314 
Plate Glass. joint e, and are retained by an arch x with pin holes. 
sik eal 
Operation 
of casting. 
PLATE 
CCLXXVI. 
Fig. 16. 
Big, 17. 
Fig. 15. 
Fig. 16. 
Aanealing. 
Fig. 18. 
Squaring 
the plates, 
At one endis a cross handle f, and at the other end two 
handles g,g. These tongs are suspended by four 
chains, from two levers h, h, which, as shewn in Fig. 
17, are fitted on the ends of a bar of iron 7, and through 
the centre of this passes a cylindrical iron pin /, which, 
at the upper end, has an eye to receive the hook of the 
crane rope, which takes up the whole, as shewn in 
Fig. 15. An iron plate é is fixed on the top of the pin, 
to preserve the rope from burning. 
The operation of casting is performed before the 
mouth of the annealing oven, into which the glass plate 
is introduced immediately after casting. These anneal- 
ing furnaces are arranged round the’ building, which 
has the great furnace in the centre, and the table is 
mounted upon wheels for removing it from one anneal- 
ing furnace to another. The crane is also moveable as 
well as a tressel F’, formed for the reception of the roller 
B, when it has travelled over the whole length of the 
plate. The roller B, which weighs 500 weight, is trans- 
orted by a carriage fon wheels. By these means, the 
table and all its apparatus can be very quickly prepared 
for use before any one of the annealing furnaces. 
The cistern being brought to the table Fig. 15, is set 
down at the side, and the tongs (Fig. 16.) being opened, 
the cistern is included between ‘the blades, which are 
shut up and fastened. During this time the surface of 
the glass is skinimed, to remove any scum which may 
float at the top. By means of the crane the cistern is now 
drawn up, and conveyed over the table in the situation 
of Fig. 15. The two workmen, who govern the cistern 
by its handles fand g g, now incline it on the centres of 
the levers 4, h, as shewn in Fig. 17, and pour out a 
stream of liquid glass upon the table AA. Just before 
the roller B, an iron ruler R, which is to form the end 
of the plate, retains the fluid matter from running off at 
the end of the table; and. the workman who manages 
this by its long handle S, withdraws it as the matter 
flows forwards upon the table, so as -to suffer it to ex- 
tend itself over the whole table a moment afterwards. 
When the glass has completely covered the table, the 
roller B is advanced with great regularity and steadi- 
ness. Its great weight presses down and reduces the 
upper surface of the glass to the level of the side ruiers 
a, a. In this operation, some glass will often be forced 
over the edge of the table, in which case it is recei- 
ved into troughs K, placed on the ground for that pur- 
pose. The roller having passed over the whole length 
of the table, is guided into the tressel F at the end. The 
plate of glass thus cast, is not suffered to remain longer 
upon the table than to cool itself, so far that it will not 
pgs by its own weight, and it is then shoved off 
at the end of the table into the annealing furnace, 
before which the table is placed. This is done by 
a tool, Fig.. 18, which has a very long handle for 
two or three men to push it forwards, and the cross 
end is made to receive the end of the plate. The rest of 
the men guide e plate sidewise with irons, and as- 
sist in placing it properly in the annealing oven, which 
does net require a particular description, as it so near- 
ly resembles the oven used by bakers ; but its dimen- 
sions must be sufficient to contain the largest glasses, 
which continue here baking in a moderate heat for fully 
14 days, the heat being at last suffered to die away as 
gradually as possible. When quite cool, the plate of 
lass is withdrawn and carried to.the magazine, where 
it is examined and cut square by a: large diamond, fix- 
ed in a wooden handle, and attached to a block of 
wood to hold it in the proper position, to, cut'in the 
Gass: | 
same manner as the cutter of a plane. ‘This ———— nat : 
drawn over the surface of the glass, cuts so: far, 
very slight blows with a sharp edged hammer on ‘the 
polite side of the glass will beat it 3 and if the frac= 
ture is etd rough, the irregularities are reduced by 
breaking them off with pincers.’ | edi 
The glass plate only requires to be 
lished, which is performed by bedding the plate with 
plaster of Paris, upon a table covered with a large slate 
stone, and laying a smaller plate upon it, which is load. 
ed with weights, and drawn backwards and forwards over 
the great plate: Sand plentifully moistened with water, 
grinds away all the prominences of the glasses, until the 
surfaces of both plates become plane or even. The ups 
per or moveable’ glass is defended by cementing it to 
a strong plank, and upon the back of this the weights 
are laid, which cause the pressure. To give the work- 
men hold of the ‘plate, a large light coach wheel is -— 
laced upon a pin, which projects upwards from the 
Nair of the plank, and two ite. ah ach take hold 
of the rim of the wheel on site sides, alternately 
pushing and pulling it in all directions. As this action 
is transferred by the wheel-to the centre pin, the plate 
is at liberty to move in any direction ; and the work- 
men must take care to vary this every instant, to pre- 
vent the glasses grinding each other into furrows or 
channels. The table — which the grinding is 
formed, is surrounded: 
high, to retain ees water with ape the 
lower plate is cove’ en great ni 8 required, 
the pee plate should be changed ra another up- 
per plate which has been ground on a different table; 
because two plates may grind themselves to a portion 
of a sphere, one becoming concave and the other con- 
_vex; but by changing the grinding plates so as to bring 
two convex or two concave surfaces together, the 
correct each other. When the plates are small, the 
wheel is not used to move the upper one; but the 
board to which the upper glass is cemented has four 
small handles projecting up from it, by which the work- 
men take hold. When, by the grinding, a perfect 
surface is obtained, a finergsand is used to produce 
a smoother surface. A succession of emeries, of dif- 
ferent degrees of fineness, are used after the fine sand, 
and with these the operation of grinding is finished. 
The grinding of both sides being completed, the glass 
is polished by bedding it with plaster upon a flat table, 
and rubbing on the surface with the polisher, which 
is a block of wood, covered on the lower side with 
woollen cloth, The workman keeps it supplied with 
fine polishing powders, as tripoli_ and putty; at first 
using the coarsest, and, towards the end of the - 
tion, the finest. ‘The block. of the polisher for large 
plates is about ten inches square, and has two handles 
projecting from it. But to regulate the pressure, a 
springing pole is put upon the back of the block, and 
being bent to a curve, is supported in the ceiling of the 
workshop. When both surfaces are polished, the glass 
is laid upon a table covered with a cloth, and any de- 
ficiences are removed, by a small polisher applied by 
the pressure of the Ifand without a spring. 
In 
cashire, which we have had occasion to examine, the 
operation of grinding and polishing is performed by 
‘appropriate machinery driven by two large steam en- 
gines. There is nothing very peculiar in the nature of 
this machinery, excepting the ingenious contrivance for 
changing the path of the polisher in advancing and re- 
turning over the plate Forms See Encianp, vol. ix, p. 10. 
y a ledge of about two inches - 
and po- Grind 
the plate glass manufactory at Ravenhead in Lan= 
