Why Are There Tiny Black Dots Around the Edges of a Windshield?

May 21, 2024


You’ve may have noticed a black band and tiny black dots around your windshield (or windscreen for those in the UK). These dots and the band are present on almost all cars today, but why are they there, and what purpose do they serve?

The black band and black dots have a technical name; they’re called a frit. A frit is essentially black enamel baked around the edges of a windshield during the manufacturing process. They start as black bands near the edges and gradually transform into smaller and smaller black dots as they move inward. The black band and dots can also be found on other car windows.

The black band and dots serve a multitude of functions. One key role is to enhance the adhesive’s grip on the glass by creating a contact point between the car’s frame and the glass. The black enamel of the frit also plays a crucial role in blocking the sun’s harmful UV rays, thereby protecting the urethane sealant underneath from melting or breaking down. This ensures the windshield remains securely in place.

The black dots also help with temperature distribution. When the solid black band or frit band heats up faster than the windshield, it creates an optical distortion in the glass, causing straight lines to look curved. The change in the dot size allows the heat to be dissipated and spread out, decreasing this optical distortion.

The frit is not just a functional element, but also adds to the aesthetic appeal of the car. They make the windshield more pleasing to the eye when viewed from the outside. Without the dark band and dots, the squished adhesive used to affix the glass to the car’s frame would show through. The gradually decreasing size of the dots also allows a fading effect, which is more aesthetically pleasing when viewing the car.

You can also find a frit behind the rearview mirror in modern cars in different configurations. This is known as a “third visor frit.” Its purpose is to block the sun between the two visors.

rearview mirror
A Third Visor Frit

Sources: Autoglaze UK , The Drive, Travel and Leisure

About the author 

Daniel Ganninger - The writer, editor, and chief lackey of Knowledge Stew, the author of the Knowledge Stew line of trivia books, and editor of Fact World and the Knowledge Stew sister site on Medium, our ad-free subscription sites. I hope you learn many new things here that add to your knowledge.

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