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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THE ARTIST'S ASSISTANT. 153

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
given.

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
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