Last Updated on 10.05.2017 by hrushetskyy
THE FIRST AUTO MOBILES didn’t come with windshields because they simply didn’t need them. At their top speed the rush of the wind was a gentle breeze cooling to the face and carrying away with it the sometimes none too pleasant odors coming from the engine.
The first use of glass in automobiles was in the lenses of the kerosene or carbide head and tail lamps. The head lights were more like navigation lights permitting other people to see the car than headlights permitting the driver to see a hundred yards or so ahead in the dark.
The next use of glass in automobiles was to cover and protect the instruments on the dashboard a term we still use today with growing inaccuracy and which comes from the curved floorboard of a buggy designed to keep mud from flying into the passenger’s laps while dashing about.
Only when speeds soared above twenty miles an hour did the idea of a windscreen (a term the British use today) to keep dust dirt bugs and mud out of the driver’s eyes come up. The first windscreens were for the driver alone.
The passengers could either wear goggles like an aviator or squint. Only the driver was to be protected from the wind generally by a circular piece of plate glass held in a frame right in front of his face.
Glass the manufacture of which dates back to the Egyptians 2500 years before the birth of Christ was one of the first products to be manufactured in North America several hundred years before; there was a United States of America. It was the first industry to be transported (by the Spanish conquistadores) from Europe. As early as 1535 glass was being manufactured in Mexico and a “glass house” for the manufacture of “glasses and beads” was established in the Jamestown colony of Virginia in 1608.
The first “trial of glass” was sent back to England before the disastrous winter of 1609 which saw the colony just about wiped out (440 of 500 people died) by illness and starvation.
The basic technique of making glass is fairly simple. All that’s needed is a supply of sand (chemically silicon dioxide) limestone (calcium carbonate) sodium carbonate and a good deal of heat to melt it all together. The ingredients are found all over and there is always a need for glass.
The first products of glass were more on the order of ceramics. The raw materials were used in place of clay to come up with a product (a bowl or a glass) with the same use. Gradually man learned to make glass really transparent by using pure basic materials but for a long time he could make it only by pouring it into a mold, Then someone (whether by accident or genius) learned that it is possible to “blow” glass. A gob of it was scooped out of a pot of molten glass on a hollow metal rod. When the craftsman blew down the hollow rod air pressure forced the molten glass outward in a bubble. By turning the rod as he blew down it he could come up with a vessel with even sides and in practically any shape he wanted it.
Then it occurred to someone that it could be used as a covering for windows which were previously either closed with wooden boards or left open to the elements with the only exception being the stained glass windows of churches enormously expensive window coverings made by joining together pieces of flat cast glass with lead. First a large glob of glass was scooped from the pot of molten glass and blown as thin as necessary. Then still in a molten form it was either spun around rapidly and formed into a sheet by centrifugal action or split down the sides and carefully laid on a flat piece of metal to cool. The “bottle glass” so prized by antique collectors which appears to have a bottle bottom in its center is glass made in this fashion. The “bottle bottom” is really the mark left by the “punty” to which the molten glass was attached to be spun around.
“Plate” glass much more expensive was originally made by pouring glass onto a flat surface. After cooling it was polished by a lengthy process involving finer and finer grits.
Glass manufacturing techniques proceeded to improve with the advent of industrial development but the techniques were really nothing more than modifications of the ancient techniques. The man credited with the first really commercial production of sheet glass J. H. Lubbers carried the blowing technique to quite an extreme. Using air pressure he drew cylinders of glass 30 inches in diameter and 40 feet long. They were carried over a forming table split lengthwise down the top and the glass allowed cooling as it flattened against a cast iron table.
The next step was the Foucault process. Molten glass was either heated in or poured into a fire clay vessel. At the bottom of the vessel was a narrow slit. When the slit was opened the molten glass poured out. Workmen grabbed it with tongs and dragged it onto a forming table.
This was about as effective as the slingluff or Pittsburgh process which put a cooling plate or bar into the molten glass. Glass above the plate would be cooled enough so that it could be started out of the pot. When it was a couple of feet above the molten glass it would be solid enough to be put through a series of asbestos faced rollers which would squeeze it to the thickness desired.
The Libbey Owens (later Libbey Owens Ford) Glass Company developed a technique in which molten glass was heated to a precise temperature where it was still molten but cools enough to be drawn from the pot folded over a heated roller and fed into a space between two endless belts. The belts fed it into an annealing furnace some 200 feet long at 100 inches per minute. The annealing furnace gradually cooled the glass as it was moved through and it came out the end in a sheet cool enough to be rigid.
Other machines had been developed by the time an automotive demand for glass came around which automatically made for example light bulb globes continuous tubes of glass (which could be cut off with a machine and made into drinking glasses) and all sorts of molded products ( lenses for lanterns among other things ).
By 1909 the Oakland (which evolved into the Pontiac) came with a windshield as standard equipment and four years later the 1913 Chevrolet came equipped with one. Other cars had windshields but they were being offered as either a factory supplied option or as an accessory by someone with access to a supply of surplus glass.
America was booming. There was an enormous demand for store front plate glass windows huge mirrors and similar large pieces of glass. Plate glass came in whatever size the forming table happened to be and the entire plate of glass was polished before a piece the size needed for someone’s store window or back of the bar mirror was cut from it. Glass dealers and manufacturers were delighted to find a market for the remnants.
Until World War I few American cars were closed in. Some of them didn’t even have provision to put up a roof much less side curtains. But starting in about 1915 what was known as the “California Top” began to catch the motorist’s fancy. This innovation provided side curtains with celluloid windows. Originally designed to provide protection against rain and dust people quickly began to leave the side curtains up all the time to keep the wind out. At the same time techniques of body making had reached the point where it was almost as cheap to build an enclosed body as it was an open one. The deflation of 1920 reduced the price difference even further and in that year just less than one in five cars had enclosed bodies. Closed bodies meant glass rather than celluloid windows.
The demand for the fifteen or twenty square feet of glass in an open car could be met by using glass left over from other industrial purposes; the demand for the glass required by side and rear windows could not. General Motors through its Fisher Body subsidiary bought the National Plate Glass Company at Ottawa Illinois and the Saginaw Glass Company of Saginaw Michigan. Saginaw had another plant at Blairsville Penn Sylvania and altogether Fisher (which is to say General Motors) had a capacity for making 10 million square feet of glass annually.
Ford bought a lot of glass and then bought out the Allegheny Plate Glass Company of Glass-mere Pennsylvania as well as building its own plant at its enormous River Rouge facility.
The Ford facility was enormous. Molten glass came from a melting furnace in a steady stream down an incline spreading as it moved until it formed a band 40 inches wide. Then it passed through a series of rollers and annealing furnaces 440 feet long. (It took two and a half hours for the trip.) At the end of the “leer” it was cut into lengths for grinding and polishing.
All the glass now on the highways was getting to be a major problem. By 1923 half of the injuries people suffered in automobile accidents were caused by broken glass.
Safety glass had already been developed and a British patent for a sandwich of glass (glass celluloid glass) had been issued to J. C. Wood as far back as 1905. The first safety glass had been offered for sale (not only for automotive purposes but for use in store doors and so on) by the Triplex Safety Glass Company of London in 1913. It had been used in many military applications during World War I and it was obviously the thing to solve the people getting cut problem except for one thing: You couldn’t see through it after it had been in place in an auto wind shield for a while and had been subjected to heat and cold and vibration.
The celluloid in the middle either discolored or came loose or both. Water would seep into the sandwich during a rainstorm and then freeze that night and in the morning there would be a cracked windshield.
The early patents called for the celluloid to be cemented in place with Canada balsam. When that didn’t work camphor was used. There was no great breakthrough in technology until the use of vinyl plastic as a combination centerpiece and adhesive came along long after World War II but by 1929 a satisfactory product had been obtained by improvements in the interlayer and by sealing the edges of the final assembly. It was the era of the gangster and bulletproof (actually bullet resistant) glass was even produced. It was alternate layers of glass and celluloid an inch and a half thick or even thicker.
The idea of safety glass is simplicity itself. When it is broken the pieces adhere to the interlayer rather than fall off. Its widespread use however exactly doubled the area of glass required for a particular application. There were two pieces of glass required. Although each piece was half as thick as a single layer had been (and the amount of raw materials about the same) each of the layers of glass required grinding and polishing. It is just as time consuming to make a sheet of glass one eighth (or one sixteenth) inch thick as it is to make a sheet a quarter of an inch thick. Not only was the use of safety glass going to be more expensive it was going to require a doubling of the glass making capabilities of American industry. On top of that each year more and more cars were being made so the basic demand for glass was growing steadily too.
In 1930 General Motors decided to get out of the glass making business. They sold their glass factories to the newly formed Libbey Owens Ford (the Edward Ford Plate Glass Company and the Libbey Owens Sheet Glass Company had just merged) Glass Company and arranged to buy all their glass from it. Ford continued to make its own glass and to buy glass from other manufacturers as well; and other auto manufacturers simply bought glass where they could.
Everybody spent enormous sums of money in an attempt to come up with a laminated glass which would not only stay together in a sandwich despite heat cold and vibration but which would work better and cost less. A major advance came in the early 1930s when cellulose acetate was developed for the interlayer.
In 1931 20000000 square feet of glass were made for automotive use. Four years later the figure was 70000000 square feet. In 1932 the use of safety glass in school buses and public vehicles (buses and importantly taxicabs) was made mandatory by California and Michigan. By 1937 thirty states had similar laws and automobiles now came with safety glass windshields as standard equipment.
There was a cost problem. There are windows besides the windshield in cars and putting safety glass in all of them was nearly prohibitively expensive and posed design problems as well. Safety glass was heavier than plate glass and running it up and down in side windows posed problems including the basic one that since side windows couldn’t be as well insulated from vibration (because they had to move ) as windshields could they continued to separate. Tempered glass was developed starting about 1937.
Tempering is a process borrowed from metalworkers. Steel (for knives for example) is heat treated which rearranges its molecular structure. Steel by various heat treating processes can be made stiffer or more flexible or harder or softer. Glass it was learned could be treated the same way. Plate glass when given the proper heat treatment could be given very desirable characteristics. It could be made so that it would be five times as strong as un-tempered glass. That is that it would take five times as much shock as regular glass before breaking. It will also bend much further than ordinary glass before breaking and this means it can be twisted (as for example when the car body flexes) where other glass cannot.
But most important when it does break rather than breaking into large jagged shards it shatters into thousands of small pieces whose edges are rounded rather than pointed.
The ultimate step has been to make safety (that is laminated) glass using layers of tempered glass around a vinyl center. Single layer tempered safety glass is commonly used in windows other than the windshield. Not only is it cheaper and lighter than the layer safety glass but it meets ever more rigid safety requirements established by the federal and state governments. It has been suggested only half facetiously that the function of layered safety glass in the windshield is not only to keep the glass from shattering into dangerous shards when broken but to keep the car’s passenger’s inside the car in a wreck. The layer material is so strong and so elastic that it often does just that.
A really major breakthrough in glass manufacture came in June of 1958 when a British patent was issued to Pilkington Bros. Ltd. for a “float process” of making glass.
Glass comes in a molten form from the melting furnace and passes through a series of rollers which reduce it to the desired thickness while still molten. It then passes onto the surface of a huge tank filled with molten tin heated to a higher temperature (at one end of the tank) than molten glass. Molten glass is a liquid and flattens itself out. The bottom of the sheet of glass is perfectly smooth because it is floating on the perfectly smooth surface of the molten tin. The upper surface is subjected to blasts of heat from natural gas flames keeping it molten and smoothing it out by natural action. As the sheet moves along the tank of molten tin the temperature is gradually and with great precision reduced until the molten glass changes back into a rigid state. It comes out of the machine perfectly polished and ready to be cut and put to use.
Until after World War II virtually all windshields were flat; pieces of flat glass were fitted into a frame. If the windshield was angled it consisted of two pieces of flat glass in frames at angles to each other.
Then the glass industry at enormous expense learned how to mold safety glass in really intricate forms. One sheet of glass would curve around the hood curve inward as it rose to the roof line and sometimes then fold inward at the front edge of the doorframe. It was at least as much a technical accomplishment optically as it was mechanically and chemically something which can best be demonstrated rather than explained. Look through the curves of a common water glass and see how much distortion (light wave bending) there is. We look through elaborate curved windshields and there is just barely detectable distortion. Glass has of course other applications in automobiles.
Headlights are still made of glass molded glass forming lenses although most parking stop and turn signal covers are now made of plastic. Glass will probably be around for a long time in headlights which are really a form of light bulb a sealed glass vessel containing a wire which glows in a suitable gas filled atmosphere through which electricity is allowed to flow. Plastic just doesn’t seem to have the necessary physical characteristics as glass for this purpose.
Fiberglass in the form of either insulation or (as in the Corvette until recently) as the body itself can be found in about any car on the road. It is not however really a product of space age technology. The Egyptians long before Christ customarily decorated their glassware with thin threads of glass and it was a common practice to make decorations of glass threads in Germany as long ago as the waning years of the Holy Roman Empire.
By the 1700s making fiberglass was a fairly common practice. A tube of glass was heated and then pulled apart from both ends. By 1908 the technique had evolved into an industrial process. Molten glass flowing through small holes in a pipe coming off the melting pot was quickly drawn into threads as it cooled.
It was still however more of a curiosity than a practical material. Its qualities (a “wool” which won’t rot which not even the most dedicated bug wants to eat and which can be made from cheap readily available raw material is of obvious value) were well known but it could not be made in quantity at a reasonable price despite the cheapness of its raw material until 1929.
In that year three Germans F. Rosengarth and two brothers named Hager developed a technique which while not perfect opened the door to mass production of fiber glass. They poured a thin stream of molten glass onto a rapidly spinning flat plate of clay; centrifugal force sent it shooting out in all directions in fine threads. The technique wasn’t perfect: Sometimes there were beads and lumps of glass as well as fibers but it was the best method yet developed. (The same technique described as “revolutionary” was recently introduced to produce lead shot for shot shells which previously had been formed by dropping molten lead from a great height.)
There are three techniques of manufacture presently in use. “Glass wool” is made by Owens Corning and others by allowing molten glass to flow from the heating furnace through small holes in a piece of pipe. As it comes out of the tiny holes high pressure streams of air (sometimes steam) are blown against the glass stretching it and cooling it at once. This produces tiny fibers about nine inches long and 0.00035 0.00080 inch in diameter. They’re sprayed with a resin to bind them together and can then be cut into blocks and blankets and so forth.
The second process makes glass textile fibers. A trough is filled with glass in the form of marbles. The trough is heated and by the weight of the glass above the molten glass on the bottom is forced through fine holes drilled in precious metal (normally platinum). The melting tank is kept full (and the pressure on the bottom thus constant) by putting in marbles at the same rate as the fibers are withdrawn from the bottom. When the threads are formed they are fed through an eye and wound on a spool very much as wool is wound on a spool. Once on the spool the glass fibers can be woven like any other material for upholstery or whatever is wanted. Some of it is pressed into mats (with a binder) and used for plates in storage batteries for cars and other purposes. By laying a sheet of fiberglass material in a mold and then treating it with a resin binder fenders door panels or any other part of a car body can be made.
The third technique continuous fiber uses molten glass flowing through really tiny holes. The threads are gathered up and wound on a large revolving drum. A thread made of 100 fibers is only 0.00022 inch in diameter and much too fine for weaving. A number of threads each of 100 fibers are woven together and then the threads are woven into material which has a soft silky feel and enormous strength.
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