well to tap the drawing-rod lightly
with another and larger rod, striking it in all directions and
thus loosening the sand slightly from the pattern. Some molders
tap the pattern gently when withdrawing, as shown at H, in order
to loosen any sand which has a tendency to stick.

After drawing the pattern, place the cope back on the drag, as
shown at J. Place a brick or other flat, heavy object on top of
the mold above the pattern, to prevent the pressure of the melted
metal separating the two halves of the mold, and then pour.

** III- Melting and Pouring [98]

Having prepared one or more molds, the next operation is that of
melting and pouring. An ordinary cast-iron glue-pot makes a good
crucible and can be easily handled by a pair of tongs, made out of
steel rod, as shown in the sketch. In order to hold the tongs
together a small link can be slipped on over the handle, thus
holding the crucible securely.

A second piece of steel rod bent in the form of a hook at the end
is very useful for supporting the weight of the crucible and
prevents spilling the molten metal should the tongs slip off the
crucible. The hook is also useful for removing the crucible from
the fire, which should be done soon after the metal is entirely
melted, in order to prevent overheating. The metal should be
poured into the mold in a small stream, to give the air a chance
to escape, and should not be poured directly into the center of
the opening, as the metal will then strike the bottom hard enough
to loosen the sand, thus making a dirty casting.

[Illustration: Fig. 4 -Pouring the Metal]

If, after being poured, the mold sputters and emits large volumes
of steam, it shows that the sand is too wet, and the castings in
such cases will probably be imperfect and full of holes.

A mold made in the manner previously described may be poured with
any desired metal, but a metal which is easily melted will give
the least trouble. One of the easiest metals to melt and one which
makes very attractive castings is pure tin. Tin melts at a
temperature slightly above the melting point of solder, and,
although somewhat expensive, the permanent brightness and
silver-like appearance of the castings is very desirable. A good
"white metal" may be made by mixing 75% tin, 15% lead, 5% zinc and
5% antimony. The object of adding antimony to an alloy is to
prevent shrinkage when cooling.

A very economical alloy is made by melting up all the old
type-met