The main difference between tempered and laminated glass is in the way each is produced. Laminated glass is made by sandwiching a glass substrate (also called a laminate or polyvinyl butyral) between two additional sheets of glass, while tempered glass is made by heating and cooling a large piece of glass in rapid succession. Both types of glass are heated, and while hot, large pieces of glass are rolled onto rollers to conform to the shape that fits the pattern of the windshield. Both methods create strong, durable glass used in automotive windows and windshields, but each has its own set of characteristics and behaviors.
Laminated glass is beneficial because if it gets hit during a car accident, the windshield or window won’t shatter into a million little pieces. Instead, the windshield or window will stay together but have tons of cracks in the glass, but for the most part, the broken pieces will still stick together instead of being thrown in a hundred different directions. In the event that a stone or other object hits the windshield or window at high speed, the windshield will also not shatter, however a crack or dent could appear, obstructing the driver’s view. Fortunately, most cracks or chips can be easily fixed with the help of a professional windshield repairer or yourself using a windshield repair kit or resin.
Tempered glass is also very strong, however it can break into a million tiny pieces. The more the heating and cooling process is done in rapid succession, the stronger the glass will be, however, it will also become more brittle. Heating and cooling actually causes the glass to compress, making it 5 to 10 times stronger than it originally was. That compression is also what causes glass to break into blunt pieces instead of sharp, jagged (and dangerous) shards.
While it’s still safer than breaking huge, sharp shards of glass, you don’t want a windshield made of tempered glass. That is why tempered glass, when used in cars, is only used for the driver, passenger, and rear windows. While it may seem unsafe to use breakable glass in a car, there are two good reasons why it is done. Firstly, the use of this type of breakable glass can be useful if there has been an accident or other emergency where a rescue team needs to break the window to get someone out of the vehicle. The other reason is that using tempered glass is much cheaper than using laminated glass.
Although it is more expensive, the use of laminated glass offers many additional benefits in addition to its resistance to breaking. Laminated glass, due to its glass substrate and two layers of glass, is actually a buffer against loud noise and UV rays from the sun. This is another reason why it is used for the windshield, as it is the largest window in a vehicle. This is the same reason why laminated glass is often used for windows in high-rise buildings that receive a lot of direct sunlight. Some car manufacturers have even been contemplating the use of laminated glass as a vehicle roof. Many concept cars feature this idea, which is called a sky roof.
Understanding the differences between laminated and tempered glass should help you see why each type can be used. Today, the windshields of all cars are made of laminated glass, while tempered glass is almost always used for rear-view and side mirrors. However, some car manufacturers now use laminated glass in the rear passenger windows. If you are concerned that these windows cannot be easily broken in an emergency, it is important to find out what type of glass is used in the car you are considering buying.