Useless fact
What are the black dots on car windshields called?
The black ceramic band and dot pattern found along the edges of a car's windshield are called the frit.
The black band and surrounding dots on car windshields, known as the frit, are made of baked-on ceramic paint that cannot be scraped off. This feature was introduced by automotive manufacturers in the 1950s and 1960s as car makers transitioned from using metal trim to adhesives for holding windshields in place. The frit serves several crucial engineering purposes. Its primary function is to provide a rough surface that allows the polyurethane adhesive to bond securely to the glass, while also shielding the adhesive from ultraviolet rays that would otherwise degrade it over time. The transition from a solid black band to a gradient of tiny dots is not just decorative; it helps distribute thermal stress. Since the black paint heats up much faster in the sun than the clear glass, the dot pattern mitigates the temperature difference, preventing the windshield from cracking due to uneven thermal expansion.
Why this is true — The term 'frit' is the standard industry name for the baked-in ceramic paint on automotive glass.