Mottled glass

[busdaddy]

Somewhat irrelavent threads seem to be a trend here lately so I'll jump on the bandwagen

What makes VW tempered glass show the checkered or mottled rainbow pattern at some times of the day or under certain atmospheric conditions? I know it's due to polarization but why only VW glass?, of the many, many vehicles I've owned or seen over the years no other glass does it. It doesn't seem to be brand or year specific either, usually it's on the perfectly flat panels but I have seen it on the curved back windows of beetles too.

Just walked past the 71 and it was doing it, brings back memories of a 21 window my dad had when I was little every time i see it and it made me wonder.
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[EZ Gruv]

I see it on other cars when I have sunglasses on.
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1977 Deluxe Westfalia - 2.0L FI Type IV, Completely Original
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[Tom Powell]

If you wear polarized sunglasses, the cockpit windshield will be alive with the mottled rainbow patterns. The pattern changes with pressure differential and airspeed. B737 windshields are five layers, glass, gel, and plexiglas. They are heated and are somewhat flexible. It might be the width of the layers and the angle of the light that make the pattern. And/or it might be the components of the glass mixture. I've also seen the patterns in older glass that was delaminating.

Aloha
tp

[Desertbusman]

You're so far north are you sure it isn't aurora borealis?
Down here we just see sun spots in the glass.
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71 Superbug
71 Westy

[Lil Lulu]

I used to see all kindsa things in the glass. Rainbows, colors, butterflies, dragonflies, angels, Siddhartha, Marx, my stockbroker, John Lennon, Henry Miller, Yogi Berra..............
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1600 stock from '71 bus

'72 Deluxe - Niagara Blue w/pastelwiess Camper Special 2L dual 40 Webers 002

'74 Hightop Weekender "Dixie" 1800 34 Del singles

[patayres]

It's a phenomenon of tempered glass (and a way to tell if glass has been heat treated/tempered). The rainbow/checkerboard pattern is actually a stress pattern from the cooling jets blown on the glass during the tempering process.
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1975 Westfalia Helsinki - 1800 EFI w/ Pertronix
1965 Singlecab - 1600dp

yuthi'so'coro

[greenbus pilot]

I remember seeing that type of distortion in my dads old Mercedes. Saw it in the rear window. Never saw it anywhere else.
Get new glass. See (pun intended) if it goes away.
I'll ask my glass expert guy at work.
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[1977_L63H_P27]

For a while in the 80's Ford rear windows were bad about it. I didn't notice it on other makes. And I still haven't noticed it on my VW's. Peace!
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[corgimama1]

If it's any consolation-I have the same issue with my 2010 Jetta.

[1975 Kombi]

I'm not sure it is the glass but maybe something in the water your drinking.
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Brett

“He’s decieving you boy! Reach into his pocket and take what he’s got.” Mr. Crabbs.

75 Westy auto
03 Jetta TDI
71 SB
74 Westy
Licensed pilot (single engine land VFR)
--
Rust In Pieces: 72 Bug, 73 Bug, 81 Rabbit LS D 2D, 83 Rabbit D 2D, 84 Jetta TD GL, 85 Jetta D, 68 Z28 RS 302, 91 Passat 16v

[lostsailr]

The sad part about replacing my windsheild was loosing that tye-dyed glass look (especially when wearing polarized sun glasses), but the trade off is that there are no scratches, so I can actually see at night now!
My body shop guy got me a new one for around $200...good deal?
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[86rocco]

all three of my sciroccos did this, one '84 and two '86s without polarized sunglasses.

Every other car I have owned which is oh about 8-10 vehicles required polarized sunglasses to get the effect.

If I were to tell you why glass does this, someone would spontaneously combust and I do not want that on my conscious or I don't know why this happens in some glass and not others.

[Trailjunky]

I came across this thread on accident while searching for an unrelated topic. Lo and behold it solved a curiosity that I'd been having for a few days. I kept noticing spots on my windows that I'd never seen before. After reading this thread I realized I'd just bought a new set of polarized shades. Duh.

[thewalrus]

The rear window on my bus look like the picture above but a lot closer and more reddish. Never a problem with the front windshield though. It's just real pitted
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'73 Transporter 1.7L Dual Carb

[Kirk]

I bought a SUPER CHEAP pair of sunglasses one year when I took my family to Sea World. It was messing with me bad in our 2006 F150, but I didnt know what it was. Subsequent and less cheap pairs of sunglasses havent had it. Dunno.
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[dan macmillan]

[srfndoc]

Polarized sunglasses as somebody already mentioned.
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[SGKent]

and here I always thought it was the spirits of the bugs I'd hit embedded in the glass.
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