Fuel for Forge.--Dry fuel gives out far more heat than that which is
damp. As a comparison of the heating powers of different sorts of fuel,
it may be reckoned that 1 lb. of dry charcoal will raise 73 lbs. of water
from freezing to boiling; 1 lb. of pit coal, about 60 lbs.; and 1 lb. of
peat, about 30 lbs. Some kinds of manure-fuel give intense heat, and are
excellent for blacksmith's purposes: that of goats and sheep is the best;
camels' dung is next best, but is not nearly so good; then that of oxen:
the dung of horses is of little use, except as tinder in lighting a fire.
Bellows.--It is of no use attempting to do blacksmith's work, if you have
not a pair of bellows. These can be made of a single goat-skin, of
sufficient power, in skilful hands, to raise small bars of iron to a
welding heat. The boat's head is cut off close under the chin, his legs
at the knee-joint, and a slit is made between the hind legs, through
which the carcase is entirely extracted.After dressing the hide, two
strongish pieces of wood are sewn along the slit, one at each side, just
like the ironwork on each side of the mouth of a carpet-bag, and for the
same purpose, i.e. to strengthen it: a nozzle is inserted at the neck. To
use this apparatus, its mouth is opened, and pulled out; then it is
suddenly shut, by which means the bellows are made to enclose a bagful of
air; this, by pushing the mouth flat home, is ejected through the nozzle.
These bellows require no valve, and are the simplest that can be made:
they are in use throughout India. The nozzle or tube to convey the blast
may be made of a plaster of clay or loam, mixed with grass, and moulded
round a smooth pole.
Metals, to work.--Iron Ore is more easily reduced than the ore of any
other metal: it is usually sufficient to throw the ore into a
charcoal-fire and keep it there for a day or more, when the pure metal
will begin to appear.
Welding Composition for iron or steel, is made of borax 10 parts, sal
ammoniac 1 part; to be melted, run out on an iron plate, and, when cold,
pounded for use.
Cast Steel.--A mixture of 100 parts of soft iron, and two of lamp-soot,
melts as easily as ordinary steel--more easily than iron. This is a ready
way of making cast-steel where great heat cannot be obtained.
Case-hardening is the name given to a simple process, by which the
outside of iron may be turned into steel. Small tools, fish-hooks, and
keys, etc., are usually made of iron; they are fashioned first, and
case-hardened afterwards. There are good reasons for this: first, because
it is the cheapest way of making them; and secondly, because while steel
is hard, iron is tough; and anything made of iron and coated with steel,
combines some of the advantages of both metals. The civilised method of
case-hardening, is to brighten up the iron and to cover it with prussiate
of potash, either powdered or made into a paste. The iron is then heated,
until the prussiate of potash has burned away: this operation is repeated
three or four times. Finally, the iron, now covered with a thin layer of
steel, is hardened by quenching it in water. In default of prussiate of
potash, animal or even vegetable charcoal may be used, but the latter is
a very imperfect substitute. To make animal charcoal, take a scrap of
leather, hide, hoof, horn, flesh, blood--anything, in fact, that has
animal matter in it; dry it into hard chips like charcoal, before a fire,
and powder it. Put the iron that is to be case-hardened, with some of
this charcoal round it, into the midst of a lump of loam. This is first
placed near the fire to harden, and then quite into it, where it should
be allowed to slowly attain a blood-red heat, but no higher. Then, break
open the lump, take out the iron, and drop it into water to harden.
Lead is very useful to a traveller, for he always has bullets, which
furnish the supply of the metal, and it is so fusible that he can readily
melt and cast it into any required shape; using wood, or paper, partly
buried in the earth, for his mould. If a small portion of the lead remain
unmelted in the ladle, the fluid is sure not to burn the mould. By
attending to this a wooden mould may be used scores of times.
[Sketches as described below].
Fig. 1 shows how to cast a leaden plate, which would be useful for
inscriptions, for notices to other parties. If minced into squares, it
would make a substitute for slugs. The figure represents two flat pieces
of wood, enclosing a folded piece of paper, and partly buried in the
earth the lead is to be poured into the paper.
To make a mould for a pencil, or a rod which may be cut into short
lengths for slugs, roll up a piece of paper as shown in fig. 2, and bury
it in the earth: reeds, when they are to be obtained, make a stronger
mould than paper.
To cast a lamp, a bottle, or other hollow article, use a cylinder of
paper, buried in the ground, as in fig. 3, and hold a stick fast in the
middle, while the lead is poured round.
Loose, shaky articles often admit of being set to rights, by warming the
joints and pouring a little melted lead into the cracks.
Tin.--Solder for tin plates, is made of one or two parts of tin, and one
of lead. Before soldering, the surfaces must be quite bright and close
together; and the contact of air must be excluded during the operation,
else the heat will tarnish the surface and prevent the adhesion of the
solder: the borax and resin commonly in use, effect this. The best plan
is to clean the surfaces with muriatic acid saturated with tin: this
method is invariably adopted by watchmakers and opticians, who never use
borax and resin. The point of the soldering-tool must be filed bright.
Copper, to tin.--Clean the copper well with sandstone; heat it, and rub
it with sal-ammoniac till it is quite clean and bright; the tin, with
some powdered resin, is now placed on the copper, which is made so hot as
to melt the tin, and allow it to be spread over the surface with a bit of
rag. A very little tin is used in this way: it is said that a piece as
big as a pea, would tin a large saucepan; which is at the rate of twenty
grains of tin to a square foot of copper.