How To Write Special Feature Articles / A Handbook for Reporters, Correspondents and Free-Lance Writers Who Desire to Contribute to Popular Magazines and Magazine Sections of Newspapers

by Willard Grosvenor Bleyer

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 supreme.

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.