174. MOSAIC GOLD

Mosaic gold, or aurum mosaicum, is used for inferior articles. It
is prepared in the following manner: 1 lb. of tin is melted in a
crucible, and 1/2 lb. of purified quicksilver added to it; when this
mixture is cold, it is reduced to powder, and ground with 1/2 lb.
of sal-ammoniac, and 7 ozs. of flower of sulphur, till the whole
is thoroughly mixed; they are then calcined in a mattrass, and the
sublimation of the other ingredients leaves the tin converted into
the aurum mosaicum, which is found at the bottom of the glass, like
a mass of bright flakey gold powder. Should any black or discoloured
particles appear, they must be removed. The sal-ammoniac used
here must be very white and clear, and the mercury quite pure and
unadulterated. When a shade of deeper red is required, it can easily
be obtained by grinding a very small quantity of red lead along with
the above materials.


175. DUTCH OR GERMAN GOLD

A gilding powder is sometimes made from Dutch gold, which is sold in
books at a very low price. This is treated in the same way as the
real gold leaf in making the true gold powder. It is necessary, when
this inferior powder is used, to cover the gilding with a coat of
clear varnish, otherwise it soon loses its metallic appearance. The
same remark applies, though to a less degree, to Mosaic gilding.


176. COPPER POWDER