Flat sheets of glass were heated as they moved on a conveyor belt and the glass was allowed to sag into shaped over molds. Curved automobile glass is still manufactured by this method today. Safety glass windshields have been used for decades by the manufacturers. These windshields have a tough plastic sheet bonded between two layers of glass. The plastic layer holds the glass together in an accident and makes it difficult for an object to be thrown through the windshield.
Heated windshields are available as an option on a few luxury automobiles.
The glass is heated to quickly melt ice and snow by passing an electric current through a conductive sheet bonded between the windshield layers. The thin layer of gold may give the windshield a slight pink or copper tint but clarity is as good as with other windshields. When the heated windshield is turned on, a safety module measures the resistance of the windshield grid and turns off the power if there are any cracks that could cause electricity to pass to the outside of the glass. Heated windshields may use close to 100 volts to heat the glass and a cracked and wet windshield could give a person a nasty shock if the built-in safety module was bypassed. This type of dash display projects information such as vehicle speed, signal lights, and warning lights onto a special area of the windshield.