Historic use of chalk in Eastern painting

This is in response to James Martin inquiry about historic use of
chalk in Eastern painting (Conservation DistList Instance: 10:29).
In fact I don't know if the following notes may have great
assistance to people working on Eastern painting.

For the last five years, I have been working on Roman wall painting.
I analyzed more than 500 samples of paint and pigments from 14
different sites in Switzerland as well as Pompeii. The samples date
from I to III Century A.D. Among this sum, I analyzed 88 samples of
white paint and raw pigments. The white paint samples cover all the
sites included in the study, while the raw pigments came exclusively
from the house "des Casti Amanti" at Pompeii. Almost a half of the
paint samples analyzed came from motives; the rest came from
backgrounds. At least 50 additional white-pigment-containing samples
(pink, violet, grey and pale yellow or green) were analyzed too.

Prior to this vast project, on Roman wall painting, white pigment
was commonly and wrongly attributed attributed to slaked lime (which
transforms to calcite=calcium carbonate). This wrong attribution was
continuously stated by several searchers despite the indisputable
citations, by Vitruvius and Pliny the Elder, of several natural
white pigments: cerussa, paraetonium, creta, melinum, eretria,etc.
The first analyst to talk about different Roman white pigments was
evidently S. Augusti who was working on Pompeian raw pigments.

>From my own data, of which a great part is not yet published, I can
just say, for the moment, that chalk (in the strict petrographic
sense: a sedimentary calcareous soft rock composed of calcite in the
form of coccoliths and foraminifera) has been widely used by the
Romans for backgrounds, motives and dilution of other pigments. It
seems to be the dominant pigment used in the white backgrounds
(other white pigments such as aragonite or dolomite were still in
use). However, the use of slaked lime is attested in lower quality
painting. Chalk was also a dominant white pigment for dilutions
(especially of the yellow and the green as well as the preparation
of the pink); other pigments were also used. In the motives, chalk
seems to be the second white pigment in use after aragonite. Its use
is commonly attested in lower quality painting. While other pigments
(aragonite, dolomite, cerussite and diatomite) are generally
detected in rich paintings in association with expensive pigments
such as gold leaf, vermilion, purple, Egyptian blue, minium (red
lead), etc.

In this context, I would like to [ask] Mr Martin about the age of the
Eastern painting where chalk was detected and if it may coincide
with the Roman Period. I also appreciate receiving further
information about these paintings and it would be possible to
continue our discussion out of the DistList.

P.S.: a first publication of my results concerning the white
pigments will appear in the "Proceedings of he International
Workshop on Roman Wall Painting: Materials, techniques, Analysis and
Conservation" that I organized at Fribourg, 7-9 March 1996. This
volume (of which I am the first editor) will appear before the end
of this year.

Hamdallah Bearat, PhD, DEA, B.Sc
Senior Research Officer (Assistant Professor)
Institute of Mineralogy and Petrography
Fribourg University, Perolles
CH-1700 Fribourg
+41 37 29 89 31
Fax: +41 37 29 97 65

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                  Conservation DistList Instance 10:32
                Distributed: Friday, September 27, 1996
                       Message Id: cdl-10-32-001
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