GILDING 
gilding upon metals, the gold is brought 
into immediate contact with the other 
metal and they both remain firmly united 
merely by the attraction of adhesion 
subsisting between them. The simplest 
of all the kinds of gilding on metal, and 
which strikingly demonstrate the power of 
the affinity of adhesion, is one which is 
sometimes practised on plane surfaces of 
copper and iron, with considerable success. 
The metal being previously polished is 
heated to about the temperature of melted 
lead, and covered with a double layer of 
gold leaf : by the cautious application of a 
blood stone burnisher applied gently at 
first, and increasing the force of the pres- 
sure by degrees, the surface of the gold and 
copper are brought to touch each other in 
almost every point, and then adhere with a 
force proportionate to the completeness 
of the contact. The first layer being thus 
burnished down, a second is made to adhere 
in the same manner, and sometimes a third, 
if the gilding is intended to be very solid. 
The objection to this kind of gilding is its 
tediousness and the almost impossibility of 
using a sufficient pressure without injuring 
the evenness of the gilded surface : where 
these objections do not apply there cannot 
be a more effectual mode of gilding as is 
evident from the manufacture of gilt silver 
and copper wire. The bar, before it is 
committed to the wire- drawer, is plated 
with gold, by having several plates of gold 
successively burnished down upon it, and 
being then subjected to the stronger com- 
pression which takes place in wire-drawing, 
the gold and the other metal become so 
perfectly united as to form in a manner 
but one substance. 
The most usual method of covering the 
face of a metal with gold, is by means of an 
amalgam, or, as it is technically called, wa- 
ter- gilding. If the metal to be gilt is silver, 
the best method of proceeding is first to 
soak it in warm dilute muriatic acid, . that 
the surface may be rendered perfectly 
clean ; it must then be washed in clean wa- 
ter, changed two or three times, to get rid 
of the whole of the acid : being afterwards 
dried, and made moderately warm, a little 
gold amalgam, also warm, is to be carefully 
and evenly spread upon the silver, to which 
it will immediately adhere : when this is 
completed, the piece is placed upon a con- 
venient support over a charcoal fire, and 
while the mercury is evaporating, if any 
specks or places appear, which have es- 
caped the amalgam, a small piece is to be 
laid on, and spread with a brush, to supply 
the deficiency, without removing the article 
from the fire. After a time, the whole of 
the mercury will be driven off, and the 
piece, after cooling, being accurately exam- 
ined, will be found to be entirely covered 
with a thin coating of pale dull gold. The 
small roughnesses, and loosely -adhering par- 
ticles, are now to be removed with a scratch- 
brush, Which is made of some extraordi- 
nary fine brass wire, bound together into a 
tuft; by it the surface is rendered per- 
fectly smooth and bright ; but it still re- 
mains of a pale yellowish colour : this de- 
fect is next removed by wanning the piece, 
and smearing it over with gilders’, wax, a 
composition of bees’ wax, red ochre, verdi- 
gris, and green vitriol or alum. The wax 
being burnt off over a charcoal fire, and 
the piece quenched in urine, the colour of 
the gilding will be found to be much 
heightened ; if it is not sufficiently so, the 
application of a succeeding one will com- 
plete the desired effect, after which the 
work may be burnished or not, according 
to the taste of the artist. Instead of the 
common gilders’-wax, a mixture of equal 
parts of nitre, sal-ammoniac, green vitriol, 
and verdigris, moistened with water, will 
answer the purpose. 
Copper, and the alloys formed by its com- 
bination with zinc, are gilded nearly in the 
same manner as silver; but, as their affi- 
nity for mercury is considerably less than that 
of silver, it would be difficult to make the 
amalgam of gold adhere to the burnished sur- 
face of these metals by the same means, and 
with the same evenness, as takes place in the 
last case described. To obviate this incon- 
venience, advantage is very ingeniously 
taken of the action of nitric acid to facili- 
tate the adhesion of the copper and mer- 
cury, in the following manner. A piece of 
copper, a button fop example, if cleaned, 
by steeping it in acid, and subsequent wash- 
ing, and is then burnished either in a lathe, 
or by any other means : after this it is dip- 
ped in a neutralized solution of nitrate of 
mercury, and in the space of a few minutes, 
owing to the strong affinity of nitric acid 
for copper, the mercurial salt is decom- 
posed, the copper takes the place of the 
mercury, and at the same time the mercury 
is deposited in the metallic state on the sur- 
face of the copper, covering it entirely, and 
strongly adhering to it; the gold amalgam 
is now applied, and the rest of the process 
goes on as already described. By this me- 
thod of proceeding, a given quantity of gold 
