Those among the colours which require a dry, cretaceous,
coating,[1] and refuse to adhere to a wet surface, are purpurissum,
indicum, cæruleum,[2] melinum, orpiment, appianum, and
ceruse. Wax, too, is stained with all these colouring substances
for encaustic painting;[3] a process which does not admit of
1.
2.
3. Cerœ,'
or 'waxes,' was the ordinary term for painters' colours among the Romans,
but more especially encaustic colours, which were probably kept dry
in boxes, and the wet brush or pencil was rubbed upon them when colour
was required, or they were moistened by the artist previous to commencing
work. From the term 'ceræ' it would appear that wax constituted the
principal ingredient in the colouring vehicle used; but this does not necessarily
follow, and it is very improbable that it did; there must have
been a great portion of gum or resin in the colours, or they could not have
hardened. Wax was undoubtedly a most essential ingredient, since it
apparently prevents the colours from cracking. 'Ceræ' therefore might
originally simply mean colours which contained wax, in contradistinction
to those which did not; but was afterwards applied generally by the Romans
to the colours of painters."—Wornum, Smith's Diet. Antiq. Art.
Painting.
4.