For a gold varnish for bronze objects refer to BRASS.
_Obs._ Several analyses have been made of ancient cutting instruments,
from which it appears that the proportion of tin varies from 4% to 15%; a
fact which tends to prove that more depends upon the exact mode of
tempering the alloy than on the relative proportions of the ingredients.
Lead and zinc are inadmissible in bronze for this purpose. One or two per
cent. of iron may, nevertheless, be added with advantage. The ancient
bronze used for springs contained only 3% to 4% of tin. The edges and lips
of bronze mortars must be carefully tempered by heating them to a cherry
red, and then plunging them into cold water, as unless so treated they are
very apt to be broken in use. See BELL-METAL, BRASS, GUN-METAL, &c.
=Bronze'-powder.= _Syn._ BRONZE. A name given to various powders having a
rich metallic appearance, which they retain when applied on varnish, or
when mixed with it, as in surface bronzing.
_Prep._ 1. GOLD-COLOURED:--_a._ From Dutch-foil, reduced to an impalpable
power by grinding. Cheap and looks well, and is very durable when
varnished.
_b._ From gold-leaf, as the last.
_c._ Precipitated powder of gold.
_d._ From verdigris, 8 oz.; tutty powder, 4 oz.; borax and nitre, of each
2 oz.; bichloride of mercury, 1/4 oz.; grind them together, make the
mixture into a paste with oil, and then fuse it; when cold, roll it into
thin sheets or leaves, and grind it as in No. 1.