“Autoglass” is a contraction of “automobile glass”. The origins of this latter expression are interesting. “Auto” is derived from the Greek word “auros” meaning “self”; “mobile” is derived from the Latin word “mobilis” meaning “movable”. “Glass” comes from the Anglo-Saxon “glaes” which came from the German “glas”. Hence “automobile glass” means the glass parts of a vehicle which carries its own self-propelling mechanism.
In modern times the term “automobile” has been reserved to refer to a “car” for passengers. Many people use the word “auto” as a synonym for “car”, because they are not familiar with Greek. AutoGlass means literally “self-glass”. However, when we say “autoglass” we are referring to the substance in the windscreen, windows and panels in the upper parts of the four sides of a car.
The glass surrounds the occupants. Some cars have a glass panel above the occupants- This panel can also be included under the heading “autoglass”.Autoglass in electric cars will, one day, also refer to adjustable panels of glass attached to, and sited above, the roof of the car. These panels will consist of glass sheets, on the inside surfaces of which has been deposited a thin layer of the photo-voltaic metals copper, indium and gallium together with a selenide.
When the weather is clear these panels, exposed to daylight, will produce the electrical energy needed to power up the car’s batteries. Any brand of photo-voltaic autoglass panels in future solar powered electric cars will, of course be readily obtainable from West Rand Auto Glass. There are many varieties of present day autoglass. However, only a few kinds are used in ordinary automobiles. Any piece of autoglass must have a uniform thickness, no matter what its variety. Sheets of glass of constant thickness are manufactured by the float-glass process.
The process was the brain-child of the British glassmaker Alastair Pilkington. Around the year 1950 Pilkington happened to see melted grease solidifying on the surface of his wife’s washing-up water. He noticed that the layer of solidified grease had a perfectly smooth surface. He wondered whether sheets of glass made in a similar way would also be smooth. After spending millions of pounds in experimentation, Pilkington found in 1952 that melted tin had a surface on which melted glass could be floated to form glass sheets of constant thickness. Such sheets had perfectly smooth surfaces (They could also be manufactured in various tints. Tinting was first achieved in 1967.) Sheets of float-glass can easily be laminated to form an autoglass, if they are perfectly flat. That is, a transparent plastic named polyvinyl butyric can easily be sealed between two sheets of heated float-glass.
However, windscreens of modern cars are curved. To produce curved laminated autoglass windscreens, complex methods and exact conditions are required which will not be described here. The capital costs of setting up a windscreen manufacturing plant and of training experts to operate such a plant are among the reasons for the high prices paid for windscreen replacements nowadays. The principle brand of laminated glass sold in Gauteng and obtained from West Rand Auto Glass has the trade name shatterproof.
All American cars must, by American law, be fitted with front windscreens made of laminated autoglass. Most British cars had front windscreens which were not laminated. Instead of being laminated, British windscreens were usually manufactured using a very tough autoglass. Float-glass sheets are changed into tough autoglass by a process which makes the glass about six times stronger than the glass of the individual sheets in laminated autoglass. The sheets of float-glass are heated to just below the softening temperature. Both surfaces of each sheet are then rapidly cooled with jets of cold air or of other gas. The surface layers tighten over the inner layers which cannot shrink and as they in turn cool down. The surface layers are tightened even further.
Autoglass formed in this way can be broken only by concentrated great force. When it does break, the tension in the inner layers causes the entire sheet to disintegrate into pieces with smooth sides of area less than one square centimeter each. These pieces have concave (i.e. inward curving) cross sections because of the now permitted contraction of the inner glass layers. Toughened autoglass sold in Gauteng can be obtained from
West Rand Auto Glass. Both laminated and toughened autoglass windscreens, windows and panels were, in the interest of occupant safety, designed to absorb the energy of impacts in a controlled manner. For this reason both kinds of autoglass are often termed “safety-glass”. Their respective advantages and disadvantages are described in other articles of the West Rand Auto Glass website.