HOW TO MAKE PLASTER CASTS.
IT is not at all difficult; anyone can succeed in it who will take the
pains to follow carefully the directions given here for making plaster
casts. Without the knowledge of drawing or modelling you can in this
way reproduce almost any article in a very short time.
Casting in plaster is really so simple a process that even a child can
soon learn to manage it nicely.
You will need a board, about a foot and a half square, upon
which to work, fifteen or twenty pounds of clay, five pounds of
plaster-of-Paris, a cup of warm melted lard, and several small wooden
pegs; these can be made of wooden tooth-picks or matches broken in two.
Select an object with few angles and a smooth surface to experiment on;
a firm round apple will do. Rub the lard all over the apple until every
particle is greased; then lay it in the centre of your board. Take some
clay and pack it around it just as high as the middle of the apple,
forming a square, as in Fig. 168. Smooth the clay off on the edges and
stick pegs in diagonal opposite corners (Fig. 168); then with more clay
build a wall close around the apple and its case, making the sides
one inch higher than the top of the apple (Fig. 169). Put a cupful of
clear water into a pan or dish, and stir in enough plaster of Paris to
make it like batter; pour the plaster over the apple, filling the clay
box to the top. This makes a half mould of clay and a half mould of
plaster.
[Illustration]
When the plaster is hard, which will be in a very short time, pull away
your clay wall, and take out the apple and half plaster mould together,
lifting the apple from its half clay mould.
Remove the clay from your board and set the plaster mould containing
the apple in the centre. Rub lard over the apple and upper edge of the
mould, build around it the clay wall, as you did the first time; roll a
small piece of clay into a slender conical shape and stand it upright
on top of the apple, as in Fig. 169. This will make a hole through
which to pour the plaster when filling the completed mould, and it must
stand high enough to reach above the top of the clay wall.
Pour the plaster over the apple as at first, and let it set or harden.
Take away the wall of clay once more, and carefully separate the two
parts of the mould with the blade of a table-knife; remove the apple,
and all is ready for the final cast which is to produce your plaster
fruit (Fig. 170).
Thoroughly grease the inside of your mould, fit the two parts together,
and wrap and tie them with string to hold them in place.
Pour in the plaster, through the hole left in one-half of the mould,
until it is quite full; then gently shake it to send the plaster into
all small crevices.
Let your mould stand without moving again until sufficient time has
elapsed for the plaster to harden; then gently separate the two parts
and you will find a perfect cast of the apple.
The ridge made by the joining of the mould you must scrape off with a
sharp knife, or rub with sand-paper.
In taking casts of almost any object not too complicated, this same
method must be employed. The only difficulty lies in deciding just
where to place the dividing-line, which must be exactly at the broadest
part of your model, otherwise you will break your mould in taking the
object out.
In casting a hand the clay must be built up around each finger to
precisely its widest part; therefore it is a good plan, before
commencing, to mark on the hand, with a fine paint-brush and ink, the
line that is to be observed.
When making casts of long objects, or those that are larger at one end
than the other, such as vases, always lay them on one side, as a much
better mould can be obtained in that way.
I have read that if milk-and-water is used for mixing the plaster, or,
after the cast has hardened, if a little oil, in which wax has been
dissolved, be applied to the surface, it will take a high polish; and
if left for a while in a smoky room it will acquire the look of old
ivory.
The same writer also states, without giving the proportions, that
liquid gum-arabic and sufficient alum in solution, mixed and put into
the slip or soft plaster, will make the cast so hard that it can be set
as a panel in a cabinet.
The dead white of plaster-casts is frequently objected to when they are
wanted for ornaments; but that difficulty is easily overcome by mixing
dry colors with the plaster before wetting it.
[Illustration]
A small quantity of yellow ochre will make the plaster creamy or
ivory-like; brown will give a wood color, and red a terra-cotta.
Plaster-casts can also be bronzed with gold, red, or green bronze,
which makes quite handsome ornaments of them. A plaster panel in
bass-relief, bronzed with gold bronze and mounted on black or
dark-colored velvet, is an exceedingly rich wall decoration.
To mount a panel of this kind you must first secure a smooth, flat
piece of board, not more than half an inch thick, and just large enough
to allow about four inches of the background to show all around the
panel when it is mounted. Cover the board with velvet or velveteen,
bringing it smoothly over the edges, and tacking it down at the back.
Fasten on it a small brass hook. Fig. 171 is the best kind to use,
which is tacked to the board with small, brass tacks.
Make a ring or loop for hanging the panel in this way:
Take a piece of wire about three inches long, form a small loop in the
middle, and give the wire several twists; then bend the ends out on
each side.
Scrape a narrow place in the top edge of the panel, just long enough
to admit the wire, and about half an inch deep; then place the wire in
this little ditch and fill up the hole to the top with soft plaster.
When this hardens the ring will be quite secure. Fig. 172.
[Illustration]