The history of that massive piece of glass stuck at the front of your car, van or truck actually goes way back to the earlier 20th century, when makers of horseless carriages began to put sheets of glass in front of the vehicles to protect the driver from the cold winds. However, these did not offer adequate protection against incoming debris. This glass, while useful was also not thoroughly thought through at the time and could pose a threat to the driver if the vehicle was involved in an accident.

In 1903, a breakthrough was made in the field of glass lamination; a chemist by the name of Edouard Bennedictus accidentally dropped a glass flask filled with dried up colodion film in it, he noticed  that while the glass did break, it did not shatter and kept its original shape. This led to the development of laminated glass for automobile, but the technique was not mass implemented until the 1920s. The laminated glass proved to be very effective in protecting the riders from damage that could be caused by debris or projectiles. While it was a great leap forward, this kind of laminated glass offered only marginal protection to the riders. Further research was conducted and it was found that if a thin layer of PVB (Poly Vinyl Butyral) was sandwiched between two glasses, it enhanced the glass’s strength and added a measure of resilience to it.

The glass and the PVB are sealed together by a series of pressure rollers and are then heated to ensure that the two different components bond both chemically as well as mechanically. The mechanical bond is primarily due to the “stickyness” of the PVB while the chemical bonding occurs due to the hydrogen bonding of the PVB to the glass.

The inserted layer of PVB between the glass allows the windshield to absorb the energy during an impact and gives the glass resilience against flying projectiles. A secondary advantage of having PVB is that it also deflects 95% of the UV rays from the sun. The PVB enhanced laminated glass helps with two different functions, firstly it allows the passenger side air bag to deploy properly. While the driver side air bag deploys straight from the steering wheel, the passenger side’s air bag is supposed to bounce of the windshield towards the person. The windshield has to be strong enough to absorb the weight of the passenger in the event of an accident and prevent him/her from being ejected outside. Secondly, the windshield also supports the weight of the roof of the vehicle and stops it from collapsing should the vehicle tip over.

Clearly the windshield of your vehicle is an impressive piece of technology and goes a long way to making your drive a safe one, so treat it with the same respect that you would any other part!