Re: Who put the Glaze on Weston's Pepper?

imagwkrs@midcoast.com
Wed, 20 Mar 1996 10:29:59 -0500

...to wit from Jim Reilly's tome* on the preservation & conservation of
photographs, this information is directly applicable to early 20th-Century
gelatin-silver images, and in time will probably be true of gelatin-silver
images produced today, and in the future.(Our current storage concerns may,
however, alleviate some of the potential future mirroring.)

(quote)"SILVER MIRRORING: Shiny, bluish silver mirroring is so
characteristic of gelatin developing out prints and all other kinds of
filamentary-silver-in-gelatin images that it is a useful clue in
identifying them. Nearly all 19th. Century gelatin-developing-out paper
prints have some mirroring as a consequence of oxidation-reductive
deterioration. In this process, silvcer ions migrate to the extreme
uppermost surface of the gelatin layer and are reduced back to the metallic
state to form an almost continuous layer of small, tightly packed
particles. (Ordinary glass mirrors are made by the controlled reduction of
silver ions onto a glass surface.) The conditions which cause mirroring in
some faded silver prints and not in others is not completely understood."

More detailed information is then discussed pertaining to the formation of
the silvering, such as, "If a print is only partially protected from air
and moisture (for example, by a smaller object placed on it during
long-term storage), the mirroring will occur everywhere but under the
object, and it will trace the objects outline in bluish sheen. Mirroring
often occurs directly over areas where a hydroscopic adhesive was used."

Jim closes with, "Mirroring should not be removed from gelatin prints by
abrasion or chemical treatment. Special care should be taken not to touch
the surface of mirrored prints, because finger oils will cause changes in
the surface."

..and Judy, I wouldn't worry about your images, vintage and contemporary,
if they hold up as well as MANY in albums from Mongegan Island that I'm
preserving & conserving right now, they will be fine. Many of the images
are 80-100 years old, well mirrored, very stable, and still beautiful!

* REILLY, James M. _Care and Identification of 19th-Century Photogaphic
prints_, Eastman Kodak Company, 1986, page 47. ISBN 0-87985-365-4

Roderick Hook
PhotoArchivist & Conservator