Seeing dots on windshields
Q: Several years ago, black dots started appearing on new vehicle windshields. The dots are usually only around the periphery
of the windshield. What purpose do these dots serve? --Brad, Midland, Texas
A: Windshield glass contains a black enamel band (called the frit) around the periphery that is baked into the
glass. This black band includes a border of dots. See figure. The band has an etched surface to enable
adhesive to bond to the glass, says a sales manager at Able Auto Glass. When car manufacturers install the
windshield, they bond the windshield to the vehicle with adhesive placed on the etched part of the black
enamel glass area (inside surface). The outside of the enamel band shades the adhesive from the Sun and
protects it from ultraviolet radiation. The band also serves a cosmetic purpose by covering up the adhesive and
gives the windshield edge "a more finished look."
[Steve Coyle, Auto Glass Specialists] The black dots blend the border into the glass
Rather than a straight black edge, the dot border blends the solid band into the clear glass, says Steve Coyle at Auto Glass Specialists.
Some windshields also use the dots as a third sun visor to block the Sun behind the rearview mirror where most visors don't reach.
(Answered July 26, 2002)