You probably see them every day when you drive to work: those black little dots on your windshield. They are intriguing because they seem to be present in almost all cars today. There are some variations, of course. The most popular ones you see often have round shapes, while others have more of an angular form. But regardless of what they look like, these intriguing black dots seem to be so underrated that no one even bothers to ask why they’re even there in the first place.
And so now we’re asking ourselves the same question: What the heck are they?
These dots are actually called frits.
A frit is a painted black enamel that’s baked around the borders of a windscreen during the manufacturing process.
They often start out as solid black bands near the edge, and gradually dissolve into small dots at the outer edge.
They are seen on windshields and other parts of your car’s glass windows. And believe it or not, they actually serve four main purposes:
First, they serve as a contact point between the glass and car frame. They create “etches” on the surface, making them rougher so the adhesive can stick better to the glass.
Second, they help preserve the urethane sealant used to bond the glass to the frame. They use those black enamel outside the windshield to block the sun’s ultraviolet rays from melting the adhesive underneath the band. This keeps the windows firmly glued in their place.
Third, the black dots, or “dot matrix” actually help distribute temperature evenly to lessen optical distortion or “lensing”. This happens when the frit band (the solid black one) heats up much faster than the windshield’s glass, creating an optical distortion that makes either straight lines look curved or bowed inwards toward the center. Those “gradually sinking” black dots help lessen this phenomenon by dissipating the heat and spreading it out evenly.
Fourth, frits are also there for aesthetic purposes. If you look closely, the contrast between the dark band and the transparent glass can look too obvious even when viewed from afar. Creating a halftone pattern or “dot-matrix” allows a gradual decrease in size, making the transition much more subtle and easier to the eyes.
Frits are slowly evolving over the years. Modern cars now add “third visor frits” right behind the rear view mirror to block the sun between two sun visors like this one:
Some car manufacturers have also become more creative by using their brand logos as substitute for these small dots. Others add graphic images to make them more unique and eye-catching such as this one:
So there you have it. Obviously, this information won’t end world hunger or fight terrorism, but at least now we can rest in peace knowing that those black little dots have a purpose after all.