Why are there small black dots on your windscreen?

We all recognise them, but have you ever stopped to think what the little black dots on your windscreen do or why they are there? As it happens, they serve a few important purposes.

The solid black band around the edge of your car window is actually called a ‘frit’. The frit is ceramic paint that has been baked into the glass during the production process, this means that it cannot be scraped off.

One of the frits’ main jobs is acting as a filter to prevent UV rays from damaging the urethane sealant that holds the glass into place.

If the frit wasn’t there then the sealant would be more exposed, resulting in gradual deterioration over time. This would increase the chances that the window becoming displaced which would be very dangerous for any drivers or passengers.  

Not only does it protect the sealant and keep the windscreen in place, but the frit also provides a rougher contact point between the glass and the car frame allowing for the adhesive to stick better to the surface.

The recognisable halftone pattern holds two other purposes. Firstly the fading dots help to even out the heat distribution during the manufacturing process called ‘baking’.

Without the dots, there would be too much heat concentration in the black edges causing visual distortions to the glass.

The other purpose is that it is more aesthetically pleasing for the dots to seamlessly fade out into the glass. This is why there is a slight gradient if you look closely. Dissipating black dots make the frits easier on the eye than a solid black border. The solid black colour also helps to cover up any marks left by the adhesive.

However, this information does not explain why there is a large concentration of black dots around the base of the rearview mirror. This patch of dots is called the ‘third visor frit’.

The third visor frit helps to defuse the sunlight out of your eyes when you’re trying to look at your rearview mirror. A simple yet very effective feature that you may not have been aware of.