Important reason why there are black dots on your car's windscreen

The world of design is full of surprises, with many things which seem innocuous actually serving important functions.

And one such design feature is actually something which you may well look at nearly every day without realising.

You've probably seen it without really noticing it or paying much attention: this is the little black dots design on the windshield of your car.

You know the ones, that start out as a solid black line before becoming progressively smaller and more widely spaced until the design melts away completely into the windscreen.

Surely, you probably think this is just some way to make the car's windscreen look a bit better?

Well, you would be wrong to think that.

In fact, those seemingly unimportant little black dots actually fulfil a function in the car's design.

So, what is it?

It's a couple of things actually.

The black dots are called the 'frit', and are made up of a rough-textured ceramic paint. This surface provides a better grip for the glue which holds the windshield in place.

Josef Lindau / Getty

Not only that, but the glue would degrade over time if it was exposed to UV light, and the paint works to shield it from this and make it last longer.

A blog post from DeDona Tint and Glass explains: “The modern windshield is a marvel of engineering, and dare we say one of the most underappreciated components of a vehicle. Part of that engineering involved how the windshield is bonded to the frame.

“While the inward facing side of the frit allows adhesive to bond to the glass, the outward facing side of the frit acts as a shield against UV radiation in order to protect the adhesive bond, which would otherwise be weakened by continual exposure to direct sunlight.”

Pretty smart right?

But that only explains why there's a black stripe around the side of the windshield, not the tapering dot pattern.

So what does that do?

Well, having the paint round the edge can create a problem in the manufacturing process called 'lensing'.

Denis Torkhov / Getty

While being made, the glass in the windshield will be exposed to temperatures as high as 700C, or just under 1,300 Fahrenheit.

The problem is that having a line of ceramic paint round the side means that the heat would be unevenly distributed over the surface of the windshield, which is a lot more critical at such high temperatures.

This could lead to 'lensing' on the surface, which is exactly what it sounds like.

While lenses are very useful at distorting light in glasses, contacts, microscopes, and telescopes, making things appear substantially different than they are is definitely not something you want in a car's windshield.

The solution? The dots!

By tapering off gradually the dots blur the line between the solid ceramic paint and the clear windscreen. This means that the heat is more evenly distributed, and lensing is less likely.

And there is one more function as well - they look nice!

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