders. The
|albumen reacts with silver ions, for which it has a high affinity, forming
|the silver-protein compound. Part of the silver associated with albumen
|during sensitizing is not removed when fixed and remains as colorless
|silver albumenate.
|[Reilly, Care and Identification of Nineteenth Century Photographic Prints,
|p. 27]
|
|Note that this process occurs *during sensitization* and is not the product
|of poor fixing or washing. The presence of the colorless protein-bound
|silver does set the stage for deterioration if the print was not washed
|properly. If reactive sulfur is present the silver-protein material will be
|converted to yellow silver sulfide, responsible for yellowing in the
|non-image areas. It still requires a poorly processed print, with about 15%
|attributable to poor processing out of all albumen prints exhibiting
|deterioration.
|
|I agree that gelatin-silver images are less prone to photochemical
|deterioration, as you point out. I would not be overly concerned in
|scanning modern gelatin-silver photographs. It's the albumen prints I worry
|about being harmed by scanning, although the risk varies with the
|individual print.
|
|Steve
|
|>> But not all of the silver in a 'silver image' is 'metallic silver'.  It
|>> changes over time, as well.  Some part of the silver in properly
|>> processed and washed 'silver image' is ionized, and is unstable.
|>
|>If it is properly fixed and washed, this should be an *exceedingly*
|>small percentage.
|[snip]
|>In the absense of such evidence, I think it's a bit alarmist to imply
|>that one is somehow irresponsible in scanning or copying such photos.
|
|   _/ Steve Knoblock                      mailto:editor@xxxxxxxxxxxxxxxx
|   _/ City Gallery                            http://www.city-gallery.com/
|   _/ Member NSA               http://www.3d-web.com/nsa/nsa.htm
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|--- end forwarded text



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