What the black dots on your car windscreen are for

Have you ever wondered what the black dots around your car windscreen are for?

Many drivers have probably thought about it, and then quickly forgotten their curiosity.  

Well, the often overlooked car feature actually has a crucial function, and many people don't know what the purpose really is. Or how vital those dots are for safety.

What are the black dots called? And what are they made out of?

The black dots on a windscreen are called 'frits'.

The frit band is enamel that is baked into the borders of the windscreen, parts of the windows and sometimes behind the rear-view mirror during the manufacturing process.

Usually the frit band starts as a solid line before morphing into lots of individual small dots nearer the edge.

What does the black frit band do?

The frit band has multiple purposes.

It allows the adhesive to bond the glass to the vehicle while blocking against UV rays, and help distribute temperature evenly across the screen.

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Because the black frits are made of enamel they create 'etches' on the surface of the glass, making the glass rougher and easier for the adhesive to stick to – keeping the windscreen in place.

At the same time the black enamel helps preserve the urethane sealant (the adhesive) from melting in the sun's UV rays, keeping the windscreen firmly locked in place.

Frits also have another UV role to play; they distribute temperate evenly across the glass to reduce the risk of 'lensing'.

Lensing is when there's too much heat in one section of the windscreen glass which causes straight lines to appeared curved. The optical illusion would distort vision for drivers, so frits are crucial by dissipating the heat from the sun and preventing this, making sure a driver has a clear view of the road.

Why are frits so important?

As we've already covered frits are absolutely vital for safety while driving.

In multiple ways they keep the windscreen sealed in place and stop the windscreen from moving or popping out during an accident (it used to happen).

And they make sure the driver can see the road clearly too – so they might seem insignificant, but you won't look at them the same again.

Do they have any other functions?

Aesthetically frits also play a role because they ease the eye in to the windscreen design. 

Thanks to their halftone pattern they make the contrast between the dark band and the glass not look so jarring.

What about the black dots around the rearview mirror?

This is a more recent addition. 

The black dots around the rearview mirror are called 'third visor frits' and they have one function: to act as a sun visor and block the sun that isn't covered by your visor.

What if the black frit band is wearing away?

Because frits are so important so it's crucial that you keep an eye on their condition.

The pattern is important so if any frits are wearing away or fading then you need them replaced as soon as possible.

No frits, could mean no windscreen – it could fall out of place.

It could also be a general sign of the state of your windscreen.

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