Auto Glass Explained
At Instant Windscreens we always talk about auto glass rather than just glass. This is because all the glass used in vehicles is different to regular glass, and specifically designed for vehicles of all types. Even in normal use–driving around town rather than driving on a dirt road–the glass in your vehicle is exposed to much harsher treatment than the windows in your home, so they need to be a lot tougher. But some glass, such as that used for windscreens, serves more than one purpose. Which is why it is always important to have any damage repaired as quickly as possible. So, how is auto glass different to other glass?
Tempered Auto Glass
The side and rear windows of your car–sometimes referred to as sidelites and backlite–use tempered auto glass. Tempered glass is made by heating glass and then rapidly cooling it to room temperature. This gives the glass both compressive and tensile strength, resulting in glass that is stronger than regular glass panes, but not unbreakable. The glass is tough enough to withstand impacts from many types of flying debris, but not so tough that it can’t be smashed in an emergency. But one of the most important aspects of tempered glass is that when it does break, it shatters into smaller pieces that are less likely to cause serious harm.
Laminated Auto Glass
Typically reserved for windscreens, laminated auto glass consists of two layers of glass that are fused together with a layer of special resin film between the two layers of glass. The glass is made using a similar process of heating and rapid cooling used on tempered auto glass, and it would also be moulded into the curved shape of windscreens. Once the layer of film is added, the two layers of glass are then put through an additional process of heating and pressure, causing the two layers to bond and fuse with the resin film. Each layer of glass is usually around 2.5mm thick, with the film layer less than half a millimetre thick. As with tempered glass, the glass is slightly tougher than other glass, helping it withstand most types of impacts when driving. The difference between laminated and tempered auto glass is that with more severe impacts the glass does not shatter, thanks to the film layer bonding the two layers of glass to each other. The glass will crack, but the film ensures it doesn’t break completely. This doesn’t only keep occupants safe from flying glass, it also adds structural strength to the vehicle in an accident. The toughness of laminated auto glass help ensure that the airbags deploy properly, occupants are less likely to be ejected from the vehicle, and also keep the roof of the vehicle from collapsing in the event of an accident.
Laminated auto glass is not impervious to cracks and chips, but because of the lamination process, many of these can be repaired without replacing the windscreen. However, it is always advisable to have repairs done by qualified auto glass technicians who are able to check that the crack or chip hasn’t penetrated the first layer of glass all the way to the laminate. When this happens it increases the risk of the glass separating from the laminate, making the glass weaker and less likely to withstand a heavy impact without breaking instead of cracking.