The Savannah morning news., 1901-08-28
BLOWN GLASS LAMP CHIMNEYs.
How the Industry Is Carried on i'm n
Great Pittsburg Embellishments.

From the Scientific American.
Perhaps the most important feature
in the manufacture of lamp chimneys
or. indeed. of any form of glassware,
is the mixing of the ingredients. AS
in the case of plate glass, the body of
the mixture consists of a sand which
is as nearly pure silica rock as can be
obtained. The sand is quarried from
silica rock, then thoroughly ground and
sifted through a 40-mesh screen, the
material being received at the works
in the prepared condition. The second
most important ingredient is litharge:
while potash and soda are used as
fluxes. When the above mixture is
used for the best quality of lamp CHM
neys, about so per cent. of the total is
silica. The sand is melted in what is
known as the furnace, a large conicaI
structure which is fired by gas from
beneath and contains some IA to 16
large melting pots, which are nodded
from a specially prepared and very
carefully kneaded pot-clay. The melt
ing pots are generally A inches in their
largest diameter. and so inches in
hight. They are arranged in a circle
within the furnace, each one opposite
a door. 1t takes "a hours to melt the
contents of a pot the size just de-
scribed. Ordinarily the contents are
made up of part of the prepared mix
ture and part "cullett." that is, glass
left over from previous days of opera
tons.
The blowing is done with long iron
tube, known as the blow-pipe. which
has a mouth-piece at one end and is
swelled out and thickened into a bell
mouth form at the lower end. In the
process of blowing, the operator dips
the thickened end into the melting pot
and twist it around until it has gath
cred up ball of molten glass of the
desired. size. The blow-pipe is then
withdrawn from the furnace and the
ball of glass is rolled out
plate and slightly inflated by blowing
through the tube. The blow-pipe is
then handed to the second operator,
who completes the operation of blow
ing. The bubble, If we may so call it,
of glass is thicker and heavier at it's
lower end, and to secure. the elongated
form necessary in lamp chimneys the
operator swings the blow-pipe TO and
fro, thus causing the bubble to stretch
by it's own weight. By thus alternate
ly swinging and blowing he brings the
bubble to the required length, and ap-
proximately to the required diameter,
and then places 1t within a hinged
mold, which is opened to receive it,
either by himself or one of his assist
ants. He then twists the pipe and
blows at the same time, thus pressing
the glass against the inner walls of the
mold. The tube, with the nodded
chimney attached, is then withdrawn
from the mold and handed to another
operator, who, with a pair of spring
tongs, forms the faring top of the
Ian fhtgf1nny and ri <e ch fa-
preston just outside it's base, where IT
is to be broken away from the blow
pipe. Although a large amount of
blowing is done by hand and mouth,
increasing use is being made of what
is known as the Owens blowing ma
chine, which substitutes mechanical for
hand power. This consist of verti-
cal stand, at the base of which is IL
circular table, carrying half dozen of
the hinged molds already referred to.
After the first operator has blown and
elongated the ball of glass to the de-
sired shape, the blow-pipes are placed
in the mold, with the upper end of the
tubes secured in the clamp near the
top of the stand. To each of the tubes
is connected a rubber hose, which is
supplied with air from u small air
pump located on and forming part
of the machine. The table, with its
blow-pipe, is rotated, and air pressure
is applied through the hose, half
dozen chimneys being thus blown and
nodded at the same time.
The chimneys are next to the anneal-
ing furnace. This is constructed with
a metallic belt conveyor that passes
through the furnace from end to end.
The chimneys are piled up thickly up
on this belt and carried through the
furnace. The conveyor moves suffi-
GENTLY slowly TO subject each Chin
ney to the heat of the furnace for from
IL to "a hours. After annealing the
chimney is cut down to length. This
cutting is done by. rotating the Chin
ney horizontally above two fine trans
verse Sits, through which a thin
stream of hot air impinges on the
glass at the point where 1t Is to be
cut through. The strain set up by
this local heating is sufficient to ena-
BILE the girl who attends the machine
to break off the ends with slight
bending pressure. The chimney ends,
after cutting are sharp and rough,
and IL Is necessary to give them the
proper finish. The mouth of the Chin
ney is smoothed by glazing" which
is done by exposing 1t to the blast of
a small gas-fired furnace until fusion
of the edge takes place, the result be-
ing the smooth. rounded edge which
the case of chimneys with crimped
edges, the crimping is done in a spe-
cial machine, which slightly flares and
crimps the edges at one operation.
The base is squared and smoothed
down by grinding it upon circular,
rotating. cast-iron table, whose sur
face is covered with sand and water.
The lamp chimneys are stood on end
in small pockets formed in smaller
disks, answering to the runners" of
a ate-glass grinding machine, and
are loaded with weights to give the
proper pressure. After they have been
ground they are taken to stamping
machine, where the makers name is
stamped on with a hydrofiuoric acid
preparation known as white acid"
The chimneys are next taken to the
labelling and packlng-room, where they
are labeled, wrapped in paper, placed
in separate cardboard boxes. and final
ly delivered to the packers. Such Chin
neys as are not shipped in boxes are
packed loose with straw carefully
worked around them. This packing is
so successful that shipments Of Chin
neys to such distant points as Africa
and AusfraIia reach their destination