ancients of the Venetians.* It may be thus described:—a
die being prepared, secured by the ring and handle, A,
metal is gathered and dropped into it, B, and the
matrix, or plunger, C, operated upon by the lever,
&c. D, presses the metal into the required form of
the article. If an overplus of metal be gathered, it thickens the
article throughout; but if too little, it fails to fill up the mould, and
is spoiled. This is a rapid mode of reproduction, but great practice is
required to gather the exact quantity of metal. The chief condition of
success, in getting a polished surface on pressed Glass, depends on the
moulds being kept at a regular temperature, a little short of red heat.
The effect is not so good as pillar-moulding, nor does it anneal so well;
but it is much less expensive. The interior plungers and the outer die
will adhere to the Glass if too hot; and if not at a proper temperature,
will fail in producing a clear transparent surface.
Pinching by moulds is chiefly used for
solid drop-work, spangles, &c. Lumps of Glass made expressly for
drop pinching,† when softened sufficiently by a blast-furnace,
A, are shaped in twin brass dies, affixed to tongues,
B. Arms of chandeliers are pressed also by twin dies,
the upper die being fixed to the plunger, and the under one to the bed
* Various slabs of coloured Glass,
of small sizes, were pressed into metallic dies by the ancients,
as proved by the specimens of embossed and intagliated Glass, of
various patterns, in the British Museum; but no machinery was used by
them in producing any completely pressed hollow vessel or utensil,
at one operation.
† A considerable number of
the Glass drops used for chandeliers, girandoles, and candlesticks,
in England, are pinched from thick tumbler bottoms, or waste glass,
causing a variety of tint, and inferior refraction.