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Subject: Photo identification

Photo identification

From: Doug Nishimura <dwnpph>
Date: Wednesday, October 9, 1991
Sue:  I probably can't help you, but maybe you can solve your own
problem.  Certainly identification is difficult without umpteen pages of
descriptions, photos of the object, or (best) the object itself.

1) You have determined for sure that it's silver?  Are there any signs
of typical silver deterioration.  Depending on the age I would be
suspicious if there were no signs unless it had been treated in some way
(gold/platinum, sulfur or selenium toned.)

2)  Are there any unusual characteristics?  (Relief image under raking

3)  Is it definitely a three layer structure (as a 20C gel DOP would

I ask these questions to eliminate the simple answers first.  It is
possible that the image is a red toned silver DOP.  The red could be
from a number of toning processes including metal ferrocyanides -- salts
of copper, cobalt or uranium have been used to produce violet-red to
brown-red tones.  In addition, chromogenic-type dye toners have been
used as well as a number of other dying methods.    It is also possible
that the image is a carbon print made with a bright red pigment.  (We
have such an image in our teaching collection.)  Such an image would
show no image deterioration, but would also have a relief image.  This
process (and the related carbro process) two layer structures -- having
no baryta layer (unlike the 3 layer GDOP.)  Having eliminated these more
common processes we would have to look into less common ones.


                  Conservation DistList Instance 5:23
                Distributed: Saturday, October 12, 1991
                        Message Id: cdl-5-23-002
Received on Wednesday, 9 October, 1991

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