The modern windshield has been around since the early 20th century. They provide an enclosed environment in any vehicle while allowing the driver to see where he or she is going. Windshields are produced in a variety of materials and used for numerous different vehicles from high performance speedsters to orbiting rockets. But how exactly is the average, everyday windshield made?
It all begins with a simple sheet of clear glass. The glass is scoured into the correct shape of windshield depending on the vehicle it will adhere to. A hot torch then travels over the scour marks and the shape breaks out of the glass sheet. This scouring and torching technique enables the cut to be as clean and unjagged as possible. Despite such a method though, the edges still must then be smoothed by a sanding and polishing process known as seaming. Afterwards the glass is then washed with soapy water and moved on to the next station.
Each sheet of glass is sprayed by a nonstick substance (usually talcum powder and water) to prevent the sheet from sticking to another sheet of glass. After being sprayed, a second identical sheet of glass is placed on top of the first sheet. This arrangement is temporary as a third layer must later be placed between the two sheets. Down the line, a black outline is silk screened onto the windshield. This thick and nontransparent boarder is mostly used to hide any unsightly aspects surrounding your car’s windshield. It’s merely car cosmetics. Following silk screening each windshield is placed under a quick visual inspection for any cracks, scratches, or screening imperfections.
From inspections, the windshield is placed on a bending iron. The glass on the iron is then placed into an oven called a bending leer at 1382 degrees Fahrenheit. Whilst heating, the glass sinks into the correct degree of bend. Once the glass is in the correct shape, it is placed through a slow cooling process to harden and strengthen the windshield. When the glass is fully cooled, the lamination process can begin.
A sheet of vinyl, cut in the shape of the windshield, is placed on top of the first sheet of glass and another, identical sheet of glass is placed on top of that. At this stage nothing can been seen through the glass as the vinyl still needs further processing to become clear. The windshield is now sent through a machine called a nipper. This machine sends the windshield between rollers to squeeze air pockets out of the vinyl to make it more transparent. At this stage, the brackets for the rearview mirror are firmly attached. From here, the windshield is placed in an autoclave for about an hour. An autoclave is somewhat like a large pressure cooker. When the autoclave is finished, the windshields are removed to reveal a now clear sheet of laminated glass. Although the glass is technically ready for wholesale, a series of inspections and tests must be performed.
One of the main tests is called the Steel Ball or Crash Test. During this test, a steel ball is dropped on the glass from various heights. The ball is meant to represent a passenger’s head and height at which it falls equal the different levels of impact. If the ball does not break through the glass, the windshield receives a pass and all others in the batch may continue on. Finally, the glass is viewed under polarized lights which reveal any stress defects. Trained eyes carefully view each windshield for stress marks and any found are removed. Once passing this final test, a windshield is ready to be shipped and sold to various auto makers and glass shops around the country.