You probably see them every day when you drive to work: those black little dots around your windscreen. They are intriguing because they seem to be present in almost all cars today, but these black dots seem to be so underrated that no one even bothers to ask why they’re even there in the first place…
What 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 windscreens and other parts of your car’s glass windows. And believe it or not, they actually serve four main purposes:
- 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.
- They help preserve the urethane sealant used to bond the glass to the frame. They use the 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.
- 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 windscreen’s glass, creating an optical distortion that makes either straight lines look curved or bowed inwards toward the centre. Those “gradually sinking” black dots help lessen this phenomenon by dissipating the heat and spreading it out evenly.
- 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 on the eyes.
Frits are slowly evolving over the years and modern cars now add “third visor frits” right behind the rear-view mirror to block the sun between two sun visors.
So there you have it, those black little dots have a purpose after all!