And the Story of How Sand is Melted into Glass


Remedies for our manifold ills; the refreshment that our infant lips

craved; coolness in time of heat; yes--even tho July 1st has come and

gone--drafts to assuage our thirst; the divers stays and supports of our

declining years--all these things come in bottles. From the time of its

purchase to the moment of its consignment to the barrel in the cellar or

the rapacious wagon of the rag-and-bone man the bottle plays a vital

part in our lives. And as with most inconspicuous necessities, but

little is known of its history. We assume vaguely that it is blown--ever

since we saw the Bohemian Glass Blowers at the World's Fair we have

known that glass is blown into whatever shape fancy may dictate--but

that is as far as our knowledge of its manufacture extends.

As a matter of fact the production of bottles in bulk is one of the most

important features of the glass industry of this country today. The

manufacture of window glass fades into insignficance before the hugeness

of the bottle-making business; and even the advent of prohibition, while

it lessens materially the demand for glass containers of liquids, does

not do so in such degree as to warrant very active uneasiness on the

part of the proprietors of bottle factories.

The process of manufacture of the humble bottle is a surprizingly

involved one. It includes the transportation and preparation of raw

material, the reduction of the material to a proper state of

workability, and the shaping of the material according to design, before

the bottle is ready to go forth on its mission.

The basic material of which all glass is made is, of course, sand. Not

the brown sand of the river-bed, the well remembered "sandy bottom" of

the swimmin' hole of our childhood, but the finest of white sand from

the prehistoric ocean-beds of our country. This sand is brought to the

factory and there mixed by experts with coloring matter and a flux to

aid the melting. On the tint of the finished product depends the sort of

coloring agent used. For clear white glass, called flint glass, no color

is added. The mixing of a copper salt with the sand gives a greenish

tinge to the glass; amber glass is obtained by the addition of an iron

compound; and a little cobalt in the mixture gives the finished bottle

the clear blue tone that used to greet the waking eye as it searched the

room for something to allay that morning's morning feeling. The flux

used is old glass--bits of shattered bottles, scraps from the floor of

the factory. This broken glass is called "cullet," and is carefully

swept into piles and kept in bins for use in the furnaces.

The sand, coloring matter, and cullet, when mixed in the proper

proportions, form what is called in bottle-makers' talk the "batch" or

"dope." This batch is put into a specially constructed furnace--a brick

box about thirty feet long by fifteen wide, and seven feet high at the

crown of the arched roof. This furnace is made of the best refractory

blocks to withstand the fierce heat necessary to bring the batch to a

molten state. The heat is supplied by various fuels--producer-gas is the

most common, tho oil is sometimes used. The gas is forced into the

furnace and mixed with air at its inception; when the mixture is ignited

the flame rolls down across the batch, and the burnt gases pass out of

the furnace on the other side. The gases at their exit pass thru a brick

grating or "checkerboard," which takes up much of the heat; about every

half hour, by an arrangement of valves, the inlet of the gas becomes the

outlet, and vice versa, so that the heat taken up by the checkerboard is

used instead of being dissipated, and as little of the heat of

combustion is lost as is possible. The batch is put into the furnace

from the rear; as it liquefies it flows to the front, where it is drawn

off thru small openings and blown into shape.

The temperature in the furnace averages about 2100 degrees Fahrenheit;

it is lowest at the rear, where the batch is fed in, and graduates to

its highest point just behind the openings thru which the glass is drawn

off. This temperature is measured by special instruments called thermal

couples--two metals joined and placed in the heat of the flame. The heat

sets up an electric current in the joined metals, and this current is

read on a galvanometer graduated to read degrees Fahrenheit instead of

volts, so that the temperature may be read direct.

All furnaces for the melting of sand for glass are essentially the same

in construction and principle. The radical differences in bottle

manufacturing appear in the methods used in drawing off the glass and

blowing it into shape.

Glass is blown by three methods: hand-blowing, semi-automatic blowing,

and automatic blowing. The first used was the hand method, and tho the

introduction of machines is rapidly making the old way a back number,

there are still factories where the old-time glass blower reigns


One of the great centers of the bottle industry in the United States is

down in the southern end of New Jersey. Good sand is dug there--New

Jersey was part of the bed of the Atlantic before it literally rose to

its present state status--and naturally the factories cluster about the

source of supply of material. Within a radius of thirty miles the

investigator may see bottles turned out by all three methods.

The hand-blowing, while it is the slowest and most expensive means of

making bottles, is by far the most picturesque. Imagine a long, low,

dark building--dark as far as daylight is concerned, but weirdly lit by

orange and scarlet flashes from the great furnaces that crouch in its

shelter. At the front of each of these squatting monsters, men,

silhouetted against the fierce glow from the doors, move about like

puppets on wires--any noise they may make is drowned in the mastering

roar of the fire. A worker thrusts a long blowpipe (in glassworkers'

terminology a wand) into the molten mass in the furnace and twirls it

rapidly. The end of the wand, armed with a ball of refractory clay,

collects a ball of semi-liquid glass; the worker must estimate the

amount of glass to be withdrawn for the particular size of the bottle

that is to be made. This ball of glowing material is withdrawn from the

furnace; the worker rolls it on a sloping moldboard, shaping it to a

cylinder, and passes the wand to the blower who is standing ready to

receive it. The blower drops the cylinder of glass into a mold, which is

held open for its reception by yet another man; the mold snaps shut; the

blower applies his mouth to the end of the blowpipe; a quick puff,

accompanied by the drawing away of the wand, blows the glass to shape in

the mold and leaves a thin bubble of glass protruding above. The mold is

opened; the shaped bottle, still faintly glowing, is withdrawn with a

pair of asbestos-lined pincers, and passed to a man who chips off the

bubble on a rough strip of steel, after which he gives the bottle to one

who sits guarding a tiny furnace in which oil sprayed under pressure

roars and flares. The rough neck of the bottle goes into the flame; the

raw edges left when the bubble was chipped off are smoothed away by the

heat; the neck undergoes a final polishing and shaping twirl in the jaws

of a steel instrument, and the bottle is laid on a little shelf to be

carried away. It is shaped, but not finished.

The glass must not be cooled too quickly, lest it be brittle. It must be

annealed--cooled slowly--in order to withstand the rough usage to which

it is to be subjected. The annealing process takes place in a long,

brick tunnel, heated at one end, and gradually cooling to atmospheric

temperature at the other. The bottles are placed on a moving platform,

which slowly carries them from the heated end to the cool end. The

process takes about thirty hours. At the cool end of the annealing

furnace the bottle is met by the packers and is made ready for shipment.

These annealing furnaces are called "lehrs" or "leers"--either spelling

is correct--and the most searching inquiry failed to discover the reason

for the name. They have always been called that, and probably always

will be.

In the hand-blowing process six men are needed to make one bottle.

There must be a gatherer to draw the glass from the furnace; a blower; a

man to handle the mold; a man to chip off the bubble left by the blower;

a shaper to finish the neck of the bottle; and a carrier-off to take the

completed bottles to the lehr. Usually the gatherer is also the blower,

in which case two men are used, one blowing while the other gathers for

his turn; but on one platform I saw the somewhat unusual sight of one

man doing all the blowing while another gathered for him. The pair used

two wands, so that their production was the same as tho two men were

gathering and blowing. This particular blower was making quart bottles,

and he was well qualified for the job. He weighed, at a conservative

estimate, two hundred and fifty pounds, and when he blew something had

to happen. I arrived at his place of labor just as the shifts were being

changed--a glass-furnace is worked continuously, in three eight-hour

shifts--and as the little whistle blew to announce the end of his day's

toil the giant grabbed the last wand, dropped it into the waiting mold,

and blew a mighty blast. A bubble of glass sprang from the mouth of the

mold, swelled to two feet in diameter, and burst with a bang, filling

the air with shimmering flakes of glass, light enough to be wafted like

motes. When the shining shower had settled and I had opened my eyes--it

would not be pleasant to get an eyeful of those beautiful scraps--the

huge blower was diminishing in perspective toward his dinner, and the

furnace door was, for the moment, without its usual hustling

congregation of workers. I made bold to investigate the platform.

Close to me glared the mouth of the furnace, with masses of silver

threads depending from it like the beard of some fiery gulleted

ogre--the strings of glass left by the withdrawal of the wand. The heat

three feet away was enough to make sand melt and run like water, but I

was not unpleasantly warm. This was because I stood at the focus of

three tin pipes, thru which streams of cold air, fan-impelled, beat upon

me. Without this cooling agent it would be impossible for men to work so

close to the heat of the molten glass.

Later, in the cool offices of the company, where the roar of the

furnaces penetrated only as a dull undertone, and electric fans whizzed

away the heat of the summer afternoon, I learned more of the technique

of the bottle industry. Each shape demanded by the trade requires a

special mold, made of cast iron and cut according to the design

submitted. There are, of course, standard shapes for standard bottles;

these are alluded to (reversing the usual practise of metonymy) by using

thing contained for container, as "ginger ales," "olives," "mustards,"

"sodas" and (low be it spoken) "beers." But when a firm places an order

for bottles of a particular shape, or ones with lettering in relief on

the glass, special molds must be made; and after the lot is finished the

molds are useless till another order for that particular design comes

in. A few standard molds are made so that plates with lettering can be

inserted for customers who want trademarks or firm names on their

bottles; but the great majority of the lettered bottles have their own

molds, made especially for them and unable to be used for any other lot.

All bottles are blown in molds; it is in the handling of the molten

glass and the actual blowing that machinery has come to take the place

of men in the glass industry. The first type of machine to be developed

was for blowing the bottle and finishing it, thus doing away with three

of the six men formerly employed in making one bottle. In appearance the

bottle-blowing machine is merely two circular platforms, revolving in

the same horizontal plane, each carrying five molds. One of the

platforms revolves close to the furnace door, and as each mold comes

around it automatically opens and the gatherer draws from the furnace

enough glass for the bottle which is being made at the time, and places

it in the mold. The mold closes, and the platform turns on, bringing

around another mold to the gatherer. Meanwhile a nozzle has snapped down

over the first mold, shaping the neck of the bottle, and beginning the

blowing. As the mold comes to a point diametrically opposite the furnace

door it opens again, and a handler takes the blank, as the bottle is

called at this stage, and places it in a mold on the second revolving

platform. This mold closes and compressed air blows out the bottle as

the platform revolves. As the mold comes around to the handler again it

opens and the handler takes out the finished bottle, replacing it with a

new blank drawn from the mold on the first platform. This operation

necessitates only three men--a gatherer, a handler, and a carrier-off.

It is also much faster than the old method--an average of about forty

bottles per minute as against barely twenty.

A newer development of this machine does away with the gatherer. A long

rod of refractory clay is given a churning movement in the mouth of the

furnace, forcing the molten glass thru a tube. As enough glass for one

bottle appears at the mouth of the tube a knife cuts the mass and the

blob of glass falls into a trough which conveys it to the blank mold. By

an ingenious device the same trough is made to feed three or four

machines at one time. As many as fifty bottles a minute can be turned

out by this combination blowing machine and feeder.

But the apotheosis of bottle-making is to be seen in another factory in

the south Jersey district. Here it is the boast of the superintendents

that from the time the sand goes out of the freight cars in which it is

brought to the plant till the finished bottle is taken by the packer, no

human hand touches the product; and their statement is amply confirmed

by a trip thru the plant. The sand, coloring matter and cullet are in

separate bins; an electrical conveyor takes enough of each for a batch

to a mixing machine; from there the batch goes on a long belt to the

furnace. At the front of the furnace, instead of doors or mouths, is a

revolving pan, kept level full with the molten glass. Outside the

furnace revolves a huge machine with ten arms, each of which carries its

own mold and blowpipe. As each arm passes over the pan in the furnace

the proper amount of glass is sucked into the mold by vacuum; the bottle

is blown and shaped in the course of one revolution, and the mold,

opening, drops the finished bottle into a rack which carries it to the

lehr on a belt. It passes thru the lehr to the packers; and as each rack

is emptied of its bottles the packers place it again on the belt, which

carries it up to the machine, where it collects its cargo of hot bottles

and conducts it again thru the lehr. The entire plant--mixing, feeding,

actually making the bottles, delivery to the lehr, and packing--is

synchronized exactly. Men unload the cars of sand--men pack the bottles.

The intermediate period is entirely mechanical. The plant itself is as

well lighted and ventilated as a department store, and except in the

immediate vicinity of the furnace there is no heat felt above the daily

temperature. The machines average well over a bottle a second, and by an

exceedingly clever arrangement of electrical recording appliances an

accurate record of the output of each machine, as well as the

temperatures of the furnaces and lehrs, is kept in the offices of the

company. The entire equipment is of the most modern, from the boilers

and motors in the power-plant and producer-gas-plant to the packing

platforms. In addition, the plant boasts a complete machine shop where

all the molds are made and the machines repaired.

It is a far cry from human lung-power to the super-efficient machinery

of the new plants; but it is the logical progress of human events,

applying to every product of man's hands, from battleships to--bottles.

* * * * *


(_New York World_)

One illustration, a half-tone reproduction of a photograph of the

exterior of the theater.

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