Ever wonder about this?

Perri Ormont Blumberg
October 15, 2018

Life has many mysteries: What is the white stuff on cooked salmon? Why does the space bar make so much more noise than the other computer keys? Is it really illegal to remove one of those mattress tags?

Well, now it's time to solve another one of such quandaries: What are those little black dots on the edges of car windshields? As automobile site Jalopnik explains, there's method behind the (seemingly random) madness. "The 'dot-matrix' you see on windows is a halftone pattern, serving an aesthetic purpose. The pattern simulates a smooth gradient by gradually decreasing the size of the solid black dots as it moves inwards. This provides a more visually pleasing transition from the black frit band to the transparent glass," writes David Tracy. The frit is a black band made of enamel that is situated on the edges of the windshield glass, cradlining the black dots you see.

As Tracy later updated the post, there's another reason that your car windshield has these black dots. "Windshields are bent in a hot oven (like the one seen here), and that, because the frit band is black, it tends to heat up faster than the transparent glass," writes Tracy, who was clued into this from an engineer with Pittsburgh Glass Works. "A sharp thermal gradient between the frit and the clear glass can cause optical distortion, or 'lensing,' so faded dots are used to help create a more even temperature distribution, minimizing this distortion (and also hiding it from view)."

Even more intriguingly, these dots also appear on the windshield right behind the rear-view mirror. In this position, they serve the purpose of shielding the sun that reflects from between the two front sun-visors, which can then hit your field of vision. This smattering of dots is known as the "third visor frit."

Here's to hoping "frit" is an answer on our next trivia night.