The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates (Birmingham, [ca. 1785])

THE ARTIST's ASSISTANT. 6t

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** lime, to the archal, previoufiy bruifed bv grinding.
<: This mixture muft be fuffcred to fhand till it ac-
*' quire a very blue colour. After which the fluid
*• muft be fuffered to evaporate, and the rcmain-
*' ing mafs, when it is of the confidence of a pafte,
t; muft be laid on boards to drv in fquare lumps."

If it is ufed in miniature paintings, care muft be
taken of the approach of acid, for that changes it in-
ftantly from blue to red ; though it will ftand if no
fuch accident intervene.

Class III.* Of YELLOW COLOURS.

King's yellow, when prepared well (which muft
be done by mixing fuiphur and arfenic by fublima-
tion) is an extremely bright colour, and a true yel-
low; but when mixed with white lead, and fevcral
other pigments, its colour flies or changes : this de-
fee!, joined to its naufeous fmell, and the notion of
its being a ftrong poifon, renders it unpleafmg, and
caufes it to be rejefted by many. Neverlhelefs, it
may be ufed on many occafions, with great advan-
tage, not only as a yellow, but by mixing it with
blue pigments, and forming a green. King's yellow
is prepared as follows:

* Class III.
King's yellow.
Naples yellow.
Yellow oker.
Dutch pink.
Englifn pink.
Light pink.
Gamboge.
Ma&icot.

I

Y E L L O W.

Common orpiment.
Gall ftones.

Terra di Sienna unbur'nt.
Turpeth mjneral.
Yellow berry wafh.
Turmeric wafh..
Zedoary wafh.
Tinfture of faffron.

" Take