Up: Glassmaking
How It Is Made
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furnace, where it is placed on end and gradually cooled.
The largest sheets made measure about 7 feet
by 4 feet, but only few workmen are sufficiently skilful to blow the
cylinders required for such sizes. Sheet-glass is classed by the
number of ounces that a square foot of it weighs--"12-oz.," "18-oz.,"
"20-oz." glass.
Blowing and drawing and shaping
by hand are used in combination for such things as wine glasses and
vases (Fig. 57), which begin as a bulb, have stems
drawn from the tip by the application of an iron rod, and, after being
detached from the blowpipe, are reheated and shaped by the pressure of a
tool on the free edge. Glass tubes are made by drawing out a bulb
of glass from both ends, the size depending on the speed at which the drawing
is done; glass rods by similarly extending a solid mass of glass.
GLASS-ROLLING
is necessary for the manufacture of very thick sheet-glass, generally
known as plate-glass. The apparatus used is a large flat iron table
over which a roller is run, resting at each end on two strips of iron of
the thickness of the plate required. The width of the
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