Back when cars were referred to as “horseless carriages,” manufacturers already saw the need to protect passengers from the harsh winds and the other elements that come with driving these vehicles at a certain speed. So they put up windshields made of standard plate glass.
The problem with having ordinary window glass for windshields, however, is that it puts drivers and passengers alike at risk of serious injuries, particularly if they figure in an accident. In case of an impact, a standard plate glass windshield will break into pieces sharp enough to cause injuries and deaths.
Thankfully, by the late 1930s, cars already carried safety glass, which is manufactured using processes designed to reduce not only its likelihood of breaking but also of its causing harm in the event of a crash.
Today, safety glass is standard for all automobiles, and there are two types of auto glass that carmakers typically put in their vehicles: laminated and tempered glass.
Take two sheets of glass, stick them together using a layer of resin called PVB (polyvinyl butyral) right in between, and fuse the whole glass “sandwich” using high temperatures, and you’ll have laminated glass, which holds up to impact quite well, making it perfect for front windshields.
In the event of a crash, the laminated glass of your windshield will not shatter, as it is designed to do so. The impact may break it, but thanks to the PVB layer, the glass will remain intact. There will be no glass flying around to hurt passengers. Even when the car gets involved in a head-on collision, the laminated glass will act as a cushion in case a passenger gets slammed into the window.
Aside from windshields, laminated glass is also used for shop windows, skylights, glass roofs and floors, aquariums, or any application where the likelihood of impact is high.
Also referred to as toughened glass, tempered glass is about four times stronger than ordinary glass. It is created through a process that involves heating single-ply glass to a temperature of over 600 degrees Celsius, then making it go through a rapid, high-pressure cooling procedure known as “quenching.”
Aside from being incredibly strong, tempered glass is just as safe as laminated glass, but in a rather different way. While laminated glass typically remains intact after impact, tempered glass shatters when hit hard enough by something, but not into deadly, jagged shards, but into thousands of small, dull-edged pieces reminiscent of pebbles.
There may be car models that use laminated glass for side windows and rear windshields, but tempered glass is more commonly used for them.
The same goes for sunroofs, although some models use laminated glass as well. Unfortunately, complaints of shattering sunroofs in many car models have been mounting steadily. Currently, there is still no definitive cause for such explosions. Some say external factors like debris hitting the glass at speed are to blame, while others point to the quality of auto glass carmakers use for their sunroofs. Hopefully, automakers would address this issue as soon as possible to ensure everyone’s safety.
Differences between laminated and tempered glass
There are several differences between laminated and tempered glass, aside from the ones already mentioned above.
Laminated glass is strong, but it’s not as strong as tempered glass. In fact, laminated glass will tend to crack more easily than tempered glass, which has a much higher load and breakage resistance. However, a cracked laminated glass can still be repaired, while tempered glass has to be replaced entirely, as it breaks completely when a strong enough impact hits it.
Laminated glass is also great at blocking ultraviolet light, as it blocks nearly 99 percent of UV rays, which is much higher than the 60–70% that tempered glass is capable of blocking.
There’s also a difference in cost between the two, as laminated glass is generally three to four times more expensive than tempered glass.
When it comes to windshields, you don’t have a choice, since the law requires automakers to use laminated glass. And while side and rear windows are usually tempered glass, some car manufacturers are now starting to use laminated glass for them.
Whatever differences both types of auto glass may have, you can be sure that they’ll provide nothing but the best in safety for you and your passengers.
Adrian Bell is the Content Marketing Strategist for Reliable Glass, a local, family-owned and operated business that serves the Valley of the Sun with home, commercial and auto glass repair since 2001. In his spare time, he draws and plays a game of hoops with his friends. Reach out to him on Twitter or LinkedIn.
Editor’s Note: The opinions expressed in this article are those of the author.