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Subject: Foxing on photographs

Foxing on photographs

From: Doug Nishimura <dwnpph>
Date: Saturday, September 7, 1996
Re: Chemical Restoration of Albumen Prints

Just a short comment with regard to Klaus Pollmeier's comment about
chemical restoration of albumen prints (written in response to
Norman Laurila's question about albums with foxing). In addition to
the problem of not necessarily recreating what the original
photographer intended (in terms of tone-range, contrast and image
tone), POP images have the additional problem of not generally
working with conventional bleach and redevelopment. I worked with
the late Dr. Hendriks for several years on this problem (he worked
on the problem for about eight years) and the problem with POP
images is that they are composed of photolytic silver--small spheres
of silver created by light. After bleaching out such an image there
is simply no nucleation centers for redevelopment to use to
"reconsolidate" the silver image. The photos bleach very well, but
you won't get any image back. Electron micrographs showed a fairly
nice even dispersion of tiny silver particles that were so small
that they didn't do much of anything in terms of blocking light. For
this same reason, DOP images that are too badly faded can't be
"restored" by bleach and redevelopment nor can a decent copy
negative be created by neutron activation autoradiography. One of my
colleagues worked out a system in which chlor-auric acid was used as
the bleaching agent and this worked for POP images. The problem with
this method is, again, the issue of changing the tone, tone-range,
contrast as well as altering the metal content of the image.

-Douglas Nishimura
Image Permanence Institute

                                  ***
                  Conservation DistList Instance 10:26
                Distributed: Tuesday, September 10, 1996
                       Message Id: cdl-10-26-001
                                  ***
Received on Saturday, 7 September, 1996

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