[Illustration: WORKSHOP.]
The very great variety of purposes for which the metal called copper is
used, renders it one of the most valuable productions of this country,
and several very important manufactures would be incomplete without
it, since it is the principal material of which many large vessels are
formed, and is also largely employed as an alloy for other metals.
Although the metal is sometimes found in a pure or native state, its most
abundant ore is that known as copper pyrites, of which there are many
kinds. The most common yellow copper ore is a very abundant mineral,
found in large quantities in Cornwall, Devon, and the Isle of Anglesea,
and is a compound of about equal parts of copper, iron, and sulphur. The
mines of Devon and Cornwall yield more than three-fourths of the copper
obtained in England, or about 190,000 tons of ore in a year, the value of
which is above a million sterling. The amount of copper annually obtained
in the United Kingdom is about 15,000 tons, worth more than a million and
a half of money. About the same quantity is imported into this country
from Chili and Cuba, and a very valuable copper ore is also found at the
Burra Burra mines in Australia.
The copper ores of Cornwall and other parts of the country are generally
shipped to Swansea, where coal is abundant, in order to be separated from
the metal. For this purpose the ore is heated to redness, or roasted in
an open furnace, in order to burn away the sulphur, and the fumes given
out by this process are most pernicious. The ore is afterwards melted
several times to separate the other impurities, which, when fused, float
like scum on the surface of the liquid metal, and are then easily removed.
Copper has a peculiar reddish colour, and will bear a brilliant polish;
its smell and taste are both disagreeable. It is one of the most
malleable of metals, and can be so readily worked by the hammer that it
is beaten out into thin leaves, which, under the name of “Dutch metal,”
are employed in ornamenting toys, &c. in imitation of gilding.
It is also so ductile that it can be drawn out into finer wires than any
ordinary metal, except gold, silver, and iron, and its tenacity is so
great that a wire one-tenth of an inch in diameter will bear a weight
of 175 lbs. This wire is very flexible, and not very elastic, but when
rolled into sheets copper is one of the most elastic, and when struck
one of the most vibratory and loud sounding metals.
If taken into the animal system all preparations of copper are violent
poisons; and, as this metal is directly acted upon by vinegar and other
acids, it should not be employed for making vessels used in cooking or
preparing food.
The easy malleability of copper allows it to be rolled into thin sheets,
which can easily be hammered into any form that may be desired, and it is
this operation which belongs to the trade of the Coppersmith.
Sheet copper is employed in covering the bottoms of ships, to protect
them from the attacks of marine animals; it is also used for coins, which
are punched out of the sheet of metal and stamped with dies, and for
plates on which pictures are engraved; the metal being soft enough to
yield to the tool of the engraver, but yet sufficiently hard to resist
the pressure necessary to print the picture.
As an ingredient in alloys copper is most valuable, especially in bell
metal, which is composed of three parts of copper and one part of tin;
in bronze, which is nine-tenths copper and one-tenth tin; and in German
silver, argentine, nickel silver, and other alloys used for making forks,
spoons, dishes, &c. which are composed of copper, zinc, and nickel. These
are very beautiful alloys, closely resembling silver; but the copper they
contain is liable to be partially dissolved by any long exposure to the
action of acids.
Copper is used in small quantities as an alloy for gold and silver both
in coinage and in plate, to give the requisite degree of hardness. Gold
used for coins, or what is called standard gold, is formed of eleven
parts of pure gold and one part of copper. Being a better conductor
of electricity than any other metal, it is largely employed in the
formation of telegraphic wires; and, as it is not hard enough to strike
fire with flint or grit, it is used in gunpowder mills and magazines
instead of iron.
The processes of casting and rolling copper into sheets are so much like
those already described in the manufacture of iron that they need not be
repeated, but the trade of the Coppersmith is distinct from those of the
workers in other metals, though they mostly consist in forming the sheet
copper into various shapes and utensils by means of _hammers_, of which
the _smoothing hammer_, the _set hammer_, and the _riveting hammer_,
explain their own uses by their names.
[Illustration: Copper Bit. Oval Wedge. Riveting Hammer. Smoothing Hammer.
Cob Hammer. Set Hammer.]
In manufacturing the large vessels with circular bottoms which are so
frequently made of copper, the metal is first cast in a shape resembling
a round spectacle glass, that is to say, a flat cake, thick in the middle
and gradually diminishing in thickness towards the edge. It is then
subjected to the powerful blows of a tilt hammer, the beating being
principally confined to the centre. The effect of this is not only to
reduce the thickness of the copper, but to cause the disc to turn up at
the edges and assume the form of a hollow dish.
[Illustration: Punches. Hand Vice. Cutting Punch. Spanner. Anvil. Shears
for Sheet Copper. Hand Shears.]
Another operation of the Coppersmith is called _planishing_, or hammering
the metal until it becomes more dense, firm, and tough; any one who
looks at the surface of a large copper vessel will see the marks of the
hammer by which it has been planished.
It is by the combined operation of casting, rolling, hammering, and
planishing, as well as by the processes of fastening, either with
_rivets_ or with _solder_, that nearly all copper articles are made.
[Illustration: Plumber’s Iron. Iron Horse. Pouncing Block and Hammer.]
Of the tools used by the Coppersmith, beside those already mentioned,
the principal are _punches_ for cutting or piercing holes, _shears_ for
cutting the sheets of metal, the _spanner_ for turning heads of screws or
nuts, the _anvil_, the _blocks_ and _horses_ for receiving the work in
such a position as to operate on any part where the hammer or the punch
is required, and the _iron_ for soldering. There are five different modes
of forming copper piping out of sheet metal; in the first the edges of
the sheet, which is curved round a mandril, are made to meet without
overlapping, and are joined with hard solder; in the second they overlap
and are united by soft solder; in the third they overlap and are secured
by rivets; in the fourth the edges are folded one over the other, and are
made close and firm by hammering; and in the fifth both edges of the pipe
are turned back and covered with a strip of sheet metal, the two edges of
which are turned in and hammered down.
[Illustration: Wood Horse.]