How They’re Made: Windshields

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 made from a variety of materials. From high-performance speedsters to orbiting rockets, each windshield has a unique design. But how exactly is the average, everyday windshield made?

It all begins with a simple sheet of clear glass. The correct shape is scoured into the glass. A hot torch then travels over the scour marks and the windshield breaks free. This scouring and torching technique allows for a clean cut.

However, the edges still need smoothing.

The glass edge is sanded and polished in a process called ‘seaming’. Afterward, the glass is washed with soapy water and moved on to the next station.

Each sheet of glass is sprayed with a nonstick substance (usually talcum powder and water) to prevent sheets from sticking to one another. Two identical glass sheets are then stacked together. This arrangement is temporary, as a third layer of vinal must be placed between the two sheets.

Down the line, a black outline is silkscreened onto the windshield.

This thick, nontransparent border is mostly used to hide any unsightly aspects surrounding your car’s windshield. It is merely a cosmetic feature.

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.

Resting atop the iron, the glass is placed into an oven called a bending leer at 1382 degrees Fahrenheit. While heating, the glass sinks into the correct bend. Once complete, the glass is slowly cooled. This hardens and strengthens the windshield.

Once cooled, the lamination process can begin.

A sheet of vinyl, cut in the shape of the windshield, is sandwiched between two identical sheets of glass. At this stage, the glass is nontranslucent. The vinyl still needs further processing.

The windshield is now sent through a nipper.

This machine sends the windshield between rollers to remove air pockets from the vinyl. At this stage, the brackets for the rearview mirror are firmly attached. From here, the windshield is placed in an autoclave for roughly an hour. An autoclave is essentially a large pressure cooker.

When the autoclave is finished, the windshields are removed to reveal a clear sheet of laminated glass. Although the glass is ready for wholesale, a series of inspections and tests must be performed.

One test 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 the height at which it falls equal 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 reviewed under polarized lights to reveal stress defects. Trained eyes carefully examine each windshield for stress marks. If any are found, the windshield is removed and recycled. After a final inspection, the windshield is ready to be shipped and sold to various automakers and glass shops around the world.