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. 147

them fuch others, with refpect to their effecl on fe-
veral of the fubftances that compofe the colours, as
renders the methods of ufing them difficult and
complex.

Of the fubftances ufed for forming the body of enamel^

or fluxes.

White fand is ufed as a body for the fluxes and
grounds of enamel : it fhould be reduced previoufly
to an impalpable powder, in order that it may be
mixed more intimately with the other ingredients ;
which not only accelerates the vitrification, but
renders the glafs much more perfe£l. The kind of
land proper for this purpofe, is that brought from
Lynn, in Norfolk, and called by the name of that
place.

Flints are ufed for the fame purpofe as the white
fand ; and it is proper to ufe them, when that can-
not be procured of the right kind. They require to
be calcined before they are applied to any purpofe
of vitrification. This is to be done, by putting them
into any fire, and continuing them there till the
whole fubftance become white ; when they muft
be taken out ; and, while in their full heat, im-
inerfed in cold water, and kept there for fome time.
By fuch treatment, they will be rendered of a very
brittle and calcarious texture, and very eafy to be
powdered ; which muft be done to a perfect degree,
for the reafon above given. Where fmall quantities
of the matter of any kind of enamel is to be pre-
pared, calcined flints are preferable to fand; as they
are much more eafily reduced to an impalpable pow-
der, and the trouble of the previous calcination is
very little.

T 2 There