886 'CASH 
in medals, it is very fimple and eafy ; as likewife where 
there are fuch as form only a right or any greater angle 
with the principal furface of the body ; but where parts 
jirojed in leffer angles, or form a curve inclined towards 
the principal furface of the body, the work is more difficult. 
The firft Hep to be taken is the forming the mould. In 
order to this, il the original be a baii-relief, or any other 
piece of a flat form, having its furface firft well oiled, it 
mufi be placed on a table, and furrounded by a frame, the 
Tides of which mud be at fuch a diftance from it as will 
allow a proper thicknefs for the fides of the mould. As 
much plafter as will be fufficient to cover and rife to fuch 
a thicknefs as may giye fufficient ftrength to the mould, as 
aifo to fill the hollow betwixt the frame and the model, 
mud be moidened with water, till it be juft of fuch confid¬ 
ence as will allow it to be poured upon the model. This 
mu ft be done as foot) as poffible ; or otherwife the plafter 
will concrete or fet, fo as to become unfit to be ufed. The 
whole mud then be fuffered to remain in this condition, till 
the plafter has attained its hardnefs ; and then, the frame 
being taken away, the preparatory caft or mould, thus 
formed, may be taken off from the fubjeft entire, and af¬ 
terwards left to dry. But, where the model or original 
lubjedt is of a round or ereft form, a different method 
muft be purfued j for the mould mud be formed in feveral 
pieces : or, if the fubjeft conlifts of detached and project¬ 
ing parts, it is frequently mod; expedient to cad fuch parts 
feparately, and afterwards join them together. Where 
the fubjedt forms a round, or fpheroid, or any part of 
fitch round or fpheroid, more than one half the plader 
muft be ufed without any frame to keep it round the mo¬ 
del ; and muft be tempered with water to fuch a confid¬ 
ence, that it may be wrought with the hand like very foft 
pafte ; but, though it need not be fo fluid.as when prepared 
for flat figured models, it muft yet be asmoift as is compa¬ 
tible with its cohering fufficiently together; and,, being 
thus prepared, it muft be put upon the model, and com- 
prcfled with the hand, or any flat inftrument, that the 
parts of it may adapt themfelves, in the mod pet-fed man¬ 
ner, to thole of the fubjed, as well as be compact with re- 
Iped to themfelves. When the model is fo covered to a 
convenient thicknefs, the whole muft be left at reft till the 
plafter be fet and firm, fo as to bear dividing without fail¬ 
ing to pieces, or being liable to be put cut of its form by 
flight violence ; and it muft then be divided into pieces, 
in order to its being taken off the model, by cutting it with 
a knife with a very thin blade ; and, being divided, muft 
be eautioufly taken off’, and kept till dry : but it muft al¬ 
ways be obferved, before tiie feparation of the parts be 
made, to notch them acrofs the joints or lines of the di- 
vifion, at proper diftances, that they rnay with eafe and 
certainty be properly conjoined again; which would be 
much more precarious and troubiefome without fuch di¬ 
rective marks. The art of properly dividing, the moulds, 
in order to make them feparate'from the model, requires 
more dexterity and fkill than any other thing, and does 
'not admit of rules for the moll advantageous conduct of it 
jn every cafe. Where the fubjeCt is of a round or lplie- 
roidal form, it is belt to divide the mould into three parts, 
which will then eafily come off from the model ; and the 
fame will hold good of a cylinder or any regularly curved 
.figure. The mould'being thus formed, and dry, and the 
parts put together, it muft be firft oiled, and placed in 
inch a pofition that the hollow may lie upwards, and then 
filled with plafter mixed with water, in the fame propor- 
Jionandmanner as was direCtedfor calling the mould : and, 
when the caft is perfectly fet and dry, it muft be taken 
out of the mould, and repaired where neceftary ; which 
finilhes the operation. 
Where the model forms curves which interfeCt each 
other, the conduCt of the operation muft be varied with 
jefpett to the manner of taking.the caft. But in faCt it 
muft be left to the good fenfe of the operator to judge, 
from the original fubjeCls, what parts will come off to¬ 
gether, and what require to be feparated. The principle 
‘ I N G. 
of the whole confifts only in this; that where under-work¬ 
ings, as they are called, occur, that is, wherever a ftraight 
line drawn from the balls or infertion of any projection 
would be cut or crofted by any part of fuch projection, 
fuch part cannot be taken off without a divifion ; which 
muft be made either in the place where die projection 
would crofs the ftraight line ; or, as that is frequently 
difficult, the whole projection muft be feparated from the 
main body, and divided alfo lengthwile into two parts : 
and where there ate no projections from the principal fur- 
faces, but the body is fo formed as to render the furface a 
compofttion of fuch curves, that a ftraight line being 
drawn parallel to the furface of one part would be cut by 
the outline, in one or more places, of another part, a di¬ 
vifion of the whole Ihould be made, fo as to reduce the- 
parts of it into regular curves, which muft then be treated 
as fuch. A good general rule is, to apply the plafter only - 
to fo much of the furface of the 'model as the eye can dil- 
tinClly lee. In larger maffes, where there would other- 
wife be a great thicknefs of the plafter, a corps or body 
may be put within the mould, in order to produce a hollow 
in the caft ; which laves plafter, and renders the caff- 
lighter. This corps may be of wood, where the forming 
a hollow of a ffraight figure, or a conical one with the bafts 
outward, will anfwer the end : but if the cavity require 
to be round, or of any curved figure, the corps cannot be 
drawn while entire ; and confequently Ihould be of fuch 
matter as may be taken out piece-meal. In this cafe, the- 
corps is bed: formed of clay, which mud be worked upon 
wires to give it tenacity, and fnlpended in the hollow of the 
mould, by crofs wires lying over the mouth; and, when 
the plader is fufficiently fet to bear handling, the clay mulf 
be picked out by a proper inftrument. ‘Where it is de- 
fired to render the plafter harder, the water with which it 
is tempered ftiould be mixed with glue fize, which will 
make it very firm and tenacious. 
In the fame manner, figures, buds, &c. may be caft of- 
lead, or any other metal, in the moulds of plafter ; though 
the expence of plafter, and the. tedioufnefs of its becoming 
fufficiently dry, when in a very large mafs, to bear the 
heat of melted metal, render the life of day preferable: 
where large fubjeds arc wanted. The clay, in this cafe, 
ftiould be waffled till it be perfectly free from gravel or 
itones ; and then mixed with a third or more of fine fand 
to prevent its cracking; or, inftead of land, coal-aihes 
lifted fine may be ufed. Whether plafter or clay be em¬ 
ployed for the calling in metal, ic is extremely neceffury to 
have the mould perfectly dry ; otherwife the moifture, be¬ 
ing rarefied, will make an explolion that will blow the 
metal out of the mould, and endanger the operator. 
Caftsof medals, or fuch fmall pieces as are of a limilar 
form, may be made in plsfter by the method direded for- 
bas-relievos. Indeed there is nothing more required than 
to form a mould by laying them on a proper board ; and 
having furrounded them by a rim made of a piece of a 
card, or any other pafteboard, to fill the rim with foft 
tempered plafter of Paris ; which mould, when dry, .will 
fervefor feveral calls. It is neverthelefs a better method, 
to form the mould of melted fulphur; which will produce 
a ftiarper impreffion, and he more durable than thole made 
of plafter. Threads are like wile frequently madeof ful- 
pflur, which being melted mull be treated exndly in the 
fame manner as plafter. For taking calls from medals, a 
mixture of brimftone and red lead are very proper : equal 
parts of thefe are to be put over the fire in a ladle, till 
they fo.ften to the confidence of pap ; then they are kindled 
with a piece of paper, and ftirred for fome time. The 
veil'd being afterwards covered dole, and continued on. 
the fire, the mixture grows fluid in a few minutes. It is 
then to be poured on the metal, previoufty oiled and wiped 
clean. Thefe calls are very neat; their colour, fome times 
a deep black, fometimes a d-ark grey : they are very du¬ 
rable ; and, when foiled, may be walked clean in fpirits 
of wine. Some recommend tin-foil for taking oft' cads 
from medals. The thinned kind of this Ihould be laid 
i over 
