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])

224 THE ARTIST'S ASSISTANT.

<: Take of tin one pound, of flowers of fulphur fe-
t: ven ounces, and ot fal ammoniacus and purified
t: quick-fdver, each half a pound. Melt the tin and
<c add the quickfilver to it in that ftate ;. and when
i: the mixture is become cold, powder it, and grind
'■' it with the fal ammoniacus and fulphur, till the
<: whole be thoroughly commixt. Calcine them then
t; in a mattrafs. and the other ingredients fubliming,
'•' the tin will be converted into the aurum mofaicum ;
" and will be found in the bottom of the plafs like
': a mafs of bright flaky gold powder; but if any
" black or dilcoloured parts appear in it, they mull
*' be carefully picked or cur out."

Where the appearance of brafs is defigned, the
gold powders, or the aurum mofaicum, may be
mixed with a little of the powder called argentum
mufivum ; the preparation of which is treated of
under the article filverincr.

Where the appearance of filver is wanted, the
argentum mufivum is the belt and cheapeft method ;
particularly as it will hold its colour much longer
than the true hlver ufed either in leaf or powder.

Where no cement is ufed in bronzing, the pow-
der muft be rubbed on the fubjecb intended to be
bronzed, by means of a piece of foft leather, or
fine linen rag, till the whole furface be coloured.

The former method of ufing cement in bronzing
was; to mix the powders with ftrong gum water, or
ifmglafs fize ; and then, with a brufh, or pencil, to
to lay them on the iubjeel". But at prefent fome ufe
the japanners gold fize ; and proceed in all refpefts
in the fame manner as in gilding, with the powders
in other cafes; for which ample directions will be
given.

This