Clearfield Republican. [volume] (Clearfield, Pa.) 1851-1937, 1874-10-28
MANUFACTURE OF PLATE
GLASS.

The manufacture of plate glass, as
now conducted by the Thames Plate
Glass Company, at Blackwall, London,
is us follows:
The principal successive operations
necessary to convert mixture in the
pot into n finished sheet of plate glass
are six in number and may be des-
cribed under the heads of melting,
rolling, annealing, grinding, smoothing
and polishing. The pots are of Stour-
bridge clay, made on the premises, and
are filed with the mixture, the chief
ingredients of which are silica, sand
carefully dried, lime, sulphate of soda,
broken with glass and little arsenic.
The sand is obtained from Germany.
After remaining in the furnace for
about sixteen hours, the contents Of
the pot are fit for removal. The mol
ten mass is then run over the surface Of
the rolling table, and the roller passed
quickly over it. The glass commences
to solidify almost Immediately and
while in n thick tenacious condition,
and of rich golden tint, is rapidly
transferred into the annealing furnace.
The rough sheet, as II may now be
termed, is taken from the annealing
furnace to the grinding-room of these
there are several, containing about a
dozen grinding stones, or, more pro-
perly, beds, or tables, upon which the
plate is laid fiat. The grinding frames
consist of wooden boards joined to-
gether and armor plated, SO to speak,
at intervals over the rolling or grind
ing surfaces with strips Of wrought
iron. These strips, when first screwed
on to the frames, are half an inch in
thickness, and when removed measure
less than one eighth inch. The frames
are mounted upon spindle, and asee-
saw, semi-rotary movement, is I'M
parted TO them by shafting running
underneath the beds. They are also
capable of being shifted by simple
slot connection so as TO work over any
part of the surhrcc of the sheet as re-
quired Thegrinding beds are Of stone,
and measure about l6 feet by II feet.
The materials used as the grinding
agents are coarse sand, fine sand, and
emery A jet of water plays on the
surface Of the sheet during the whole
Of the operation.
Between the grinding and polishing
processes there is an intermediate pro-
cess called smoothing, in which two
sheets of glass are employed. One is
laid over the other and caused TO move
over il in manner similar TO that in
grinding Emery is placed between
the two surfaces. On entering the
polishing room, the attention of a visi-
tor is at once arrested by the reddish
tinge of everything, extending TO the
, dresses of the men and women engaged
therein. This is due TO the use Of the
red oxide of iron which is the polish
ing agent. The sheet to be polished
,, ia laid fiat on a table, so as TO be per
! fectly flush with the edges. The rub
bers are of flannel and mounted on Q
frame, which carries them backwards
!, and forwards over the sheet. The
! table, at the same time, has latera
reciprocating motion, so that the whole
K surface of the sheet comes successivcly
n under the action OF the rubben. Th'
; largest plates measure about 10 feet by
It 10 feet and the maximum thickness y
p about Ia inches. One eighth Of an incl
l, is allowed for loss in the opperaton
l. we have described. A nest Of si'
,sl boilers and three vertical steam engines
N two of 20 horse power and one Of Q
10 horse power supply tho necessary INC
{ tive power. 1''ltl 81