THE MANIPULATION OF GLASS
GLASS MAKERS’ TOOLS AND MACHINES
The tools used by the glass blowers are few and simple. The greater part
of the crude form is produced by blowing out the hot glass into a
spherical or pear-shaped bulb and regulating the size and thickness by
gathering more or less material. The tools are mainly employed in
finishing and shaping this bulb into the desired form, such as shearing,
forming the neck spout, crimpling, and sticking on the handles to the
various shapes made.
According to the type of the goods manufactured, different manipulative
methods in forming the articles are adopted in various works.
The best English table glassware is mostly hand-made blown ware,
generally entirely executed by the handicraft of the workman without the
aid of moulds to form any part of the articles, and a considerable
amount of skill and practice is necessary before the workman is
competent enough to shape a number of articles exactly to the form of
his model. It is astonishing to notice the skill and precision with
which a workman produces wine-glasses one after another, so uniform that
one cannot trace any dissimilarity between them.
A second class, or cheaper form, of tableware is made by blowing the
sphere or bulb of hot glass within a mould, to give some part, or the
whole form, of the desired article. If only a portion of the intended
shape is thus formed by the mould, it is afterwards finished by hand
with tools. This is the general continental method of working, and has
only been partially adopted by this country for making tableware. Where
a number of articles of one shape have to be produced, this is by far
the most economical method. Glass tumblers, honey pots, and rose bowls
illustrate this class of ware.
Another class of tableware produced by a method of pressing the form is
known as “Pressed glassware.” The hot metal is gathered from the pot and
a portion cut off, and allowed to fall into an iron mould fixed within a
lever press, which carries a plunger fitting within the mould formed to
shape the interior and exterior, with the thickness of the glass as the
intermediate space between them. As the hot glass is introduced, the
workman brings down the lever arm and the plunger presses the hot metal
to shape. The plunger is then released and the mould reversed, turning
out the pressed form of glass, which is then carried away to be
fire-polished or further manipulated with tools before it goes to the
lehr. The case or mould portion is made in two halves, to facilitate the
removal of the hot glass after being pressed. Pressed glass tableware
can be recognised by the presence of seams, showing these divisions of
the mould. Many exquisite designs imitating cut-glass tableware are
executed in pressed glassware. The moulds are a very expensive item, as
there is much tool work in cutting the patterns and refacing them after
prolonged use. In making pressed goods, an oily, carbonaceous liquid is
used to give the moulds some protection and prevent the oxidation of the
iron. This liquid is from time to time applied, as the work of pressing
proceeds, by mopping the interior of the mould with a mop dipped in the
preparation.
Another process in glassmaking is that of bottle-making by automatic
machinery, in which the glass worker does little but gather the
requisite quantity of glass from the pot and place it into the revolving
clips of a bottle-making machine, which does the work of formation, by
the aid of compressed air delivered from a supply main. This is largely
of American introduction, and is the method adopted in making common
bottles. In some cases the bottle neck may be finished by a hand tool
after a mould has done its part of forming the bottle. Modern machines
have been perfected to do the whole work of gathering the metal, forming
the shape, and completing the bottle; a number of arms travelling round
a track carry the mould forms, which alternately dip into water to keep
them cool, open to receive the hot metal, close, deliver a requisite
pressure of air to extend the hot glass within the mould, and then
deliver the bottle on to a travelling belt, which takes them to be
annealed.
In the manufacture of bottles by machines, hand labour is practically
eliminated as far as the actual making of the bottle is concerned. The
bottle-making industry is undergoing great changes by the introduction
of such machinery. In some plants a ten-armed machine will produce
automatically 120 gross of 16 oz. bottles in twenty-four hours, at an
average cost of 1s. 6d. a gross.
Owen’s Bottle-making Machines are of this type. Such machines produce
700 bottles an hour, according to their size and the number of arms
fitted to the machine.
As an illustration of a less complicated bottle-making machine, “The
Harlington” may be described.
This machine consists principally of a table, on which is arranged on
the left-hand side a parrison mould, and on the right-hand side a column
with a revolving table carrying two finishing moulds.
[Illustration:
_By permission of_ _Melin & Co._
“THE HARLINGTON” BOTTLE-MAKING MACHINE
]
Below the table, near the parrison mould, is arranged an air cylinder,
through which a piston runs, operated by a hand lever. On the upper part
of the column, on which revolves the table with the two finishing
moulds, is also arranged an air cylinder operated by a hand lever.
The method of working is now as follows—
A gatherer puts the metal into the parrison mould into which it is
sucked by moving the left-hand lever. Through this operation the head of
the bottle is formed and finished. By reversing the lever, air enters
the parrison, thus blowing the same out to the height of the parrison
mould. The parrison mould is now opened and the parrison hanging in the
head-mould held by the tongues is placed under the blowing cylinder
above the open finishing mould. Now the latter is closed, and by moving
the lever, the bottle is blown and finished. Whilst this last operation
is being effected by a boy, the table is revolved and the previously
finished bottle is taken out and another parrison is made ready to be
handled in the described way. This machine produces 200 bottles per
hour.
=The Glass Blower’s Tools.= The glass maker’s chief tool is the
blow-iron. This is a tube of iron 1/2 to 1-1/4 in. wide and about 4 to 5
ft. long, one end of which is shaped or drawn in so as to be convenient
for holding to the lips, and the other end is slightly thickened into a
pear-shaped form, on which the hot metal is gathered.
In making crystal tableware the workman manipulates the glass he has
gathered on this blow-iron by marvering it on a marver. This is a heavy
slab of iron with a polished face about 1 ft. by 1 ft. 6 in., and 1 in.
thick, supported on a low table. Sometimes this marver may be a block of
wood with hollows of definite forms, in which the workman rotates the
hot glass he has gathered to regulate the form and thickness of the
metal to suit his work before beginning to blow it out into a hollow
bulb.
The pontil is a solid rod of iron of similar length and thickness to the
blow-iron. By gathering a little wad of hot glass on the pontil and
sticking it against the end of the bulb attached to the blow-iron, the
workman can detach the bulb from the blow-iron and hold it by the pontil
to which it has been transferred, and which enables him to work on the
other end or opening in the bulb which is exposed in detaching it from
the blow-iron.
[Illustration:
GLASS WORKER’S CHAIR
]
After re-heating the glass, he may shear it with his scissors or shears,
open it out with his pucellas, crimple it with his tongs, measure and
caliper it, or shape it to a template.
Whilst he is doing such operations he sits in a glass worker’s chair.
This chair has two long extending arms, which are slightly inclined, and
along which he rolls his blow-iron or pontil, with the glass article
attached, working upon the rotating form, turning the iron with one
hand, whilst he uses his tools with the other hand, to shape or cut the
glass to its requisite form whilst it is hot, soft, and malleable.
The shears are like an ordinary pair of scissors, and are used for
cutting the hot glass, or shearing off the tops of bowls and wines to
their proper height.
The pucellas is a steel, spring-handled tool in the form of tongs, which
the workman uses to widen, extend, or reduce the open forms of glass by
bringing pressure upon the grips of the tool whilst applying it to the
hot glass.
The glass maker also uses another form of spring tool in taking hold of
hot glass or pinching hot glass to form. These are the tongs.
The battledore, or palette, is a flat board of wood with a handle, used
for flattening and trueing the bottoms of jugs or decanters, etc.
The chest knife is a flat bar of iron, usually an old file, used for
knocking off the waste glass remaining on the blow-irons and pontils
after use. A chest or iron box is kept for collecting such waste glass
for further use. A pair of compasses, calipers, and a foot rule complete
the glass maker’s outfit of tools.
=Making a Wine-glass.= The manipulations in the manufacture of a
wine-glass will now be described. A common mule wine-glass is formed
from three distinct pieces of glass: (_a_) the bowl; (_b_) the leg;
(_c_) the foot.
A wine “shop,” or “chair,” consists of three men; a “workman,” whose
main work consists of finishing the wine-glass; a “servitor,” who forms
or shapes the bulb; a “foot maker,” who gathers and marvers the glass;
and a boy who carries away and cleans the blow-irons.
The “footmaker” of the “chair” gathers on the end of a blowing-iron
sufficient glass to form a bowl. This is then shaped on a marver until
the required shape is obtained. The footmaker then blows this out to a
hollow bulb similar in size to the pattern to which he is working. When
the bulb leaves the footmaker it is the shape of the bowl of the
wine-glass.
This is then handed over to the servitor, who drops a small piece of hot
glass on to the end of the bulb, and heats the whole by holding it in
the furnace. This serves to make the joint of the two pieces perfect.
The servitor next proceeds to draw out the leg from the small piece of
glass at the end of the bulb, leaving a button of glass at the end of
the leg. The servitor then dips the end of the leg into the molten glass
within the pot and gathers on sufficient glass to form a foot. He
spreads this portion of the glass out to the required shape and size
with a pair of wooden clappers, with which he squeezes the hot glass to
form the foot.
The servitor has now done his part of the work, and the glass is handed
to the workman. It is then cracked off, and the foot caught by a spring
clip arrangement attached to a pontil, called a “gadget.” The workman
now re-heats or melts the top edge of the glass by holding it within the
furnace, and when it is hot he cuts off the surplus glass with a pair of
shears. A line is chalked on at the correct distance from the foot, and
guides the workman in cutting the glass to the proper height. He then
melts the top again and opens it out with his spring tool to the
required shape, after which the glass is taken to the annealing lehr by
the boy, to be annealed.
Other forms of wine-glasses are made, and various methods are adopted,
according to the district and class of workmen.
For instance, the method of making the above common mule wine-glass
varies in different districts. Instead of gathering the metal for the
foot upon the leg of the glass, the workman may drop a piece of hot
glass, which has been gathered by the servitor, on to the button at the
end of the leg, and by means of a pair of wood clappers spread the hot
glass to form the foot.
In another method of making a wine-glass, the stem or leg is drawn out
from the body of the bulb by pinching down a knob at the end of the
glass. The servitor draws the leg out of this knob and knocks off the
extreme end. Meanwhile, the footmaker has been preparing a foot,
gathering a small portion of metal on a blow-iron and blowing it out and
shaping it into a double globule. The end globule forms the foot and the
second merely acts as a support. The footmaker takes these globules, and
the servitor sticks them on to the drawn stem of the wine whilst it is
hot; the blow-iron holding the globules is knocked away, leaving them
adhering to the leg of the wine-glass. The footmaker then knocks off the
second globule at the line between the two and, re-heating the bulb at
the foot of the glass, opens and widens the edges out. The glass then
goes to the workman to be finished in the same way as the common mule
wine-glass.
Many articles of glassware are formed with the aid of moulds. Take as an
illustration the manufacture of tumblers and honey pots. A quantity of
glass is gathered on the blow-iron, marvered, and blown out into an
elongated bulb, which is introduced into a mould divided in two halves,
which open or shut by hinges, a handle being fixed on either half to
facilitate the operation. The interior of the mould is made to the shape
of the article, and as the bulb of hot glass is introduced it is shut,
and the workman blows down his blow-iron and extends the glass until it
expands and fills the space within the mould, giving the complete form
of the article with a surplus of metal just where the blow-iron is
attached to the glass at the top. These tops are then cut off and
finished, either by the workman re-heating the article by attaching the
bottom to a pontil and shearing off the top edges, or the glass is
annealed in its unfinished state and the top surplus portion cut off by
an automatic machine specially constructed for cracking off such goods.
[Illustration:
GLASSWARE BLOWN IN MOULDS SHOWING PORTIONS CRACKED OFF
(_a_) Tumbler.
(_b_) Honey Pot.
]
Such machines consist of a set of revolving tables upon which the glass
articles are centred, and each in turn revolves in front of a thin,
pointed, hot jet of gas flame, which impinges on the glass at the height
at which the glass is to be cracked off. After one or two revolutions in
front of this hot pencil of flame, it is removed, and, by applying a
cold steel point so adjusted as to touch the part where the jet has
heated the glass, a chill is imparted which causes the upper portion of
the glass to crack away in a clear, sharp line round the glass. This top
portion of surplus glass is thrown aside and returned to the furnace for
re-melting as cullet.
The tumbler or honey pot is then conveyed to another machine which
fire-polishes the edges to a smooth finish.
This machine consists of a circular revolving frame carrying small
supports, which themselves rotate on their own centres. Upon each
support an article is placed to be fire-polished and the frame carries
them round, and they travel into another section of the machine, passing
under a hooded chamber, which is heated by a fierce jet of flame. The
jet of flame, which is localised on to the top edges of the tumblers or
other goods passing through the hood, gives just sufficient heat to melt
and round off the sharp edges of the glassware where they have been
cracked off by the previous machines. By using these machines in this
way labour is considerably economised, and as many as 300 or more
articles an hour can be cracked off and fire-polished with unskilled
labour.
These machines are extensively adopted in the manufacture of electric
light bulbs, shades, lamp chimneys, and tumblers.
Moulds are usually opened, shut, and dipped by boys, but in up-to-date
glass works an automatic machine called a “Mechanical Boy” is used. With
this machine, the mould is operated at the desire of the workman and not
at the desire of the boy. The output is considerably expedited by the
use of these automatic devices for opening and shutting the moulds.
It is obvious that whatever the shape of the mould, or whatever the
design within the case, the glass takes the impression and retains it in
after working. In this way, square sections, fluted indentations, or
raised bosses can be formed with facility and regularity.
[Illustration:
_By permission of_ _Melin & Co._
VERTICAL CRACKING-OFF MACHINE
]
The Glass Workers’ Union consider that the introduction of machinery
deprives men of their independence and right to work, but as yet the
glass blowers have been always fully occupied with useful work about the
factories in which such machines have been introduced, so it cannot be
said that they have been forced to be idle.
The advantages possessed by these automatic machines in their larger
output at so much less cost compared with hand labour is the great
factor in inducing their adoption; and in these days of progress and
competition such machines enable the glass manufacturers to cope with
the increasing demand and go far towards bringing a factory up to date
and making it well equipped.
Manufacturers should certainly turn their attention to these mechanical
methods, as their use is quite general on the Continent and in America,
and by their use the metal can be worked out of the pots or tanks much
more quickly, increasing considerably the turnout or capacity of the
furnace against the fuel consumption. Much of the glassware imported
into this country is composed of such articles as would have been
manipulated by machines, and, unless a similar method of manufacturing
them is adopted here, we cannot hope to compete with other countries in
supplying our own needs. In the writer’s opinion, it is mainly due to
the adoption of machinery for producing glassware that the continental
people have been enabled to undersell us in our own market, and English
manufacturers could produce at a much cheaper rate if they would only
adopt similar methods of manufacture and the gas-fired furnaces as used
abroad.
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