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pieces by string (as described at chapter VII) made over the whole.
This jacket keeps all together for the ultimate casting by the pegs in
its surface made by the holes of the pieces underneath.

The ultimate cast is made by plaster being poured into a hole left at
one end of the mould for that purpose. Should this ultimate casting be
wanted hollow, it will be necessary to shake the plaster, when poured
in, around the mould in the manner described for making wax fruit.

Small undercut articles may be cast from, by making a mould of best
glue--"gelatine glue"--which readily stretches enough to "clear"
undercuts and come off the model. To get a model from this glue mould,
cover the original model you wish to cast from with as thick a
covering of clay as you wish your gelatine mould to be when run; upon
this pour plaster to form a "jacket," letting its top and bottom rest
on the top and bottom of the original model. When the clay is removed,
and the "jacket" fitted on again, it will, of course, only touch at
top and bottom, leaving an interspace all over the remainder of the
model. A hole being now cut in the "jacket," the glue [Footnote: Made
by steeping for a night, and allowing it to absorb all the water it
will, throwing away the surplus, and boiling the remainder in the
usual manner in a glue-kettle. Pour on when hot, not boiling.] is
poured in over the original oiled model, and fills up the interspace
left by the removal of the clay. When cold, it, of course, forms a
mould into which plaster can be run, in the usual manner, to form the
ultimate model.

Piece-casting of large subjects, where the various parts are cast and
then fitted together afterwards, is best understood by learning a
little from some Italian modeller, or looking over the seams
(representing the "piece-casting" joints) in some one or other of
Brucciani's reproductions, which may be seen in almost any art gallery
or museum.

One great advantage of this system is, that by its means large models,
if built up in ordinary field clay, or by any other means, may be cast
from in plaster or in metal by the intervention of piece moulds,
failing which it would be impossible to do so. The resultant model, if
in plaster, is not cast solid, but is hollowed out in the casting--to
prevent weight--by "cores" being inserted in the moulds. "Casting
sand" is, however, necessary when casting in metal, together with all
sorts of technical appliances and knowledg