Year: 1869

A PANE OF glass is not complicated
structure. Were an inventor, however,
called upon to devise a method of making
window glass, having no previous ac-
luaintance with the subject, the method
In use would seem to be the very last he
would be likely to hit upon. It is usual
% speak of common window glass as be-
ing blown. To one unacquainted with
The mode of its manufacture, the term
blown contains q very imperfect idea of
Il. It is true that blowing is q large and
important part of the operation, but it
would be impossible oproduce fiat pane
Of glass by blowing alone


There are three ways in which fiat ta-
bles or plates of glass may be obtained,
one Of which does not involve blowing at
all. Glass made by the latter process is
called plate glass. The glass made by
the two systems which require blowing
are called respectively "crown glass and
cylinder glass" terms derived from Pc
culiaritiea in the methods of producing
them. We shall first describe the method
of producing crown glass. ,...


The arrangement of the furnaces for
glass has already been de-
scTibed. The workman takes up on the
end of his pipe q large mass of glass by
successive operations exactly as described,
except that for making crown glass he
takes up a much larger weight. He also
rolls it upon the "marver" in the same
manner as he would for making bottles
but in the present operation greater care
is required to prevent the occurrence of
inequalities, as the mass of plastic glass
IN nN VSNVNnh Iawn.aR unTyfv,aa ,nI kn |
ball upon themarver until it assumes the
shape of pear, it is next softened in a
small furnace, and again rolled en- the
marver to correct any inequalities that may
have formed during the latter heating, and |
at the same time to collect the greatest |
mass of glass at the extreme end, techni- |
cally called the "bullion." The bulk is |
now further extended by blast from the |
lungs Of the workman, 1t being meanwhile |
supported by resting the pipe upon
horizontal bar, called the bullion bar
until it assumes nearly the form of |
sphere In some instances the "bullion |
bar Is dispensed with, other equivalent |
apparatus being substituted for it. Its use
is to aid the workman in rotating the
bulb, SO as to keep it as nearly as may be
to the globular shape.


It is next taken to the bottoming hole. |
This is circular hole in furnace, before
which, at short distance, is built up a
screen of mason work, which extends far
enough to protect the workman from the
heat His face Is also protected by mask,
having apertures with glass plates to per-
nit his seeing his work. The pipe with
Its expanded bulb is laid across a hook
projecting from the screen of mason work.
Here the bottom of the bulb (bullion) is
exposed directly to a high heat, and the
pipe being rapidly rotated by the work
man, the centrifugal force thus generated
soon reduces the bulb from the form of
globe to that of q prelate spheroid-that
is, it spreads laterally until the side oppo-
site the lre becomes nearly fiat. An as
sistant now attaches to the centre Of the
side opposite the pipe an iron rod called
"pontil" or "punty," so that it shall
stand as nearly as possible in the axis of
rotation. The first workman then imme.
diately detaches the pipe by touching the
neck of hot glass with cold iron Wetted
with water. The side to which the pipe
has hitherto been attached is now pre-
sented to the furnace. Rotation being
continued, the glass begins to expand, the
hole left by the detachment of the pipe
becoming larger and larger, until finally
the whole bulb suddenly expands into a
single fiat table. Before this result is at.
tanned, however, 1t becomes necessary to
remove the bulb to large furnace called
the flashing furnace which has an
opening similar to the bottoming hole"
except that it is larger. The glass has
now the form Of fat circular plate, but


at the point where the punty is attached


there will be left upon 1t projection


called the "bull's eye" In order that the


form Of the plate may not be altered, rota.


tion is kept up until the glass is sufficient


ly cool to support itself 1t is then taken


upon large iron fork by another assist


ant, and, the punty being cracked of, the


plate is carried to the annealing furnace


where it remains twenty -four hours. Af


ter the annealing, the glass may be cut


into proper sizes and packed. 'H3e t'


The above outline gives but a faint idea


OF the skill required to produce crown


glass Necessarily q description Of all the


minor manipulations requiring the great


est dexterity hayesbeen omitted. Enough,


however, has been said to give the reader


correct ideas Of the general principles Of
the method. Grown glass is not manufac-


tured now in this country or In Europe


as extensively a. cylinder glass.


I In the manufacture Of cylinder glass


the blowing extends only 80 far as to. pro


duce . cylinder open at both ends, Ia


fact, the blowing Is, during the entire pro.


cess, accompanied by manipulations Of q
| peculiar character; blowing alone would
| not produce the desired result The fur.


mace holes are somewhat elevated, and


platforms extend out from the base Of the


furnace, one from each hole or pot, upon


which the Wprkmen stand. These plat


forms are Of considerable length, and have
Ipits Of considerable depth dug between


themto permit the workmen to swing the


bulb during the process Of elongation


The manipulations are the same as fol


crown glass up to the point where tht
globe is expanded, and have 30 far beer


already described. When the blast Is frs


forced into the plastic glass, the expansion


takes place in That portion Of the pear


shaped mass called the neck. The work


man now holds the ball over his head, ant


the weight of The thick portion. of th,


mass presses downthe expaned port ia1ssitn "a


iii 1t assumes the shape 81 tho Asp ot q BOT
Tie, like the large bneh n~sd Dy dIug gglsts Z
/ contain their tins4aress etc. The expand


al sgeing new permitted to cool


whssn Ii does rapidly on account oE iu


shinness, becomes rigid The workman


then commences a complex manin


ulatlon. He blows through the PIN


at the same time he rotaEes Ii Il
keep up the cylindrical form of tht
expanding portion, and also SWINGS th
bail II one q the plts above described
] thuaielengstlng the oyliHden The elas
! as IL becomes thin eools of and become
. rigid, and one of the most difficult part
oT the operation consists ia expanding th
glass 70 the required size at precisely th
i time when Y becomes 80 cool as to renal
. IN the proper form. Whom the walls 3