“Why does the train have the little dots by the window? What do the black dots on train windows do? Technically called “frits,” the little dots are a “baked-on... pattern that’s there because the glass and the metal frame around it expands at different rates.” Though the poster describes the dots as “ceramic,” Autoglaze explained they’re actually painted black enamel, a ceramic coating. Are there any other benefits to black dots on windscreens and windows?