The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1890-12-31
ABOUT PLATE GLASS.
How That Which Is Cast IL Mnnuract.
urcu and Finished.

How That Which Is Cast IL Mnnufact.
urod and Finished.
The most important form OF cast
glass, and tho most largely produced, is
plato glass, or, as it might moro prop
erly DO called, cast plate glass. This IS
tho woll-known cast, ground and pol
iShcd plate used for windows, mirrors,
otc,. and should not DO COMPOUNDED with
tho blown plato and patent plato. which
arc blown glass. In tho manufacture OF
cast plato furnaces and pots Of the ordi-
nary construction aro used tho melting
pots, howcror, sometimes holding TWO
or two and half tons of hatch. In
French works and in some others. two
forms of pots are used. which arc placed
sido by sido in tho furnace, the ordinary
melting pot, and an auxiliary pot called
y 'curyettc," large enough to hold su''i
cient glass to cast Il shoot of givcn
size. Tho molten glass is ladlcd from
tho pot into the curvottc. allowed to
clear il necessary. aa1 is then cast In
most works, however, tho practice is to
pour or cast directly from tho pot in
which the glass is melted, and in other
cases it is ladled from tho pots TO tho
casting table.
Tho casting-table, formerly made of
bronze, is now made of ono picco of cast
iron, heavy AMI thick. and in width and
length exceeding the Dimensions Of tho
largest sheet glass II is commonly
mounted on wheels, running on {, track
laid down the center of tho casting
room, on each side of which arc tho
annealing ovens.
A heavy cast iron roller tho full
breadth of tho table is arranged TO roll
its whole length by means of spur
wheel on the roller working gearing on
tho side Of the table. Tho height from
the table ut which it rolls. and conso-
quently tho thickness Of tho glass, is
regulated by narrow strips of metal
placed along tho edge of the table,
while the width is determined by what
is known as tho gun" two plates of
cast metal bolted together, adjustable
to tho breadth desired, and moving with
tho roller and before it. All being
ready for casting, a pot filled with tho
molten glass is removed from the mclt-
ing furnace, placed on a truck and run
to tho casting table.
The pot is lifted from the truck bv
means of 4 crane. is suspe ended over ono
end OF tho table and tilted, and tho
semi-fluid mass being poured out tho
roller is moved forward. ilattcning tho
glass and rolling it into uniform
thickness, whilo tho gun" prevents t
from spreading to Il greater width than
is desired. AS soon rs tho plate has
solidiGcd sufficiently to bear moving, it
is laid in tho annealing oven on the
| fiat" to slowly cool. All the opera
tions arc performed with tho greatest
rapidity, that the plato may be as hot
as possible when laid in the oven. Tho
number Of plates that can be put in an
oven varies with tho size of the plates
But ono layer OF those designed
for polishing can bc placed in hit,
consequently largo number of ovens
is needed where large plates arc mado.
These ovens arc largo, shallow brick
| furnaces, with floors rs smooth and level
rs possible, as tho scmi-plastic mass
molds itself into tho uncvenncss. and
any bending OF the plates would make
them valuclcss. AS soon as tho plato is
placed in the oven all tho openings arc
carefully closed, and tho oven is al
lowed to cool gradually to point whore
tho glass may DO safely removed. gen
orally requiring about throo days. The
cast plate as il comes from tho ovon is
rough and Irregular on its surface, con
shutting the rough glass Of commerce.
and in this form it is used for roofs and
floors, and oven windows whore light
without transparency is desired. Amor
lean GlasSworlicr.