1. The appellation of _founder_ is given to the superintendent of a
blast-furnace, and likewise to those persons who make castings either
of iron or any other metal. In every case, the term is qualified by a
word prefixed, indicating the metal in which he operates, or the kind
of castings which he may make; as _brass_-founder, _iron_-founder, or
_bell_-founder. But whatsoever may be the material in which he
operates, or the kind of castings which he may produce, his work is
performed on the same general principle.
2. The sand most generally employed by the founder is _loam_, which
possesses a sufficient proportion of argillaceous matter, to render it
moderately cohesive, when damp. The moulds are formed by burying in
the sand, wooden or metallic patterns, having the exact shape of the
respective articles to be cast. To exemplify the general manner of
forming moulds, we will explain the process of forming one for the
_spider_, a very common kitchen utensil.
3. The pattern is laid upon a plain board, which in this application
is called a _follow board_, and surrounded with a frame called a
_flask_, three or four inches deep. This is filled with sand, and
consolidated with rammers, and by treading it with the feet. Three
wooden patterns for the legs are next buried in the sand, and a hole
is made for pouring in the metal.
4. One side of the mould having been thus formed, the flask, with its
contents, is turned over, and, the follow board having been removed,
another flask is applied to the first, and filled with sand in the
same manner. The two flasks are then taken apart, and the main
pattern, together with those for the legs, removed. The whole
operation is finished by again closing the flasks.
5. The mode of proceeding in forming moulds for different articles, is
varied, of course, to suit their conformation. The pattern is often
composed of several pieces, and the number and form of the flasks are
also varied accordingly. Cannon-balls are sometimes cast in moulds of
iron; and to prevent the melted metal from adhering to them, the
inside is covered with pulverized black lead.
6. Rollers for flattening iron are also cast in iron moulds. This
method is called _chill-casting_, and has for its object the hardening
of the surface of the metal, by the sudden reduction of the
temperature, which takes place in consequence of the great power of
the mould, as a conductor of heat. These rollers are afterwards turned
in a powerful lathe.
7. Several _moulders_ work together in one foundery, and, when they
have completed a sufficient number of moulds, they fill them with the
liquid metal. The metal for small articles is dipped from the hearth
or crucible of the furnace with iron ladles defended on every side
with a thin coating of clay mortar, and poured thence into the moulds.
But in casting articles requiring a great amount of iron, such as
cannon, and some parts of the machinery for steam engines, the iron is
transferred to the moulds, in a continued stream, through a channel
leading from the bottom of the crucible. In such cases, the moulds are
constructed in a pit dug in the earth near the furnace. Large ladles
full of iron are, in some founderies, emptied into the moulds by the
aid of huge cranes.
8. Although the moulders have their distinct work to perform, yet they
often assist each other in lifting heavy flasks, and in all cases, in
filling the moulds. The latter operation is very laborious; but the
exertion is continued but a short time, since the moulds, constructed
during a whole day, can be filled in ten or fifteen minutes.
9. Iron-founderies are usually located in or near large cities or
towns, and are supplied with crude iron, or pig metal, from the blast
furnaces in the interior. The metal is fused either with charcoal or
with pit coal. In the former case, an artificial blast is necessary to
ignite the fuel; but in the latter, this object is often effected in
air furnaces, which are so constructed that a sufficient current of
air is obtained directly from the atmosphere.
10. The practice of making castings of iron is comparatively modern;
those of the ancients were made of brass, and other alloys of copper.
Until the beginning of the last century, iron was but little applied
in this way. This use of it, however, has extended so rapidly, that
cast iron is now the material of almost every kind of machinery, as
well as that of innumerable implements of common application. Even
bridges and rail-roads have been constructed of cast iron.