If you spend a lot of time staring straight ahead while stuck in traffic, you may have wondered what those tiny black dots circling the edges of your car’s windshield are. Or maybe you've never even noticed them. They’re easy to miss, but according to Jalopnik, they serve a few important functions.
That black strip that wraps around the window is called a frit or a frit band, and it’s essentially ceramic paint that has been baked into the glass in a way that makes it impossible to scrape off. It’s there to protect the urethane sealant holding your windshield in place from ultraviolet rays, which, under less secure circumstances, could cause the glass to pop out.
“The frit band also acts to provide a rougher surface for that adhesive to stick to, and it’s a visual barrier, preventing people from seeing that nasty glue from outside,” David Tracy wrote for Jalopnik. The frit has been commonplace since the 1950s and ‘60s, when car manufacturers started swapping out metal trim for adhesives.
Ok, so that explains the solid black strip, but what about those dots?
The reason the dots get smaller as they move inwards is because it creates a gradient pattern that’s more aesthetically pleasing and less obvious—and distracting—to both drivers and passengers.
The dots aren’t there just to look pretty, though. Much of the design has to do with the way windshields are made: When the glass is bent in an oven, the frit heats up faster than the rest of the windshield because it’s black. To reduce optical distortion as a result of this thermal disparity, a dot gradient is used to even out the temperature.
You can also thank a second set of dots on your windshield—right behind the rearview mirror—for helping to keep the sun out of your eyes as you drive.
Now that you're an expert on frit bands, check out our guide to the meanings behind 15 different symbols on your car's dashboard. Never again will you miss another tire pressure warning.