The black dots on windshields and windows and the black rims
that surround them, are more than decoration.
From the 1950s and
1960s onward, car manufacturers began using an adhesive to hold
car windows in place, rather than metal trim.
The black rims around
car windows are called “frits.” The frits and the dots that
border them are made from ceramic paint. The frits are there to
hide the adhesive. These painted rims are baked into the window
and hold the glue in place, which in turn holds the windows in
place.
The dots are there to
make an aesthetically pleasing transition from the thick black
lines to the transparency of the window. They are positioned in
a halftone pattern, getting smaller and farther apart as the
black recedes. This pattern is less jarring to the eye than
opaque black paint juxtaposed with transparent glass.
Their other purpose is
to provide temperature control. To get the glass of windows and
windshields to be bent the way it is, the glass is heated up.
The black-painted glass heats up faster than the rest of the
window. The dots distribute the heat a bit more even and prevent
the windshield from warping in the heat.