Chemistry Reference
In-Depth Information
shaped, either by carving and polishing its surface or by heating, since it
softens (at about 150°C) and can then be molded. Because it is easy to shape,
amber has been used, since early prehistoric times, for making ornamental
and decorative objects such as beads, amulets, and boxes. Moreover, as it
dissolves in some vegetable oils, amber has also been used as a binder in the
preparation of varnishes. One of the oldest and best known sources of amber
is the Baltic Sea coast of Germany, but there are also rich deposits off the
coasts of Sicily and England in Europe, in Myanmar (Burma) in Asia and in
the Dominican Republic and Mexico in the Western Hemisphere. The prove-
nance of archaeological amber has been extensively studied using a variety
of physical methods (Lambert et al. 1996; Beck 1970).
Rosin.
Rosin
resin, also known as
colophony
, is collected from one of over
100 different types of trees that grow throughout Europe, Asia, North
America, and New Zealand. The term
colophony
seems to derive from the
ancient city of Colophon, in Lydia, which produced a high-quality resin.
Rosin is drawn directly from living trees in a tapping process that entails
inducing outflow of the resin from the trees. Rosin has been used as an
adhe-
sive
and
size
and in the preparation of
paints
.
Mastic.
Mastic
is the resin obtained from the small mastic tree
Pistacia lentis-
cus
, of the sumac family, found chiefly in Mediterranean countries. When the
bark of the tree is injured, the resin exudes as drops. Mastic is transparent
and pale yellow to green in color. The main ancient uses of mastic were as
an
adhesive
, for making
varnish
, as a
medicine
, and for
flavoring
.
Dragon's Blood.
Dragon's blood
, a red resin described by Dioscorides, the
Greek botanist from the first century C.E. and by other early writers, was
derived from a number of different plants. A main source of the resin seems
to have been
Dracaena cinnabari
, a tree of the agave family, from which it is
exuded as garnet colored drops when the trunk or branches of the tree are
injured. The early Greeks and Romans believed dragon's blood to have
medicinal properties. Its main use in the ancient past, however, was as a col-
oring material and, since the end of the eighteenth century Italian crafters
used it as a varnish for violins.
Shellac.
Shellac
is outstanding in that it is the only resin of animal origin.
Shellac is a yellow, orange, or brown solid derived from
lac
, the secretion of
the scale-like
Kerria lacca
insects that inhabit trees in areas of India and Thai-
land. To obtain the resin, twigs encrusted with the insect's secretion are cut
down from the trees, the incrustation is removed from the twigs, coarsely
