What Are Those Black Dots on the Edge of Your Windscreen and Four Reasons Why You Need Them

Automologist MAC equips you with the answers in case anyone asks. 

Kids ask the darndest questions. This morning, on the school run, my young un’ asked me why there is a rim of black dots around the edge of the windscreen. I bet you don’t even notice them anymore as you drive to work, but just about every car has them and has so since the early 1970s when motor manufacturers started to use glue to hold your windshield in place. The dots come in a number of shapes and sizes—some round, some angular and some in the name of the manufacturer.

The dots, which are actually called FRITS, are so common and workaday that I bet you never ever asked yourself why they are there, but there is a really good reason—four, in fact—as to why you will see them on just about every car.

So, a Frit is black enamel which is baked onto the edge of your windscreen when they are manufactured. Normally, they will be a solid band around the edges and they gradually dissolve to form a diffused effect. You will probably notice that your other windows have them as well.

The main purpose of the Frits is to serve as a contact point between your frame and glass. The enamel is ‘bumpy’ or ‘etched’, making them rougher and giving them a greater surface area for the adhesive and thus making a stronger bond.

Secondly, they shield the urethane sealant (glue) that is used for the bonding process. In effect, the black enamelling stops the sun’s ultraviolet rays from melting and degrading the glue, and thus helps to keep the glass stuck down and in place.

Next, the dots or matrix are essential to distribute the temperature more evenly across the glass and stop any form of optical distortion, which is known as lensing. Lensing can occur due to the black area heating up much faster than the rest of the glass in the windscreen and will create a distortion effect that makes straight lines look curved—not what you really want when driving. The graduated black dots reduce this effect by dissipating heat more evenly.

Lastly, they just look good and are there for that simple aesthetic reason. From afar, the border from the black edge to the transparent glass is just too harsh. So, by adding a graduated edge of dots that decrease in size, the optical effect creates a soft edge that is far more subtle and thus pleasing to the eye. Some manufacturers use the Frits as a sort of third sun-visor behind the rear-view mirror as well to fill the space that the other sun visors just cannot reach.

So, now you know. I doubt if this information will contribute to the reduction of global warming or bring a stop to the war in Ukraine, but at least when your seven-year-old asks the question, you will be fully equipped to answer.

Have you ever noticed it?