Of Copying By Stamping





128. This mode of copying is extensively employed in the

arts. It is generally executed by means of large presses worked

with a screw and heavy flywheel. The materials on which the

copies are impressed are most frequently metals, and the process

is sometimes executed when they are hot, and in one case when the

metal is in a state between solidity and fluidity.



129. Coins and medals. The whole of the coins which circulate

as money are produced by this mode of copying. The screw presses

are either worked by manual labour, by water, or by steam power.

The mint which was sent a few years since to Calcutta was capable

of coining 200,000 pieces a day. Medals, which usually have their

figures in higher relief than coins, are produced by similar

means; but a single blow is rarely sufficient to bring them to

perfection, and the compression of the metal which arises from

the first blow renders it too hard to receive many subsequent

blows without injury to the die. It is therefore, after being

struck, removed to a furnace, in which it is carefully heated

red-hot and annealed, after which operation it is again placed

between the dies, and receives additional blows. For medals, on

which the figures are very prominent, these processes must be

repeated many times. One of the largest medals hitherto struck

underwent them nearly a hundred times before it was completed.



130. Ornaments for military accoutrements, and furniture.

These are usually of brass, and are stamped up out of solid or

sheet brass by placing it between dies, and allowing a heavy

weight to drop upon the upper die from a height of from five to

fifteen feet.



131. Buttons and nail heads. Buttons embossed with crests or

other devices are produced by the same means; and some of those

which are plain receive their hemispherical form from the dies in

which they are struck. The heads of several kinds of nails which

are portions of spheres, or polyhedrons, are also formed by these

means.



132. Of a process for copying, called in France clichee. This

curious method of copying by stamping is applied to medals, and

in some cases to forming stereotype plates. There exists a range

of temperature previous to the melting point of several of the

alloys of lead, tin, and antimony, in which the compound is

neither solid, nor yet fluid. In this kind of pasty state it is

placed in a box under a die, which descends upon it with

considerable force. The blow drives the metal into the finest

lines of the die, and the coldness of the latter immediately

solidifies the whole mass. A quantity of the half-melted metal is

scattered in all directions by the blow, and is retained by the

sides of the box in which the process is carried on. The work

thus produced is admirable for its sharpness, but has not the

finished form of a piece just leaving the coining-press: the

sides are ragged, and it must be trimmed, and its thickness

equalized in the lathe.





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