GLASS Important War Material

A L E X A N D E R S I L V E R M A N , Department of Chemistry, The University of Pittsburgh, Pittsburgh, Pa.

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GASS is an indispensable factor in the winning of World War I I . I t is the

mouth, the ear, t he eye, of the widely scattered Armed Forces. I t is their win­dow, ye t it shields them.

Of all the vibrat ions of radiated waves, t h e unaided eye can detect only those of wave lengths 4,000 to 8,000 A. units, the proport ionate equivalent of one black key (flat) t o the ent ire piano keyboard. Glass devices record or detect all the other waves. The voice has limited volume and range. The t ransmit ter bulb sends in­audible waves a round the world, and radio bulbs receive them and render them audible. And in their armored planes a n d ships and cars, men wage their batt les behind " t r anspa ren t steel". Thus is mod­e r n war conducted.

Optical Glass

Prior to World War I America imported mos t of her optical glass from Germany. O u r indust ry was either affiliated with German industry or almost entirely de­pendent upon it. We had imported po­tassium carbonate (pearl ash) from Ger­many, so when war was declared we were caught short and did not even have potash to make optical glass, though other requi­sites—borax, lead oxide, bar ium com­pounds—were abundan t . For tunate ly these experiences t augh t a valuable lesson. Instead of depending upon potassium compounds from the Stassfurt mines and Germany's beet sugar industry, we devel­oped a n American potash industry utiliz­i n g our natural minerals, and fabricating wi th electricity produced by na tura l water power. Also, the Geophysical Laboratory of the Carnegie Insti tut ion, cooperating wi th the optical industry, developed meth­o d s for producing the desired glasses with t h a t efficiency which characterizes Ameri­c a n enterprise.

The ensuing years ensured success in t h e present conflict. When we entered t h i s war, we could produce all of the com­m o n optical types and had an appreciable reserve of research records which has been precious. Wi th a joint committee on F i r e a n d Optics of t he Army and Navy , a n d with men of experience in government

bureaus and in industry, it was only neces­sary to increase production sufficiently. This was accomplished through competi­tive ambition in industry and through federal subsidization of a vast ultramodern optical glass plant in Parkersburg, W. Va. Not only was optical glass made in con­ventional ways, bu t rapid fabrication re­sulted through rolling and casting by large-scale manufacturing methods in plate glass and pressed glass plants. Fac­tories tha t had never dreamed of making optical glass got yields so perfect t ha t the qual i ty of product seemed incredible. And be it remembered tha t except in plants subsidized by and operated under governmental direction, the manufacturer had to conduct his own experiments and submit satisfactory samples before he could get a government order. This as­pect of optical glass manufacture will some d a y bring to light a combination of pa­triotism, pluck, enterprise, and sacrifice on the par t of glass producers tha t few of us

have even imagined. There were two ways of increasing optical glass production quickly: one, to convert existing factories in other glass fields to the painstaking production of optical meta l ; two, to sub­sidize a n d construct exclusive optical plants. T h e former came largely through risks t a k e n by the manufacturers, many of whom did not succeed, and suffered losses. T h e successful ones, with the ex­pansion of our already-existing optical glass indus t ry and completion of the government plant , have more t han met our minimal requirements.

What is this optical glass? An ordinary lens or a prism? Definitely not. We have well outfi t ted trucks in all wrar zones for ophthalmic, optometric, and complete lens and o ther optical fabrication service. Also there is motion-picture equipment for instruction and enter ta inment . In Amer­ica, besides the more common crowns and flints, m a n y special glasses have come into being. The re are the silica-free glasses like the zinc-cadmium-aluminum phos­phates, a n d others, some of whose com­positions have not ye t been disclosed. These h a v e a n appreciably greater index of refraction and lower dispersion. T h e y have extended the field of wide angle pho­tography which has served aviation so well. Accuracy and definition are essential

Light bulbs that generate heat rays bake enamels on armored cars and trucks by radiation

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A startling contribution to Wor ld War M is spun glass for insulation, holding heat in huts for the Armed Forces in the Arct ic, and keeping men cool in armored cars in the tropics

in plotting targets. Optical glass and op­tical instruments have given these.

We need glass for telescopes and micro­scopes, for lighthouses, for binoculars, bomb and gun sights, range finders, peri­scopes, cameras, and projectors. This is colorless glass, transparent t o radiations which are visible to the unaided eye. We have "smoke" glasses, but we also require colorless and colored glasses, transparent or opaque to special radiations. A few examples will illustrate these types. There are spectacle or goggle lenses that cut out ultraviolet, others that cut out infrared. In welding goggles there is a low trans­mission of white light with absorption of heat rays. Red aviation goggles ensure better visibility through fog and haze. Certain dichroic glasses accentuate green or red objects, increasing definition. Polaroid goggles eliminate blinding glare.

But optical principles carry farther. There are lenses and enclosing globes of various designs and sizes. These may meet the requirements of the U. S. Army or Navy , or may be supplied according to British specifications. There are the colored glasses which are employed for flood-lighting and camouflage. The spec­tral transmission is fixed. Red, green, and blue units of various types must possess definite total absorption limits and trans­mit within certain limits a t fixed wave lengths. There is a variety of reds, greens, ;and blues depending on the use, or on the government bureau which establishes the specification.

Glasses are in use which absorb prac­tically a l l visible radiations and transmit only ultraviolet; others absorb all visible light and transmit only infrared. X-ray bulbs transmit the shortest waves. In bulbs used for sunbathing, visible ultra­violet a n d infrared go through the glass, while in heat lamps the visible and infra­red pass- T h e bulbs used i n radio trans­mission, in wireless telephony, and in radar are included in the special types.

Some glasses are clear ; others are etched or sand-blasted. I n the optical lens field, etching has played an important role. Fluorides and hydrofluoric acid have been applied to polished surfaces to reduce re­flection losses. A clear glass, untreated, reflects about 8 per cent of incident light from i t s two surfaces. Increase the num­ber of surfaces, as in a composite lens sys­tem, a n d light losses may total 50 per cent or more. The production of molecular nonreflecting films on the surfaces of com­pound lens parts may almost double light transmission and result i n much greater speed in. photography.

Chemical Glassware

Before World War I we made an alkali-resisting glass, and during the war a num­ber of manufacturers of lamp chimneys and coffee percolators tried their heat-resisting glasses for laboratory purposes. They worked pretty well but did not equal

the old Jena and Triuringian glasses that had been imported regularly prior to the war. Then came the American experi­ments with high borosilicate glasses, cor­rosion, thermal, and shock-resistant. These products largely eliminated foreign competition. Completely to stop this, the Government discontinued duty-free im­portation privileges which had been granted to colleges and universities. For awhile selfish dealers capitalized on the profits of cheap foreign labor and tried t o compete with American manufacturers of laboratory glass. Quality won, and with few exceptions scientific America was inde­pendent of European markets long before World War II. We still imported specially constructed instruments, b u t these, too, are now made here.

Scientific glassware is not limited to laboratory test tubes, beakers, and flasks. Special compositions permit the passing or absorption of certain rays so that fermen-ation and other reactions m a y be acceler­ated or retarded at will. T h e glasses may be colorless or colored. One red glass en­sures the stability" of vitamin C during assay. Green glasses absorb infrared. Clear glasses transmit ultraviolet; in fact, transmission in this region may range from the near ultraviolet of sunlight to the shorter wave transmissions of very high silica glasses and transparent fused quartz. The thermal-shock resistance of the last-named glasses permits the arrest­ing of high-temperature réactions by sud­den chilling, for it i s possible even to place these glasses on i ce and impinge an oxy-acetylene flame on the interior.

High-silica and transparent fused quartz tubes arid bulbs are used in lamps for sterilizing the atmosphere of operating rooms, for tenderizing meat, and in cold-storage units to prevent spoilage.

The laboratory type of glass has ex­tended its usefulness. Compositions which before the war entered the kitchen as oven doors and cooking ware are made into large cast cylinders for condenser columns in industry. Laboratory tubing has evolved into glass pipe for plumbing either with welded or coupled joints. Transpar­ency ensures cleanliness, prevents con­tamination. The laboratory type of glass goes into pumps in chemical industry where metal would be attacked and con­stitutes parts of other mechanical devices.

Among the last of our "independence" products were microscope slides and cover glasses. The latter tissue films are now successfully blown in huge bubbles, gaged and trimmed into small disks in several American factories. And they meet ex­acting specifications.

To prevent the loss of entire units, many interlocking and replaceable parts have been designed for chemical apparatus. These effect economy and afford variety i n equipment design and assembly.

Glass tubing furnishes the thermometer t o record body temperatures as well as those surrounding ground, marine, and air forces. A new annealing process greatly reduces the time required for making ac­curate thermometers. Thermometric con­trol of plant and process ensures uniform­i ty and production constancy.

The tube and glass plunger make up the hypodermic syringe, and glass ampoules and sealed tube vials store serums and antitoxins for the prevention and treat­ment of disease.

Glass ring and contact gages, replacing and conserving metal, ensure dimensional accuracy in cast and machined parte. They do not dent if dropped. If injured they are replaced as any imperfect gage, metal or glass, should be.

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Plate and Window Glass This branch of glass manufacture pro­

duces the microscope and lantern-slide glasses as one extreme and the unbeliev­ably thick, clear, transparent bomber noses and peep holes as the other extreme. I t was considered a great achievement when 3-inch and greater thicknesses of laminated polished plate clearly trans­mitted images without distortion, but when curved laminations proved equally accurate, that was a real accomplishment.

Ability to withstand great differences in external and internal pressure permits atmospheric pressure control within planes a t high altitudes, yet ensures visibility.

T h e many applications of standard varieties of plate and window glass, tem­pered or laminated, in trucks and ar­mored cars are too well known to require elaboration. The rolling and casting of special plate for subsequent cutting into optical blanks have been mentioned.

Plate and window glass have contrib­uted their part to factory construction and in the various housing projects.

Small polished plate mirrors, specially designed, now constitute a part of emer­gency kits for the Armed Forces. They ensure the sighting and signaling of rescue planes.

Transparent mirrors permit unseen ob­servers clearly to view and plan war maneuvers. Before the war France pro­duced plate glass heaters with continuous aluminum patterns fused into the glass surfaces. These carried electric current and became hot. The vertical units are now made in America to serve as space heaters and conserve metal which would ordinarily be required for the manufacture of stoves and furnaces.

Structural Glass

Hollow tile was in use before the war. I t has permitted metal conservation in factory and general construction. The greater transmission of light by the struc­tural material has conserved electricity. The insulation against heat loss has made fuel economy possible. An ideal material for air-conditioned units, hollow glass tile has permitted perfect atmospheric control where necessary.

The hollow tiles, while transmitting light, can so diffuse i t as completely to mask factory operations to outsiders when secrecy is required. If transparency is wanted, some tiles now approximate the quality of polished plate.

Fiber Glass

Though known as glass wool a century ago, this baby of the glass industry has probably made the most startling con­tributions of all glass to World War II . I t i s glass wool insulation that keeps men cool in armored cars in the tropics; i t is spun glass that keeps the heat in, in huts and transportation units in the Arctic.

in scrum production, hypo dermic syringes, ampoules, and scaled tube vials o f glass safely store antitoxins, scrums, vaccines

Glass cloth hangs as fire curtains or partitions in war vessels. In the garments and planes of aviators the wool keeps them warm at great altitudes. Properly metal­lized it may be heated electrically. As a casing or flexible tube, or as sheets , glass cloth is an electrical insulator for metals, or a separator in storage batteries. Be­tween glass plates, or imbedded in trans­parent plastic, it is a heat-insulating light-diffuser.

The lightest batting weighs only half a pound per cubic foot. Substituted for old-fashioned insulation, this quality of glass wool reduces the weight of a battle­ship by almost 500 tons and permits the carrying of more men and cargo.

Glass fibers filter blood plasma on the battlefield, and glass sutures stitch the wounds. Glass-cloth tarpaulins, water­proofed with synthetic resins, protect men and machines from snow, rain, mist, dampness. Their rigidity, when specially constructed, ensures accuracy i n maps and firing charts.

Foam Glass Glass which resembles a frozen, froth,

and is largely air in the glass bubbles of the solid froth, may be produced in various shapes, large and small. Its air content makes it a heat insulator, and 5t possesses the advantage over glass wool that it does not sag or settle; also it is vermin- and rodent-proof.

Foam glass floats. I t is used in life belts, buoys, and life rafts. At home it now con­stitutes the floats in toilet tanks, and is releasing copper and rubber, formerly used in making floats, for -war uses.

Illuminating Were We have long been able to turn night

into day, and it is our good fortune that here we lead the world. T h e 24-hour operation of war plants throughout the

length and breadth of America is victory insurance.

Of bulbs we have a "thousand and one" varieties from the "black light" for fluo­rescent control panels, t o white; from the flashlight bulb to the sealed-in headlight and beyond to the more recent high-power units.

New light bulbs, that generate heat rays, bake enamels and lacquers on armored cars, trucks, and other war products, by radiation.

Of tubes we best know the fluorescent types, so efficient in factory lighting. How many of us know the water-cooled high-silica thousand-watt mercury s'cigaret" lamp, so named from its shape and size; the larger incandescent mercury arcs which produce the billion candle power beams for flooding the skies to locate enemy air­craft?

Less powerful floodlights, with their color filters, serve in camouflage on land and sea.

Sodium vapor lamps ensure safe night travel for war workers. Thermionic bulbs sort their products.

Bottles and Table Ware Bottles are so common that wë pay

little attention to them. The war has changed some of their shapes and their weight, to conserve space and lighten car­goes. But there have been other changes. We require special shapes for penicillin culture. We require special colors and compositions t o protect bottle contents. Perhaps the bottle stores important medi-cinals. Perhaps, under its sealed neck, lies the desiccated blood plasma. Or it may contain sterile distilled water to dilute the plasma before transfusions. Contamina­tion might prove fatal.

Special glasses are required for hand grenades and for containers for war chemi­cals. Our laboratories and factories have produced what was wanted.

Vacuum bottles and flasks store hot coffee for factory worker and warrior alike, and prevent spoilage of stored li­quids in our hospitals in the tropics.

And finally, there are the common tumblers, pitchers, carafes in the mess halls. Many of these are tempered to harden the surface and make them shock-resistant.

Conclusion World War II began with reverses.

With the turn of the tide, forward progress has been steady. Glass in sheet and plate, in lens and prism, in fiber and foam, in lighting bulb and tube, bottle and beaker and flask, provides victory insurance.

BASED on au address delivered September 6, 1943 in Pittsburgh, Fa. , before the Division of Industrial and Engineering Chemistry of the AMERICAN CHEMICAL SOCIETT. Contribution Number 543 from the Department of Chemistry, University of Pittsburgh.

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