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. 219

and a very little arfenic or tartar; -when thefe are put
into fufion let them incorporate.

Some take of copper three parts, of pewter one
part, and a little filver, antimony, and white flint.

Others do it with one part of lead, and two parts
of filver.

After the metal is formed and caff, it is requifite
to have it fmooth and well polifhed ; the firft is done
with emery, then with powder of brimftone or tin
afhes, or elfe with tripoli; thepolifhing is done with
pulverifed chimney foot of wood fires, and the afhes
of willow or cedar, which will give it a fine luftre.
The emery is ground to a fine duft, and moiftened
with water; or, fteel mixtures are alfo made out of
one pound of pewter, and one third of copper ; when
thefe are melted, add two ounces of tartar, and one
ounce of orpiment, and when evaporated, pour the
mixture out into the mould. The calling of a flat
mirror, or looking glafs, is done upon a flat board,
which muft be made dry and warm, and covered with
rofin or pitch ; by this means the mirror is fixed to
the board ; when cold, rub it with fand and water,
then with emery, or flower of brimftone, and at laft
polifh it with tin afhes.

Another fort of fteel mixture for mirrors :— Take
good new copper, of that fort which is ufed for cop-
per wire, eight parts; fine Englifh pewter one part;
bitmuth five parts; put it together into a crucible and
melt it. Then greafe the mould all over with tallow,
in order to caft your metal into it ; when it is in
fufion, dip a hot iron into it; what flicks to it let
cool. If the colour is inclining to white it is nVht;
but if to red, you mutt add fome more pewter, until
has ifs right colour. Obfcrve that whatever

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