Evening star. [volume] (Washington, D.C.) 1854-1972, 1874-10-02
Manufacture of Plate Glass.

TIE manufacture of plate glass, as now COM
Quoted by the Thames Plate Glass company, at
Blackwell, London, is as follows:
The principal successive operations necessary
TO convert mixture in the pot into finished
sheet OF plate glass are six in number, and may
be described under the heads of melting rolling
annealing, grinding, smoothing and polishing
The pots are of StOurbridge clay, made on the
premises, and are filled with the mixture, the
chief ingredients of which are silica, sand care.
fully dried, lime, sulphate of sod broken white
glass, and little arsenic. The sand is obtained
from Germany. After remaining in the furnace
Tor about sixteen hours, the contents of the pot
are lit for removal. The molten mass is then
run over the surface of the rolling table and the
roller passed quickly over il. The glass COM
mences to solidify almost Immediately, and
while in thick tenacious condition, and of a
rich golden tint, is rapidly transferred into the
sRneahDg furnace. The rough sheet, as it NAV
now be termed, is taken from the annealng fur
mace 10 the grinding room; of these there are
several, containing about dozen grinding
stones, or, more properly, beds or tables, upon
which the plate Is laid fiat. The grinding fra mes
consist of wooden boards Joined together and
amor plated, so to speak, at intervals over the
rolling or grinding 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-ei ghth
inch. The frames are mounted upon a spindle,
and see-saw, semi rotary movement is i'm
parted to them by shatting running underneath
the beds. They are also capable of being shifted
by simple slot connection so as to work over
any part OF the surface OF the sheet as req uired
The grinding beds are of stone, and measure
about 10 feet by IL feet. The materials used as
he grinding agents are coarse sand, fine sand
GEd emery. a jet of water plays on the surface
OF The sheet during the whole of the operation.
Between the grinding and polishing processes
here is an intermediate process called smooth
lag, in which two sheets of glass are employed.
one IS laid over the other and caused 10 move
over 1t in manner similar to that in grinding.
Emery is laced between the two surfaces. on
"n'erIng the polishing room, the attention of
ltor is at once arrested by the reddish tinge-
~ ever ything, extending to the dresses OF lne
men ard women engaged therein. This is due
10 the use OF the red oxide OF iron which is the
u';ishing gent. The sheet TO be polished is laid
Ia OF table, so as to be perfectly flush with
he edges. The rubbers are of flannel and
mounted on frame, which carries them back
wards and forwards over the sheet. The table
at the same time, has a lateral reciproc 1ting
mo ion, so that the whole surface of the sheet
comes excessively under the action of the rub
OeTs. The largest plates measure about Is feet
by 10 feet, and the maximum thickness is about
* inches. One eighth of An inch is aIlo wed for
loss IN the operations we have described. A
nest OF six boilers, and three vertical steam en-
giDes, two of 70-hOrse power and one OF 60 horse
power, supply the necessary motive power.