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Info from PPG
1940 Parts Catalog
(click to enlarge)
PPG
Labels
& Trademarks
for Automotive Laminated
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SAFETY
PLATE GLASS
The highest quality of Safety glass for automobiles. Only in Safety Plate Glass is it
possible to obtain complete freedom from distortion together with protection from the hazards of flying glass. For this reason, many states require replacements of Safety Plate Glass in windshields, not just Safety Glass.
Safety Plate Glass is approximately 1/4" in thickness and is composed of two pieces of clear Polished Plate Glass,
approximately 1/8" in thickness, and a sheet of flexible plastic material. The inner surface of the plate glass is coated with a transparent cement and the three units are bonded or laminated together, under heat and pressure, with the plastic
in the center. Broken pieces thus tend to stick to the center sheet of plastic,
when the outer surface of plate glass is shattered by a heavy impact.
Safety Plate Glass is standard factory equipment for most makes of automobiles.
BENT TEMPERED GLASS
This type of glass is between four and five times as strong as the Plate Glass from which it is fabricated. Its strength is derived from the fact that its surfaces are under high compression, induced
through rapid heating followed by instant cooling. When the limit of its mechanical strength
is reached, Bent Tempered Plate Glass will disrupt into small granule
fragments. These particles tend to interlock and to remain in the same plane of the glass.
SAFETY SHEET GLASS
The process of lamination is identical with that
used in the manufacture of Safety Plate Glass. Safety Sheet Glass is
made by laminating one piece of single strength or window glass and
one piece of double strength sheet or window glass to an interposed sheet
of transparent plastic material. Safety Sheet Glass offers the same
protection and approximately the same thickness as Safety Plate
Glass, yet it does not have the same perfect, undistorted vision.
GENUINE POLISHED PLATE
This type of glass is universally recognized as the only glass giving an absolutely true vision. Both sides of the glass are ground until both planes are absolutely parallel, and the process is completed by polishing until a high
luster is obtained, entirely eliminating any distortion to an article
viewed at any angle.
Windshields should, without exception, be of Plate Glass, either Safety or in single thickness, to provide perfect vision, free of any distortion, for the driver of the car. Use of Genuine Polished Plate Glass will also
eliminate possible chance of eye strain due to long drives behind wavy glass.
HEAVY SHEET GLASS
Modern methods of manufacturing Heavy Sheet Glass make possible a brilliance of
finish, uniformity of quality and thickness, and a flatness of surface, hitherto considered unattainable in sheet glass.
This type of glass costs less than plate glass, though it is comparable in strength, thickness and
luster. However, if viewed at an angle there is a distortion perceptible.
Heavy Sheet Glass is in frequent demand due to its economy, and is especially suitable for doors and windows in low-priced or used cars.
We advise against its use, however, in windshields, as here true vision is an absolute requisite for safety and protection
against eye strain.
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