Colour matching

Srebrenka Bogovic-Zeskoski <fineartinfo [at] rogers__com> writes

>... It is an abstract painting and the damage
>is mostly in a large area of yellow-orange colour.
>
>Inpainting this hue has proven to be more than challenging, almost
>impossible, hence this plea for suggestions and advice. The
>touch-ups, like a chameleon, change the hue quite substantially in
>different lights.  If the match is perfect in daylight it is much
>darker under an incandescent and/or halogen light source.  I presume
>that I am dealing with a "metameric match" and/or pigment-size
>(Rayleigh scattering) since both yellow and orange are cadmium based
>pigments. The issue presents itself when using any medium: oil,
>acrylic or water color

Based on your description of "changing colors" I advise you test for
a mars pigment. This class of pigments is chameleon like in
appearance especially as it ages or is touched by fingers, hand,
etc., or if applied unevenly. If you have a mars pigment you must
find out what color you have and then use it along with the cadmium
you say that you have. Your best chance at matching is to work with
clean areas of the original and use the exact pigments that are
there and in the exact proportion. Try using a water based medium as
it is less problematic and is easily removed until the right result
is achieved.

Richard J. Trela
Trela Fine Art Conservation, Texas


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                  Conservation DistList Instance 24:5
                   Distributed: Friday, June 18, 2010
                        Message Id: cdl-24-5-004
                                  ***