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]

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1 cm

and indeed, it is the moft ufeful, and moft ufed of
any fubftance whatever for that purpofe. It is pre-
pared only by levigation; to which its texture, not-
withstanding its being a femi-metal, very well fuits.

Glafs of antimony is alfo ufed fometimes, in enamel
painting; being itfelf a fine tranfparent orange
colour. But as it wants body, it has no great effect
but in compofitions.

Orpiment has been alfo ufed in enamel for pro-
ducing a yellow colour; but it is very tender with
regard to the fire, and requires fo foft a flux, while,
at the fame time, antimony, properly managed, will
fo well fupply the place of it, that it is rarely ufed.

Powdered bricks have been alfo ufed for com-
pounding yellow colours in enamel; but as they act.
only in confequence of the oker they contain, they
are certainly inferior to the prepared okers we have

The moft active flux amongft falts is borax ; which
indeed, poffeffes this power in the greateft degree hi-
therto known of any Ample whatever. The next is
lead; which vitrifies with a very moderate degree
of heat, and affimilates to glafs with itfelf, not only
many kinds of earth, but all metals and femi-metals;
except gold and filver in their entire ftate. Arfenic
is the next powerful flux, only it requires to be
fixed, by conjoining it with fome other body al-
ready vitrified; otherwife it fublimes and flies away
before it arrives at the vitrifaclive heat. The feve-
ral kinds of falts have the next degree of fluxing
power; and among them fea fait poffeffes the great-
eft. But they are not fufhciently ftrong themfelves
to form an enamel flux foft enough to be ufed in
painting. Though, as they are colourlefs, which
U is
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