LIT­TLE BLACK DOTS

No, they're not just for dec­o­ra­tion

Reader's Digest Asia Pacific - - Contents - MEGHAN JONES

The lit­tle black dots on car win­dows are more than mere dec­o­ra­tion.

You prob­a­bly haven’t given much thought to the pat­tern of lit­tle black dots on the edges of car and bus win­dows. Sure, they look cool, but do they do any­thing?

Thanks to Jalop­nik. com, we learned that those black dots on wind­shields and win­dows, and the black rims that sur­round them, do have a rea­son for be­ing there (other than dec­o­ra­tion). It has to do with how car win­dows are made – from the 1950s and ’60s on­wards, car man­u­fac­tur­ers started to use an ad­he­sive to hold car win­dows in place, rather than metal trim. This ad­he­sive got the job done, but it wasn’t very aes­thet­i­cally pleas­ing. En­ter the black rims that you see around car win­dows. Called ‘frits’, they (and the dots that bor­der them) are made from ce­ramic paint. The frits are there to hide the rather icky-look­ing – but im­por­tant – ad­he­sive from view. Also, since these painted rims are baked – yes, baked – into the win­dow, they are all but in­de­struc­tible. They hold the glue in place, which holds the win­dows in place.

As for the dots, they are there to make an aes­thet­i­cally pleas­ing tran­si­tion from the thick black lines to the trans­parency of the win­dow. The dots aren’t ran­domly placed; they are po­si­tioned in what’s known as a ‘halftone pat­tern’, get­ting smaller and fur­ther apart as the black re­cedes. This pat­tern is less jar­ring to the eye than opaque black paint jux­ta­posed with trans­par­ent glass. How­ever, even the dots aren’t just there for dec­o­ra­tion. Be­sides their vis­ual ef­fect, the other pur­pose is to pro­vide tem­per­a­ture con­trol. To get the glass of win­dows and wind­shields to be bent the way it is, the glass is heated up. The black-painted glass heats up faster than the rest of the win­dow. The dots dis­trib­ute the heat a lit­tle more evenly, which pre­vents the wind­shield from warp­ing in the heat.

So, now you know!

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