Historic use of chalk in Eastern painting

This inquiry relates to a current investigation of materials used in
Eastern painting; specifically, the use of chalk (calcium carbonate
as characterized by morphology and the presence of coccoliths) as a
primary pigment, rather than an inert pigment.  Western conservation
literature cites the use of another form of calcium carbonate, shell
white (or gofun), in Japanese painting, but is rather quiet on the
use of chalk as a primary pigment in the East, or for that matter in
the West

I stress the use of *chalk* as a primary pigment.  Chalk has been
identified as a minor component in paint and ground layers in
Eastern objects, so we might reasonably infer that there is a
geological source in the region.  Moreover, if an indigenous source
was not known or exploited, it is possible that chalk was available
through trade with the West.

I would like to hear from anyone who can provide documentary sources
on this topic (e.g., literature references, analytical reports,
etc.).  For those of you who are still reading this posting, I'll
provide some additional information about the case at hand.

Analysis of samples of paint and ground from a figurative painting
on linen showed the presence of chalk in white and colored paint
layers.  Calcium carbonate was identified visually by polarized
light microscopy (PLM), and was confirmed using infrared
microspectroscopy (IMS).  PLM observation of coccoliths indicated
the presence of chalk.  Lath-shaped particles typical of shell white
were not observed in the samples, and the infrared spectra did not
indicate the presence of aragonite, a component of shell materials.
Rather, IMS, and SEM-EDS which showed the presence of major Ca and
Mg, suggested the presence of dolomite in the samples.  X-ray
diffraction has not been performed.  IMS also indicated the presence
of a secondary amide (protein) in the samples, suggesting a protein
binder.  Other pigments identified in the paint samples analyzed are
smalt, malachite, azurite, and red lead.

Thanks for your assistance,

James Martin
Director of Analytical Services and Research
Associate Conservator of Paintings
Williamstown Art Conservation Center

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                  Conservation DistList Instance 10:29
                Distributed: Friday, September 20, 1996
                       Message Id: cdl-10-29-003
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