276 
Gilding. gree as is done at present. ‘From the information of 
— ~~ Pliny we learn, that their thickest leaves were called 
braclee prenestine, because a statue of Fortune at Pras 
nestina was gilded therewith. An ounce» of gold 
formed 750 of these leaves, each being 4 fingers orS 
inches squaré: this is 9 square inches in each leaf, or 
47 square feet very nearly for the whole ‘ounce. ‘The 
Romans employed thinner Jeaves, which they called 
braclew questorie. From the great malleability of gold; 
the moderns have discovered: means by which it:can 
be reduced. to such extremely thin leaves, that, not- 
withstanding its high specific’ gravity, a given weight 
' of gold can be made to cover a greater surface than any 
Superficies other metal. » An experiment by Ms Reaumur:shewed 
ofa grain the superficies of a grain troy weight of gold'leafto be 
of gold leaf. 49 square inches and three-tenths, This is at’the rate 
of 141 square feet per ounce, and the thickness of'such 
a leaf has been estimated at the 7,);.;th part of an 
inch. \ Mr Boyle found that ‘a grain might’ be spread 
to 50 square inches and seven-tenths. This gives 169 
’ square feet for the ounce; and; by the: same mode of 
estimation, the thickness would. be only the:,.;4—,d 
part of an inch. Gold is-not at all liable; like other 
metals, to tarnish or oxidate by the action of the'air or 
damp ; and therefore this thin covering is very-dura- 
ble. It is not susceptibleof any other decay or waste, 
than from those causes which produce friction or abra- 
sion of the gilded surface. 
Gilding ‘is performed either upon metals, or upon 
wood, leather, parchment, or paper’; but three distinct 
methads are employed ; the first called wash or water 
gilding, in which the gold is spread whilst reduced to 
a fluid state by solution in mercury ; 2d, Leaf gilding; 
either burnished or in oil, is performed by cementing 
thin leaves of gold upon the work, either by size or by 
oil ; 3d, Japanners gilding, in which gold dust or pow= 
der is used instead of leaves. ; 
Wash or water gilding —The method of gilding by a 
solution of gold is only applied to metals. The goldis 
first dissolved: or reduced to the consistency ofa semis 
fluid, by amalgamation with mercury.’ In this state, 
by the assistance of an acid, it can’ bé spread or washed 
evenly upon-every part of the surface of the article to 
be’ gilded ; the mercury is afterwards evaporated by 
heat, and leaves a covering of pure gold, the thicke 
ness of which is inconceivably small, although forming 
Its applica- a most perfect surface. By this’ method, brass orna- 
tions. ments, watch-cases, buttons, and jewellery of’ all de- 
scriptions, are made to represent gold. The latter 
branch of the art is carried to such a high degree ‘of 
perfection, that the deception can only be detected by 
the weight of the article, by cutting into it, or by some 
chemical test. 
A mixture of copper and brass is the metal most 
commonly employed for this kind of gilding : pure cop- 
per does not ily receive the mercury ted 
with the gold; and, being of a soft and rather porous 
nature, requires more gold to» produce an equally bril- 
liant cover About one-seventh part of brass, be- 
ing mixed wiih the copper, renders it harder, and makes 
the gold spread very readily: brass itself will receive 
Proper me- @ Very fine surface of gilding. “The endeavour of the 
tals for workman is, to make such a mixture of brass and cop- 
wash gild- per as will produce nearly the same colour as the gild- 
NBs ing is intended to have ; for a great variety of shades 
in the colour of the gold can be produced by a subse- 
quent process, after it has been laid on ; but it requires 
less trouble to give the gilding the same colour as the 
metal which is beneath, than to make a different shade. 
Three kinds 
of gilding. 
By amal- 
gam. 
GILDING. 
, amoment,, till a 
‘ing ; for if the gold and mercury are pure, and the amal- 
In effect, thé gold adheres to the metal by forming a | 
very — amalgamation or alloy therewith ; hence 
the gold will partake of the colour of the metal. A se- 
cond coat of gilding laid on will:have a opera ceed 
ance of. pure gold, and will havea more d bril- 
liancy than an equal quantity of gold spread upon the 
metal at one process. et th 4a TRI i, 
Silver takes a fine ‘surface of gold, and of a yellow 
colour, unless it is gilt twice over, sand coloured afters 
wards: ' M fa heist ania seh A” “eerie 
' Tron and steel will not take the amalgam, asthe mers 
cury has no affinity for these metals,’ ~\ ©“) Ss ea” 
Tin, zinc, lead, or other of the! baser metals; are nes 
ver gilded by. amalgam: “they would deteriorate:the 
gold too:much, nor would they bear a sufficient heat; 
To amalgainate the gold for wash. gilding, ni 
quantity is put into a crucible, or an iron ladle, withabout o gold 
six times its weight of mercury. The ladle or crucible "7° 
should be rubbed on the inside with whitening, to pres 
vent any waste ; and beingput upon a charcoal fire, and 
gently heated, the mercury will soon dissolve the gold. 
To assist the solution, it should be stirred with an iron 
wire. The heat:should not be. sufficient to-evaporate 
the mercury, at least not until ee 
is nearly effected ; the heat may then be increased for 
is seen to rise from the cruci« 
ble. The amalgam being made, is thrown out into was 
ter, where a small. portion of mercury will be seen'to 
separate itself. This contains very little if any gélds 
but the real amalgam forms a small lump of paste, of 
nearly the same.consistence with butter ; but it will be. 
observed to have particles of mercury intermixed with 
it. To remove. these, the» amalgam “is twisted up in a 
piece of fine wash leather, and gently pressed with the 
finger and thumb: the mereury will: through the 
res of the leather; and leave the gam fit for use. 
= this state it is the colour of ‘silver; without/any ap- 
pearance of gold, ‘and does not contain more than 
twice the weight of mercury to'that of the gold. The = = 
mercury whi waldo fat ra-nteeetiges citer 
be reserved: for mi ‘future , asit will pro- * 
bably contain a small proportion of the gold. 
Some workmen vary this process by heating the gold 
to redness, and heating the mercury to the point of 
evaporation ; then, throwing the hot gold into the mer= 
cury, the amalgam is quickly ieffected. We do not 
know any difference of effect which should’ give the 
preference to either of these processes. © Lite, 
-» It-is essential that both the gold and the mercury } 
should be pure.» The mercury of ‘commerce is almost shov 
always-adulterated with lead, which is prejudicial 
to the gilding. ‘It should-be:s istilling the 
mercury in an ivon retort, with a gentle heat:~ this will 
leave the lead in the retort ; orthe mercury may be re~ 
vived from cinnabar in a:very purerstate. Nothing can 
be gained by employing gold of an inferior quality, as 
it will always require a greater proporti u 
the same covering, and the beillimey will be much im~ 
paired. ' net ED tb Tita geet eee 
It has been recommended to grind'the amalgam on: 
marble stone, or inva glass mortar, and to w: ‘it ‘con~ 
tinually with a solution of common salt in water. This 
8. 
& 
g, 
e 
z 
3 
= 
have never met with any artist who practises this 
gam is not , 80 as to oxidate the mereury, it 
will be unnecessary. . } 
