MEDIUMS AND ADHESIVES 73
also, to give a uniform surface to the work. As the variety of resins increased,
during antiquity, and as the differences among them were recognized, it became
necessary to make distinctions. At one time amber and other hard resins had been
called * berenice* By the XIV century Italian writers referred to resin as vernix
and to the varnish as vernice liquida. It has been suggested that the origin of the
name is based on the story of Queen Berenice of Cyrene whose golden, or amber-
colored hair was accepted by Venus as a thank offering for the safe return of the
Queen's husband, and was transformed by the goddess into what is now known
as the Milky Way. Laurie offers a less romantic suggestion: that the name came
from that of sandarac resin which was formerly called * berenicej being exported
from Berenice on the African coast. In any event, the name, varnish, came from
such a word.
There are two kinds of varnish in common use: the simplest consists of a solu-
tion of a resin in a volatile solvent; the second is made of a resin dissolved in a
drying oil to which a thinner is generally added. The spirit varnishes are of a soft
resin, such as mastic or sandarac, dissolved in turpentine or in alcohol; they are
brittle and not very durable. An oil varnish in modern manufacture is made by
heating a hard resin, such as a copal, and then dissolving it in linseed oil, with or
without tung oil. The harder the resin, the higher is the temperature to which it
must be heated. The mixture is thinned with turpentine or with alcohol. Lead
and manganese compounds are often incorporated in the oil before or after the
addition of the thinner. Such a varnish is apt to be too dark and too insoluble for
use with pictures. Spirit varnishes, being readily soluble in alcohol, are easily
removed from the surface of a painting. Oil varnishes require special methods,
depending on the nature of the resin and on the properties of the ingredients.
Vegetable Oils are oils occurring in the vegetable kingdom (see Oils and Fats).
Vegetable Waxes (see also Waxes and Animal Waxes). These make up a large
class, in which the typical member is carnauba wax. The only other commercially
important member is candelilla. Vegetable waxes are generally found in or upon
the outer skin of leaves, stems, flowers, and fruit, and, also, to some extent, in the
tissues. They contain, as a rule, hydrocarbons of the paraffin series, C«H2n+2,
where * n' ranges frequently from about 30 to 60, alcohols of the phytosterol
series, either free or combined with fatty acids, and the higher aliphatic alcohols
of the type of ceryl alcohol, or those of higher carbon content, again either free or
in combination with fatty acids (see Hilditch, p. 127).
Vehicle is a traditional term used interchangeably with ' medium * as a name
for the film-forming or binding material of paint (see also Medium).
Venice Turpentine (see also Balsam). This balsam is produced by the Euro-
pean larch, Larix decidua, and is collected chiefly in the Tyrol. It is a viscous,
sticky substance with a characteristic pinaceous odor. It consists of about 63
per cent of resinous acids, 20 per cent of terpenes, and 14 per cent of resins; it is
free from crystals of abietic acid which discolor the common turpentines. Unlike