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])

ai8 THE ARTIST'S ASSISTANT.

per, and then add the pewter to it; when both are
in fufion, pour it out, and, when cold, beat it to pow-
der; then take twelve ounces of red tartar, a little
calcined tartar, three ounces of faltpetre, one ounce
and a/half of alum, and four ounces of arfenic ;
mix and ftir this together, and, after it has done
evaporating, pour out the metal into your mould ;
let it cool, and, when polifhed, you will have a fine
mirror.

This is the compohtion which is commonly called
the fteel mixture.

Some artiftswill have the arfenic omitted, becaufe
it is apt to turn the mirror into a deadifh blue co-
lour, and requires new polifhing every time one
wants to ufe it, and they think that copper and pewter
are fufficient to anfwer that purpofe.

Another :—Take an earthen pan that is not glazed,
and has flood the fire ; put into it two pounds of tar-
tar, alfo the fame weight of cryftalline arfenic, and
melt it on a coal fire. When this mixture begins to
fmoak, add to it fifty pounds of old copper, and put
it into fufion for fix or feven hours, fo that it may be
•well cleanfed ; then add to it fifty pounds of pewter,
and let them melt together ;. after this, take up fome
of the mixture with an iron, to fee whether it is too
hard and brittle ; iffo, then add a little more tin ; and
when you have the right temper, fling four ounces
of borax over it, and let it ftand in the furnace un-
til it is diffolved, then pour it into your mould and
let it cool ; when it is cold, rub it firft with brim-
flone and then with emery; and after the furface is
made fmooth and even, polifh it with tripoli or tin
afhes, and give it the finifhing ftroke with lamp-
black; or, take copper one part, pewter three parts,