» ~The first circumstance to be attended to in wash- 
. gilding, is to make the surface of the metal perfectly 
free from all scurf, ‘tarnish, or oxidation; for the co- 
vering of gold upon the metal unites therewith by a 
_ kindof, an ion, and forms a superficial alloy, 
Lag would * Fr doar the smallest coat of tar- 
nish, wre Ve fetter 1 + 
. The cleaning is performed,by pickling the metal, in 
a solution of aqi sata water: the strength of the 
solution is immaterial, except with respect. to the time, 
that the, metal-must,remain in it., A quantity of acid, 
_equal to-one-fourth of the water, will clean the metal; 
‘in afew minutes; but if weaker, is equally eflective in. 
_ a longer time: and if the article is accidentally left in 
the pickle for a long time, it will not be injured, For 
; eee coarse articles, a strong solution of sal nixon, 
— op.sal.ammoniac, is employed ; and to. render it more, 
active, the metal is. heated and plunged ‘into it : this, 
} raises a black or brown oxide over the whole surface, It 
Acid, is then dipped in the pickle of aquafortis, which throws 
off a slight: scale from the surface, and renders the me- 
tal clean at once; and it is put into clean water, to pre- 
vent the farther: action: of the acid from producing a 
emeleboter ee eee is performed, » | brie 
| For the,best work, the aquafortis pickle is used cold,, 
and the cleaning is, performed) by ‘the friction of a 
seratch-brush, formed, of» fine brass wire instead of 
hairs. The brush is sometimes made of a circular form, 
and. mounted, on a spindle, turned rapidly by the mo- 
re 
4 
” lathe, whilst the work ‘is presented to the brush. But 
far delicate work, such as the wheels and other parts of 
watches, a very delicate hand brush: is used.; and here, 
_ it must be noted, that when the: steel! arbors of the 
wheels, or any other part of steel, are attached to the’ 
work, it must not be dipped )into the:pickle, but. the, 
pickle should be made stronger, and only the scratch-, 
___ brush dipped:into it, before the work is brushed with, 
. it. The steel must be frequently dipped into clear, 
“» © water during the brushing, to prevent the action of any 
ha Oe cites eolene : ms oo 
ning To amal perfectly upon the surface of 
the article which is te mateo acid, called the quick- 
ening, is used. This is made of aquafortis, (nitrous acid), 
with a small Lrtgm g of mercury dissolved in it, so.as, 
| to give it a milky whiteness, ‘Tlie article being dipped 
] =. into this, attracts a.coat of the solution of mercury, over 
the whole surface, in an instant; and with this|prepa- 
__ ¥ation; the amalgam is applied with the pencil.. ‘This is 
. a piece of flattened copper wire, fixed in a handle; it is 
occasionally dipped into the quickening, then touching 
Mication the amalgam with it, it will take up’a small quantity; 
se smal. which is rubbed upon the work, and spreads or ‘flows 
in an instant over all the which have been touch- 
ed by the qitickening. The action of the quickening 
regard from the greater affinity. ef] the nitrous 
copper 
_ which, the acid takes to the copper the instant it is ap- 
plied upon it, and» leaves the mercury: precipitated 
upon the surface, This’ coating of m facilitates 
the spreading of the amalgam when jit is applied, al- 
though it may be spread without it, by merely dipping 
aquafortis; then: into the am: i 
the surface’ of the 
for deli¢ate works; 
tsof steel, Ano- 
iia cupor jar, mercury and = Tocnareat ip 
eee CUES es oe : : + . a 
sistency of thin cream. “Into thivthe articles are dip 
et wk. 
aos 
GILDING 
tion of a foot-wheel and treddle,,in ‘the manner of a. ’ 
than for the mercury ; in'conseqyuence'of th 
277 
ped, and become at once : pester! --coated with the Gilding. 
amalgam. We have seen, this method used by a but- “—v—~ 
ton manufacturer, and it succeeded very well, with 
scarcely ‘any trouble; but, it is only, applicable on a 
large scale, for this amalgam will not keep long, because 
the acid turns the mercury black, by an oxide which 
will not pass off iu the.drying. They can only mix up, 
in this way, as much amalgam as they intend to use in, 
a very.short time. Without acid, the amalgam will 
keep any length of time. 
. The next step in the operation is the drying off, or eva- Drying off 
porating the mercury, For this a small charcoal stove or, stove. 
oven is used ; itismerely a square opening, surrounded, 
by brick on every side, except the front, and a flue pro- 
ceeds from the top. It is made of a size proportioned 
to that of the work intended to be dried in it. As it 
is not intended that the draught of. air shall be rapid, 
the stove may be placed in the lower part ofa chimney, 
which is open all round the stove; so as to admit part 
of the current of air to ascend into. the chimney with- 
out passing through the fire; and the char being 
laid upon a small stone hearth, without any grate, it 
does not burn away very rapidly. The front.of the 
chimney. should be closed by a window-sash, which 
draws-up and down, leaving just room enough beneath 
for the gilder to-put his arms and hands into,the chim- 
ney, while he sees his work in the stove through the 
glass, which prevents his inhaling the pernicious vapour 
of the mercury. A drawing of an apparatus of this 
kind is represented in Fig. 9. of Plate CVII. Burton, 
Manvracrore, with an additional apparatus to con-, 
dense and preserve the mercury dissipated by the eya- 
poration. The gilder, is generally seated before this 
stove, and holds the work in a pair of iron. pincers, 
over the burning charcoal, till he sees it change colour 
from the white silyery appearance produced. by the, 
amalgam, to a gold colour, which gradually comes on 
as the mercury passes off. 
Atithe first application of the heat, before it is suf-, Operation of 
ficient to. make the mercury evaporate, the amalgam drying off. 
will-be'seen to grow. more fluid, and flow as it were 
upon the surface. In this: state it is lable to collect 
more to one part of the work than others, probably be- 
cduse the heat is not equal in all parts, but renders the 
amalgam more fluid in some places than in others, 
To counteract the.effect of this tendency, a brush of Spreading 
soft hog’s haiv.is frequently drawn oyer the work, to the gold 
spread the amalgam perfectly equal over the whole sur- by * brush. 
face. This is a part of the process. which requires 
much attention from the workman ; for if he, does not 
spread it well, the parts where the mercury accumu- 
lates will form whitish. spots when dry; and_ these 
spots will afterwards tarnish, and at length turn black, 
haying very little of the'gold Jaid upon them. A great 
deal depenie upon the heat being very equally and re- 
gularly applied, until the mercury begins to dry off, and 
amalgam becomes fixed. The common gilder’s 
stove. is: very ill calculated to attain this equality of 
heat; : If the work has any cavities or hollow parts, into 
which the is liable to be, accumulated by the 
brush, it must be dislodged by shaking the work, The 
hait of the brush must be very soft and. pointed, by 
rubbing it upon a piece of pumice-stone ; and where there 
is any: extent/of ‘surface to be gilt, the brush.must be 
drawn in one direction, because it leaves.a sort of grain, 
which) will’ haye.a disagreeable appearance if it is not 
laid straight...) . , 
It-is usual for the gilder to- have ay a aa ag 
e intends. to 
Gilding ° 
into which he puts a few of the pieces h 
pa, 
