During the early 20th century, horseless carriages started using glass to protect drivers from harsh winds. However, the standard form of glass used in those times didn't adequately protect occupants from flying debris. It also posed a risk to the occupants if an object struck the glass or if the vehicle was involved in an accident.
In 1903, French chemist Edouard Benedictus stumbled upon the secret to shatter-resistant glass when he dropped a glass flask filled with a dried collodion film. He found that the glass coated with the film cracked, but kept its original shape. However, this laminated glass wouldn't be implemented in automobiles until the 1920s [source: Time].
Automakers used laminated glass in their windshields to optimize occupant safety during accidents and to protect passengers from projectiles during normal driving conditions. For all its benefits, though, the first types of laminated glass offered limited puncture resistance. Today's laminated glass consists of a thin layer of polyvinyl butyral (PVB) inserted between two layers of solid glass.
In addition to laminated glass, automakers began to use tempered glass in the late 1930s. This type of glass is used in the vehicle's side and back windows and gains its strength through a heating and rapid cooling process that strengthens the glass' outer surface as well as its core.
By the 1960s, the American public had become increasingly aware that automobiles needed to be designed for more than just looks. This realization derived partly from consumer crusader Ralph Nader's work to expose the dangers posed by certain vehicles and the need for government safety standards. In response, the U.S. government formed the National Highway Traffic Safety Administration (NHTSA) in 1970 [source: Bowen].
Since then, NHTSA has implemented regulations affecting all areas of vehicle safety, including automotive glass. Some of the Federal Motor Vehicle Safety Standards (FMVSS) for automotive glass include:
- FMVSS 205 -- This set clear standards for automotive window transparency and the strength of automotive glass required to keep occupants inside the vehicle during accidents.
- FMVSS 212 --This windshield mounting standard was established to ensure a certain level of windshield retention strength during accidents.
- FMVSS 216 -- This legislation implemented a standard for roof rigidity in case of a rollover.
- FMVSS 219 -- This standard states that no part of most passenger vehicles can penetrate the windshield more than 6 millimeters (0.24 inches) in a crash.
Now that we know how automotive glass came to be, let's find out how it's made.