The History of Automotive Safety Glass
That’s not just any glass in the windshield and windows of your automobile. That’s safety glass! The safety glass used in vehicles comes in primarily two kinds- laminated and tempered.
Is this special glass a recent invention, or does it stretch back over the years? When was safety glass first used in cars?
Safety Glass’s First Use
Laminated safety glass was first used in automobiles in the 1920s. Before that, standard glass had been used, even in horse-drawn carriages, but was very dangerous in the event of a crash. Tempered glass began to take over for the side and rear windows starting in the 1930s because it was cheaper than laminated.
What is laminated and tempered glass?
The laminated glass originally used was stronger than normal glass but could still be punctured. Today’s is more advanced. It consists of two layers of solid glass with a thin layer of polyvinyl butyral (PVB) in between.
Laminated glass is known for providing high sound insulation, blocking 99% of UV rays, and flexing before shattering. For these reasons it’s used to make windshields, as well as in other situations where there is severe risk of high winds. However, laminated glass is not as strong as tempered glass.
Tempered glass is glass that is increased in strength through a heating and rapid cooling process. This endeavor strengthens both the glass core and outer surface.
Safety Glass Regulations
Since the NHTSA was formed in 1970, they have implemented regulations regarding required standards of automotive glass. These regulations include:
- Strength required to keep occupants from being ejected
- Strength required to maximize windshield retention during accidents
- That no part of most passenger vehicles can penetrate the windshield more than 6 millimeters in a crash
Due to its special properties, laminated glass is required to be used in windshields. Even though it’s more expensive than tempered, more automakers are starting to use it for side and rear windows as well.
When (and how) was safety glass invented?
French chemist Edouard Benedictus inadvertently invented laminated glass in 1903, when he dropped a test-tube containing a certain chemical and noted that the test tube cracked but did not shatter, and retained its form. Tempered glass, on the other hand, has been around for centuries.
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