The Lambertville record. [volume] (Lambertville, N.J.) 1872-1968, 1888-09-12
HOW GLASS Is MADE.
THE PROCESS VARIES WITH THE
DIFFERENT KINDS.

DIFFERENT KINDS.
Material of Which the Melting Pot II
Misunderstanding Done by Metallic Oxides.
Bottles and Window Glass-The Blow
phosphate Glass.
The process Of making glass is exceedingly
interesting, but it is also elaborate and not
free from complication. 1t can. therefore,
only be SET forth in brief and cursory man.
ner. So intricate is the work in some of its
departments that one is puzzled at the pro-
hciency III the art in ancient times The
conclusion Is forced upon us that in this, as
In many other branches Of industry, the
workmen and arti6cers of remote times were
In full command Of many means and appli-
ances Of which we are ignorant The compo-
sition Of which glass is made, not to mention
the fusing and finishing, implies large
amount of chemical knowledge.
What Is this compositionl Generally, it
may be described as consisting of certain
number OF silicates, such as soda, potash,
lime, baryta, magnesia, alumina aud lead,
the co.oring matter being obtained from iron,
niagnesia, cobalt, uranium, copper or gold
The composition, Of course, Is conditioned or
qualified by the kind Of glass which is
wanted The best glass is that which con-
tains the minimum Of uncombined silica.
Bohemian glass Of the harder kind contains
the silicates Of potash and lime in predomi-
nant proportions; Of the softer kinds 1t con-
tains, In addition, notable quantity of the
Eilicate Of alumina. Soda and limo predomi-
nate in French plate. Potash and lead are
the principal silicates In the ordinary flint or
white glass. The lead gives density, soft
ness, feasibility and briliiancy. The exact
proportions, in different cases, of the differ
ent ingredients belong TO the secrets OF the
glassmaker's art
The process of manufacturing varies with
the different kinds of glass. Tho first step in
the process, however, is the Same with all
glass The first requisite is the melting pot,
the making Of which is an art by itself 1t
Is made OF the purest kind Of clay and con-
sists pretty nearly Of equal proportions Of
silicon and alumina, The mass, consisting
also often Of pieces of old pots, is worked up
with water and then laid aside for three or
four months 1t is after that time made into
pots-the work being of the most particular
and iaborious kind-covered at top and bot
tom, with an opening at the side When
thoroughly dried and hardened In the fur
mace, the pots arc filed with the prepared
material, called frit, mixed with a small
quantity of cullet or broken glass. After
some or ten or twelve hours, the heat of the
furnace having been brought to the highest
point, the pots are skinned and the melted
material Is ready for what is called tho jour
ney. During the melting process the color
ing is done by means Of various metallic OK
ides What is called flashed glass Is pro-
duced by another and different process. II
is only specifically colored. Pot metal,
when colored, is colored throughout.
When the material is thoroughly melted
and skinned and made ready for the journey
the work of the blower, or molder, begins.
Bottles and window glass-crown or sheet
are made by tho blow pipe. What Is known
as plate glass and optical glass is cast; and
the glass used for heavy domestic utensils is
the result Of n combined process Of blowing
and casting. The. blow pipe to glassrnaking
plays precisely the same part which is per-
formed by the potter's wheel in the manufac-
ture of earthenware. Il Is an iron pipe
smaller at the mouth end than at the other.
In the manufacture Of Clint glass the pipe is
heated almost TO redness, then inserted into
the pot Of fused glass which adheres to IT,
By turning 1t round the workman gets as
much metal as he requires. He then distends
the glass by blowing through the pipe and
the glass being put into mold he continues
TO blow until tho desired shape is produced.
In this way bottles are made, and also almost
all articles for domestic use. Window glass
is blown into the form of a cylinder. The
ends OF the cylinder are, after cooling pro-
cess, cut of. The cyliner Is then slit by
diamond from end to end, and, being again
heated, 10 is with much care and labor grad
ually hattened out.
Plate glass is made In different manner.
1t Is cast or pressed. When the material Is
melted and ready for use the pot Is lifted out
OF the furnace by means OF forceps and
wheeled up to what is called tho casting
table, where 1t is seized by crane and
tackle, lifted and delicately poised 30 that 1t
can DO easily tilted. Such Ia the necessity for
care and steadiness during the performance
OF this task that the men preserve absolute
silence. After having been poured out upon
the plate 1t Is spread by means Of steel
roller. By means Of successive outpourings
and successive rollings the glass can be mace
to any thickness. Where the machinery Is
less complete the liquid matter Is lifted with
a sort Of dipper, which, like the blowpipe, Is
brought first TO a red heat. As will DO gath
cred from this description, the blowpipo Is
not needed In the manufacturing OF plate
glass. After the glass has been fattened out
and brought TO the requisite standard Of
thickness 1t Is moved to tho annealing room,
and later it Is subjected TO an elaborate pro-
cess OF polishing.
Reference has been made to colored glass
and tho pot glass coloring has already been
explained. Flashed glass, which has not yet
been explained, is thus produced: Tho work
man has two pots in equal conditions of read
iness-the ono containing colorless materials,
the other containing colored material. He
makes his first gatherings from the colorless
glass and the last only from the colored pot.
The consequence is that the glass when fin
ished has a thin skin of colored material on
the outside. For some ornamental purposes
this flashed glass is found specially useful.
Much that Is interesting might be added
here concerning tho cutting, grinding and
engraving of glass; each of which Is prac-
ticed In Brooklyn, and practiced with skill
and success; but these belong to the adjoining
or decorating OF glass rather than to the
making Of It, Much also might be written
concerning glass painting.--"J. L. W." in
Brooklyn Eagle.