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rather indiscriminately to woods having a certain fragrant odor characteristic of
the true cedars. The cedar of Lebanon (Cedrus Libani}y one of the important
woods of history, was used widely in Egypt and the Near East. No true cedar is
indigenous to Europe. The wood is generally reddish brown and light in weight,
but has a coarse and spongy texture; it is easy to work but is liable to shrink and
warp. The annual rings are clearly marked. According to available records, it was
one of the woods used for the support of murnmy portraits made in the Fayum
district between the I century B.C. and the VI century A.D. It had occasional
use in the panels of European painting.
Chestnut (Casfanea). The sweet chestnut (C. vulgarls) is commonly known in
Europe. A similar tree (C. dentata), before a recent blight, flourished in America.
Chestnut resembles oak and it is mainly the indistinctness of the medullary rays
that differentiates it from that wood. It is a soft, light wood, comparatively free
from warping and shrinking. It is ring-porous and hence the annual rings are
easily distinguishable. Spring-wood vessels (pores) are large and generally arranged
in double or triple rows; summer-wood vessels are very small and can scarcely be
observed with the naked eye. Because of the large pores, plain-sawed chestnut has
a conspicuous figure. It is subject to attack by worms. Chestnut was much used
for painted panels, particularly in Italy (see also Wood).
Clay is perhaps the oldest of plastering materials. Although one of the poorest,
it has endured surprisingly well as a paint support in certain instances. The
essential components of clay are the hydrous silicates of aluminum which are
widely distributed on the earth's surface. These may be associated with other
substances or Impurities to a greater or less extent. Clay absorbs water readily
and becomes plastic* a propertv which has made it pre-eminently useful in the
ceramic arts.
Cloth, (see also Fabrics). Although this term might have become general for
the woven stuff that is used, in various kinds, as a support for paint, * canvas ' or
* fabric' are more apt to be applied to it. The word c cloth' is frequently used,
however, in this general sense. More specifically it is used to define a kind of weave:
simple cloth, in which warp threads and weft threads pass over and under each
other alternately; and, among others, compound cloth in which there are multiple
warps or wefts, or both, one warp and one weft being of cloth weave.
Copper. The chemical element, copper, is a yellowish red, soft metal. It is
ductile and malleable and, hence, is easily rolled into thin sheets or plates. It is
prepared by the reduction of sulphide, oxide, and carbonate ores. Most of the cop-
per that now appears in the market is electrolytically refined; its purity generally
runs better than 99.9 per cent. The electrolytic refining of this metal was first
carried out on an industrial scale in 1869 at Pembrey, Wales.
Freshly-worked copper has a luster and takes a bright polish but it is soon
tarnished when exposed to the air. Under indoor conditions, it is stable for
centuries and the tarnish remains very superficial. Exposed out-of-doors, it