You may have noticed a lot of car windshields have these random black dots along the top edges. I always assumed these were just sad cases of car pimpin’ gone wrong, like the kind of shit even Xzibit wouldn’t condone, but guess what? They serve a purpose, and it’s a pretty nifty little purpose at that.
So cars have a black band of ceramic paint called a ‘frit’ along the edge of a windshield that helps the windshield stay in place. It also helps sealant adhesive stick to the glass.
When the windshield is being made, the glass is heated and bent in an industrial oven, and the frit heats up and expands.
This creates an optical distortion in the glass, also known as ‘lensing’. The black dots help spread the sharp thermal gradient between optical glass and frit to minimize and to help mask the distortion. In layman’s terms, it helps keep things together when the glass expands from the heat and protects the glue from UV light and ageing.
Apart from this, it also serves an aesthetic purpose, helping to cover up the glue on the edge of the windshield.
Damn son! Those little dots do a lot of work!