Called Also Mineral Yellow Is Found In Most Countries And Abundantly
:
ON THE PRIMARY, YELLOW.
in our own. It differs much both in constitution and colour, ranging
from a tolerably bright though not vivid yellow to a brown-yellow, and
is generally of a warm cast. Its natural variety is much increased by
artificial dressing and compounding. The best yellow ochres possess no
great force, but as far as they go are valuable pigments, particularly
in fresco and distemper, being neither subject to change by ordinary
l
ght, nor sensibly affected by impure air, or the action of lime. By
time, however, and the direct rays of the sun, they are somewhat
darkened. Like other ochres, they may be safely used in admixture with
pigments which are themselves permanent. With carmine and the cochineal
lakes, or intense blue, the ochres are best not employed.
The impunity with which yellow ochre bears foul gas is one of its many
recommendations. No immediate effect whatever is produced by
sulphuretted hydrogen, and only a slight dirty brown tint is imparted
by its prolonged action. This discolouration a short exposure to air and
light quickly removes. By keeping the ochre sufficiently long in contact
with sulphide of ammonium a jet black is obtainable, but a rub of it in
a moist unwashed state completely regains its yellow hue in a day or so.
Hence, yellow ochre compounded with pigments which suffer from an impure
atmosphere doubtless acts as a preservative agent.
Yellow ochre is usually employed in the distance and middle ground of a
landscape. It possesses a slight degree of turbidness, and is esteemed
for this property, which is considered to give it a retiring quality. By
admixture with Antwerp blue or indigo it affords a fine range of quiet
greens, also a very serviceable yellowish drab with Vandyke brown. The
ochre is valuable in warm skies, the sails of ships and boats, sandstone
rocks and cliffs, buildings, hay, sheep, &c. It does not compound kindly
with any of the cold colours, and should therefore be used as a wash
over others that are dry, when required to qualify their tints.
TTITLE ROMAN OCHRE
Is rather deeper and more powerful than the preceding, as well as more
transparent and cool in tint. In other respects it is similar, and forms
with Antwerp blue and indigo a like excellent range of greens. We may
observe, however, that as indigo is not a permanent pigment, the colours
it yields by admixture cannot be durable as far as the blue is
concerned. Roman ochre and brown madder are admirably adapted for red
sails, and autumnal effects of foliage.
TTITLE BROWN OCHRE,