Why are there black dots on the edges of car windows?

If you look closely at the windshield or rear car glass, then along the edges of it you can see a narrow black strip applied around the entire glass and turning into black dots. These are the so-called frits - small droplets of ceramic paint, which is applied to glass and then baked in a special chamber. The ink is stencilled, so the black stripe is sometimes called silkscreen and the frits are sometimes called silkscreen dots. Under the influence of high temperature, the paint forms a rough layer that is not washed off with water or cleaning agents.

A layer of paint with dots is needed to protect the sealant

The main function of ceramic paint is to protect the polyurethane sealed adhesive. The sealant sticks together the glass and the car body, preventing moisture from entering the interior. The weakness of this adhesive is that polyurethane loses its properties under the influence of ultraviolet light, which means that the sun's rays are detrimental to the sealant. But under a layer of silk-screen printing, the sealant is inaccessible to the sun. In addition, the adhesive adheres better to rough paint than to a smooth glass surface.

Dotted paint layer makes the glass more attractive

Frits also serve a decorative function. The sealant cannot be applied evenly, so sloppy streaks and uneven application of glue would be visible through the transparent glass. A strip of black paint perfectly masks such defects. The frit pattern itself, when the black strip breaks up into small dots and gradually fades away, also has its own task. As the gaze moves across the frits, the eyes are less strained due to smoother focusing.

Frits are sometimes applied to glass to protect the driver.

The third task of frits is to protect the driver from blinding. The black dots behind the center rearview mirror act as front sun visors. When the driver looks in the mirror, he will not be blinded by the rays of the sun falling on the windshield. In addition, the black paint around the edges of the curved windshield prevents lensing effects that can make objects appear distorted. Another useful property of frits is to smooth out the sharp light contrast at the junction of the glass and the body. Otherwise, in bright sunlight, the glare effect for the driver would be much stronger.

In a modern car, even such a simple thing as a black stripe on the glass plays an important role. Its production is a complex technological process.