Those black dots on your windows make your car safer. how? | My car and me

For a long time, car windows have had a rubber rim. In older cars you can clearly see this around the front and rear windows. This edge ensured that the front and rear windows became watertight and remained in place. But since the 1980s and 1990s, those “bolted” windows have largely been replaced by glued-on ones. This is standard practice now.

Bonded windows offer many advantages. The design is sleeker, and the aerodynamics are better. Because that thick edge is no longer around it. This also means that the window can be part of the car's body. In other words: the window absorbs forces. This ensures better driving and safer cars.

Of course it would be ugly if you saw glue under the window. Therefore, its edges are covered with black paint. Immediately the pattern appeared with dots. The front and rear windows have black borders, but you also see them on three-quarter windows and glass roofs. This is the case with almost all cars. Not just for aesthetic reasons, but because it is necessary.

Black borders and associated dots are printed on the window. The paint is then applied to the window, making it nearly impossible to remove. The edge is always inside the window. It hides the glue from view and forms a surface to which the glue can adhere better.

The dotted pattern ensures a gradual transition from the opaque to the transparent part of the window, and this transition is related to temperature. The black window pane heats up faster than the transparent pane. Everything that gets warm wants to expand. Also glass.

A glued window cannot move in its seat to absorb heat. This creates additional tension in the glass. This in itself is not a problem: the glass is strong enough. But if the transition between the all-black painted part and the clear part is abrupt, there can be such a large temperature difference (on such a small surface) that the window can crack or break.

The dotted pattern therefore ensures that the temperature difference – more than a centimeter or two – is also gradual. It is enough to eliminate the risk of glass breakage due to this temperature difference. Only in specific situations (on dark tinted glass, for example) are exceptions sometimes made.

The entire automobile industry uses a dotted pattern. This makes sense, because presses (the pattern is printed on the inside of the window) work this way. In theory, you could make another pattern with the same effect, but that doesn't happen.

What sometimes happens is that car designers add illusions. For example, they put an additional graphic on the pasted edge of the window. This actually costs nothing, because the printing pattern has to be made again for each car window. As long as the fee is small, there is no increased risk of problems. For example, Jeep places the silhouette of an old military Jeep in the corner of the windshield of its Renegade minivan, while a Yeti haunts the dark-tinted rear window.

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