What is usually called tin is, in fact, sheet-iron coated with tin,
and of this tin-plate, kettles, saucepans, &c., are made. The art
of coating iron plates with tin has been practised in England hardly
more than one hundred years. The very best soft iron is used for the
purpose of being tinned. It is rolled out into thin plates, which
are cut by shears into squares of usually thirteen inches long and
ten broad, these plates are dipped into weak acid to clean their
surfaces, then rubbed with sand, and finally washed; they are next
dipped into melted tallow, which preserves their surfaces bright
till they can be used. They are then immersed in melted tin, which
has its surface covered with melted tallow, to keep it from being
converted into oxide. When the plates have remained for a short time
in the tin, they are removed, and the superfluous tin is wiped from
the lower edge with a brush made of hemp, and then cleaned from the
grease with dry bran. The objects gained by coating iron with tin
are, increased beauty of appearance (for when tinned ware is kept
bright, it has almost the color of silver), and a protection to keep
the surface from rusting, and consequently being corroded into holes.
Copper and brass vessels are tinned inside, to prevent the formation
of that poisonous substance called verdigris. The mode of tinning
them is as follows:--They are cleaned inside by means of vitriol, and
then made hot, fine grain-tin and a little rosin being put into them,
and turned about and brushed over the surface with a ball of tow: by
this means, the tin is equally spread over the inner surface of the
vessel.
Tin-tacks, buckles, and other small articles, receive a coating of
tin by being put into an earthen pot together with some grain-tin
and a substance called “sal ammoniac,” and the pot being heated
over a fire sufficiently to melt the tin, is then shaken up till
the articles inside have received a coating of tin.
Iron plates have lately been coated with melted zinc instead of tin,
and the surface thus covered enables them to be used for various
purposes and in situations where they are exposed to the action
of the weather, as on housetops, &c. The plates, thus treated, are
called “galvanised iron,” and they are generally used in a corrugated
form. They withstand the action of the weather very much better than
simple iron plates would, for the latter would be very soon eaten
into holes from rusting.