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Subject: Oddy test

Oddy test

From: Barbara Appelbaum <aandh>
Date: Wednesday, March 7, 2001
Agnes Gall-Ortlik <agaor [at] caramail__com> writes

>I am carrying out Oddy tests on gap-filling materials for enamels on
>metal. I have found some references in the literature describing the
>directions for setting up the test, but of those, just one gives
>information on how to evaluate and interpret the results--color
>shift, surface condition, localization and morphology and changes:
>I would be thankful for any answer that would enable me to improve
>interpretation clues.

It was my impression that the point of the Oddy test was to have a
quick-and-dirty way to characterize the nature of the off-gassing
from materials that will be used for exhibition, not to help choose
conservation treatment materials.  With some materials, off-gassing
is an indication of the long-term aging characteristics that are a
concern for treatment materials, but not necessarily.

The best way to pick treatment materials is to be creative in using
the few materials that have been proven by research and a long
history of use to be stable over long periods of time.  There are
several articles published in the last few years on filling
materials created from polyvinyl acetate resin or Acryloid B-72 with
a variety of fillers including glass microballoons, cellulose
powder, and fumed silica, with pigments added as necessary.  These
can be combined to produce fillers of different consistencies,
hardnesses, etc.  I do not work on enamels, but perhaps those who
treat such things (and other things with similar properties, like
porcelain) can be encouraged to come up with their favorite recipes.
Some people love microballoons and others absolutely hate them, but
a willingness to experiment with techniques and recipes is necessary
in any case.  Commercial formulations may be easier to use straight
out of the jar, but their contents are always questionable.

B. Appelbaum

                  Conservation DistList Instance 14:48
                 Distributed: Thursday, March 22, 2001
                       Message Id: cdl-14-48-002
Received on Wednesday, 7 March, 2001

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