White Chalk
:
ON THE PRIMARY, YELLOW.
Is a well-known native carbonate of lime, employed by the artist only as
a crayon, or for tracing his designs, for which purpose it is sawed into
suitable lengths. White crayons and tracing chalks, to be good, must
work and cut free from grit. From this material are prepared whitening
and lime, which form the bases of many cheap pigments and colours, used
in distemper, paper-staining, &c.
Besides those me
tioned, there are other metallic whites varying in
beauty and opacity, such as those of mercury, arsenic, and antimony; but
none of them are of any value or reputation in painting, on account of
their great disposition to change of colour, whether by light or foul
air, both in water and oil.
There are also other terrene whites, under equivocal names, among which
are Morat or Modan white, Spanish white, Troys or Troy white, Rouen
white, China white, and Satin white; the latter being a sulphate of lime
and alumina, which dries with a glossy surface. The common oyster-shell
contains a soft white in its thick part, and there is the white of
egg-shells. There is, too, an endless variety of native earths, in
addition to those prepared by art. The whole of them, however, are
destitute of body in oil; and several, owing to their alkaline nature,
are injurious to many colours in water, as well as to all colours which
cannot be employed in fresco.
Among the infinitude of white substances, the artist finds that there
are but three white pigments--those of lead, zinc, and baryta. The first
possesses the greatest opacity, while the second and third are most
durable. The last, however, has so many objectionable qualities, that
the number of eligible whites, may almost be said to be two--lead and
zinc. Of these, the former is blackened by foul air, and in oil, the
latter is wanting in body. In fact, there is but one white pigment which
approaches perfection--Chinese white; and this is only a water-colour.
TTITLE ON THE PRIMARY YELLOW
Yellow is the first of the primary or simple colours, nearest in
relation to, and partaking most of the nature of, the neutral white; it
is accordingly a most advancing colour, of great power in reflecting