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. 223

cluced by grinding a very fmall quantity of red lead,
with thefe powders; or the proper powder of cop-
per may be ufed ; and may be prepared as follows :

" Take filings of copper, or flips of copper-plates ;
" which diffolve in any kind of aquafortis, and put
<: into a glafs receiver, or other proper formed veflel.
<; When the aquafortis is faturated with the copper,
" take out the flips of the plates ; or. if filings were
<: ufed, pour off the folution from what remains un-
" diffolved ; and put into it fmall bars of iron, which.
" will precipitate the copper from the aquafortis in
" a powder of the proper appearance and colour of
<; copper. Pour off the water then from the powder,
4: and wafh it clean from the falts, by feveral fuc-
{; ceffive quantities of frefh water."

The true gold powder may be well and eafily
made by the following method :

" Take any quantity of leaf gold; and grind it

with virgin honey, on a ftone, till the texture of
<: the leaves be perfectly broken, and their parts di-
" vided to the minuteffc degree. Then take the mix-
li ture of gold and honey from off the ffone, and put
t: it into a china or other fuch bafon, with watery
'•' then flir it well about, that the honey may be melt-
u. ed, and the gold by that means freed from it. Let
" the bafon afterwards fland at reft, till the gold be
" fubfided; and when it is fo, pour off the water
" from it, adding frefh quantitiestill the honey be en~
<; tirely warned away ; after which, the gold may be
44 put on paper, and dried for ufe."

The aurum mofaicum, which is tin coloured, and
rendered of a flaky or pulverine texture, by a chemi-
cal procefs, fo as greatly to refemble gold powder, is
prepared in the following manner:

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