Those black dots on car windshields and windows are something I’ve noticed, but I’ve never really thought about them. They’re just one of those things that exist in the background of my life, seemingly purposeless.
Except it turns out they actually do have a purpose.
I think we can all agree that windshields are important. Back in the day, windshields used to be held in place by metal frames. These days, windshields are held in place by adhesive. Obviously, it’s a really tough adhesive, but it still needs something to grip. That’s where the frit comes in.
The black band running around the edge of windows is called a frit. The frit is a band of ceramic paint that provides a better surface for the adhesive to stick to.
That’s not the only reason for the frit, though. The frit also keeps UV rays from deteriorating the adhesive, ensuring that your windshield stays put.
That explains the black band, but what about those dots? Well, the dots actually do a few things. First, they provide a bit of shade, which is why there are extra dots behind your rear-view mirror. Second, they’re aesthetic. Glass manufacturers thought that the black dots would look a bit less jarring than just a plain black band.
Third and perhaps most importantly, the dots help with the baking process. The black band heats faster than the clear glass, which could cause warping. The dots prevent that warping so your windshield stays clear.
Who knew those little black dots were so useful?
Oh, and those lines on your rear window? They’re for your rear defroster. They help spread the heat evenly.