[Illustration: WORKSHOP.]
Tin is never found existing in an uncombined or native state. Tin ore
occurs most abundantly in Cornwall and Devon, the mines of these counties
having been celebrated for this metal from very ancient times. The
district in Cornwall where tin mines are most abundant is termed the
“Stannaries.” The Prince of Wales for the time being derives a large
income from the mines, and is termed Lord Warden of the Stannaries. The
word “Stannaries” is derived from the Latin _stannum_, tin. The amount
of tin ore annually obtained from the Cornwall and Devon mines amounts
to 11,000 tons, which, at the average value of £63 per ton, is worth
£693,000. This ore yields about 7,000 tons of the metal, having an
average value of £119 per ton. About four-fifths of all the tin raised in
the world is produced in these mines. The ore is a heavy, hard, brittle,
and usually dark brown mineral, which occurs chiefly in granular masses
of various sizes. These grains are obtained in mines, where they occur in
veins mixed with other minerals, and also from the beds of streams, where
they have been washed out of the soil by the action of running water. In
the former case they are termed tin stone; in the latter stream-tin.
Tin is obtained from the ore by first breaking up the latter, whilst a
current of water flows over it and carries off the impurities, which are
lighter, and therefore more readily borne away than the heavier tin ore.
After being thus freed from the admixture of other minerals, the ore is
usually roasted or burned, to drive off any traces of sulphur it may
contain; it is afterwards heated to redness with blind coal or culm, and
a small portion of lime, when the melted metal separates from the dross,
and runs into cavities prepared for its reception. It is afterwards
refined by being remelted, and other impurities separated, which either
sink or float on the surface. The purest metal is yielded by the ore
called stream-tin, which is smelted with charcoal instead of coal. If
a block of tin thus obtained is heated slightly, and then allowed to
fall from a height, it separates into a number of prisms which adhere
together in pyramidal masses. In this state it is termed grain-tin. Tin
is a silvery-white metal possessed of a high degree of metallic lustre.
It is sufficiently soft to be cut with a knife, and may be readily bent,
when it gives out a peculiar crackling noise; if repeatedly bent and
straightened, it becomes hot from the friction of its particles with one
another, and ultimately breaks. It is inelastic and moderately ductile,
but very malleable, the thickness of tin-foil being about one thousandth
part of an inch. It has but little tenacity, a wire of one-tenth of an
inch in diameter not being able to support a heavier weight than 49 lbs.
Tin is the most easily melted of all the common metals, and it
possesses the valuable property of not rusting when exposed at ordinary
temperatures to the conjoined action of air and water, or even to weak
vegetable acids. Tin, in a pure state, is seldom employed; but in
combination with other metals it is a substance of great value. Its most
important uses depend on its power of resisting the action of air and
moisture; it is therefore largely employed for protecting the surfaces of
copper and iron, that rust so readily.
Tin plate, or more properly tinned plate, which is so largely employed in
the manufacture of saucepans, coffee-pots, tea-kettles, &c. by the tinman
is not, as its ordinary name seems to imply, made of tin, but is formed
of the best sheet iron, rolled out to the required thickness, and coated
on each side with a layer of tin. Copper vessels ought to be invariably
tinned inside, to prevent the rusting of the copper by the action of
acids. Tinfoil is largely employed for the purpose of preserving moist
articles from becoming dry, and is used instead of paper for enclosing
fancy soap, chocolate, and other substances of a similar nature. It is
also extensively used in the manufacture of looking-glasses, and is
sometimes placed behind paper-hangings to exclude the damp of the walls.
The most important alloys into the composition of which tin enters are
bronze, pewter, bell-metal, and solder. Tin dissolved in acids is largely
employed by dyers in fixing or rendering permanent various colours used
in dyeing. The preparation termed putty powder is a rust of tin, obtained
by exposing the melted metal to the air; it is employed in polishing
metals and other articles.
[Illustration: Mallet. Soldering Iron. Hammer. Block Hammer.]
The tinning of the inner surfaces of cooking utensils and other vessels
of capacity is effected by scouring the surface until it is perfectly
bright and clean; then heating the vessel, pouring in some melted tin
and rolling it about, and rubbing the tin all over the surface with a
piece of cloth or a handful of tow; powdered rosin is used to prevent
the formation of oxide. Bridle bits, stirrups, and many other small
articles, are tinned by immersing them in fluid tin. Tin-plate working,
or the forming sheets of tinned iron into a variety of useful vessels and
utensils, is carried on by means of bench and hand _shears_, _mallets_,
and _hammers_, _steel heads_ and _wooden blocks_, _soldering irons_ and
_swages_. In the formation of a vessel, the first operation is to cut the
plate to the proper size and form with shears, and, when the dimensions
of the article require it, to join them together, which is done either
by simply laying the edge of one plate over that of the other, and then
soldering them together, or by folding the edges together with laps and
then soldering them. Similar joints are required when gores or other
pieces are to be inserted, and also at the junction by which a cylinder
is closed in. The usual method of forming laps, bends, or folds, for this
or other purposes, is to lay the plate over the edge of the bench and to
bend it by repeated strokes with a hammer; but a machine is sometimes
used for this purpose.
[Illustration: Straight Snips. Scotch Snips. Large Shears. Bent Snips.]
After a tin vessel has been rounded upon a block or mandril by striking
it with a wooden mallet, and the seams finished, all its exterior edges
are strengthened by bending a thick iron wire into the proper form,
applying it to what would otherwise be the raw edges of the metal, and
dexterously folding them over it with a hammer.
[Illustration: Two-handed Wrench. Soldering Pile. Pudding Stake. Punches.
Hatchet Stake. Tongs.]
A superior kind of tin ware, commonly known as block tin ware, is
carefully finished by beating or planishing with a polished steel
hammer upon a _metal stake_. The process of swaging is resorted to as a
ready means of producing grooved or ridged borders, or other embossed
ornaments. This process consists in striking the metal between two steel
dies or swages, the faces of which bear the desired pattern, and are
made counterparts of each other. Many ornamental articles are produced
by embossing or stamping tin plate, in the same manner as other metallic
sheets, with a fly-press or other machinery. Cheap coffin-plates are
manufactured at Birmingham in this way; and these and similar articles
are sometimes lacquered, painted, or japanned. Tin forms the principal
ingredients in various kinds of pewter and other white-metal alloys,
which are manufactured into domestic utensils by casting, stamping, and
other processes.
[Illustration: Chisels. Charcoal Stove. Polishing Anvil.]
Britannia metal is a mixture of tin, antimony, copper, and brass, which
is melted, cast into slabs, and rolled into sheets. The principal use
of this metal is for candlesticks, teapots, coffee-biggins, and other
vessels for containing liquids. The feet of candlesticks, the bodies
of teapots, and other articles containing embossed work, are stamped
between dies; while articles of a more globular shape are stamped in two
or more pieces, and afterwards soldered together. The sheet metal has
a ductility which enables it to be bent into various curved forms by
pressure on a model or core: this process is called _spinning_.
[Illustration: Funnel Stake. Punches. Horse. Punches. Bick Irons. Crease
Iron.]
Many small vessels, spoons, and other articles, are cast in an alloy
somewhat harder than that which is rolled into sheets. Most of the tools
employed by the Tinman are the _irons_, _stakes_, and _bickers_, on which
the tin is hammered into proper shape, with _shears_ for cutting, the
_punches_ for piercing holes, and the _soldering iron_ and _charcoal
stove_ for making joints.
[Illustration]