The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1874-09-19
Manufacture of Plate Glass.

The manufacture Of plate glass, as nov
conducted by the Thames -Pirte- 6las,
Company, at Blackwell, London, is as fol
lows:
The principal successive operations ne
cessary to convert mixture in the poi
into finished sheet Of plate glass are sis
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 filed with the mixture
the chief ingredients Of which are silica,
sand carefully dried, lime, sulphate of soda
broken white glass, and little arsenic
The sand is obtained from Germany. Af
ter remaining in the furnace for about
sixteen hours, the contents of the pot are
fit for removal. The molten mass is then
run over the surface Of the rolling table,
and the roller passed quickly over it. The
glass commences to solidify almost imme-
diately; and while in thick tenacious
condition, and Of a rich golden tint, is
transferred into the annealing furnace.
The rough sheet, as it may now be termed,
is taken from the annealing furnace to 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 fat, The grinding
frames consist Of wooden boards Joined
together and armor-plated, so 10 speak, at
intervals over the rolling or grinding sur
faces 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 eight inch.
The frames are mounted upon spindle,
and see-saw, semi-rotary movement is
impaired to them by shafting running nm
derneath the beds. They are also capable
of being shifted by a simple slot connec-
tion SO as to work over any part Of the
surface of the sheet as required. The
grinding beds are Of stone, and measure
about 16 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 process
called smoothing, in which two sheets Of
glass are employed. One is laid over the
other and caused to move over it ID man
ner similar to that in grinding. Emery is
placed between the two surfaces On
entering the polishing room, the attention
Of a visitor Is at once arrested by the red
dish tingc Of everything, extending 10 the
dresses Of the men and women engaged
therein. This is due to the use Of the red
oxide Of iron which is the polishing agent
The sheet 70 be polished Is laid fat on a
table, 50 as to be perfectly flush with the
edges. The rubbers are Of flannel and
mounted on franc, which carries them
backwards and forward over The sheet.
The table, at The same time, has lctesal
reciprocating motion, 50 that the whole
surface Of the sheet comes succesaisely
under the action Of the rubbers. The lar
gcst plates measure about 15 fcet hv 10
feet, aud the maximum thickness Il about
1 I inches. One eight Of an inch il allow
Cd for los II Tie operations 70 have d.
c1ibed. 4 nest Of six boilers, and three
vertical steam engines, txo Or 70 horse
power and ono of 60 horse po0pf, supply
The necessary motive power.