Ellie911

I was wondering if someone might be able to help me to determine the cause of the following problem and offer a solution. I have recently obtained a very clean 1987 Porsche 911 and noticed that when the sun hits the back windshield at a certain angle, a hazy grid pattern consisting of both horizontal and vertical lines becomes apparent. Similar hazy patterns, but less symmetric, can be seen on the passenger side windows. I have used several cleaning solutions on the windows, but have not been able to get rid of these hazy patterns. The previous owner did not smoke, so I don't this that is is contributing factor. I’m was wondering if hazy patterns were caused by deposits resulting from evaporation of some prior treatment used to clean the interior of the car. The interior of the car is black, so if the car is parked in the sun, the inside gets pretty hot. I’m curious to hear what you think.

Thanks for your help....

Anthony Orosco

Sounds like this is something within the glass itself so no amount of cleaning will remove.....most likely.

What may have caused it is something with that pattern (horizontal/vertical lines) being up against the windows. This is only a guess as I haven't seen any pictures and by your description it seems as though regular cleaning hasn't touched the lines so that tells me that it's not an oily film.

If possible post up some pictures.

Anthony

srf506

I've seen some windows show a "blotchy" rainbow pattern at certain angles, especially the tinted ones. I think its light polarizing through the different layers of glass, adhesives and tinting. But it can't be seen inside the car and doesn't appear to be a real issue. I'm wnodering if in manufacturing the glass the adhesive used to bond the safety glass layer together is a grid versus a solid sheet and that's what you're seeing. But its just a guess on my part.

MoeMistry

Like Anthony mentioned, can you post some pics? If it's an aftermarket windshield, you get grid patterns from different manufacturers. On the new Range Rovers. there are verticle lines, almost like fishing line, on the front windshield. Not sure if a safety feature, but it's there.

Irksome

Not sure it's related, but...

I have polarized sunglasses. When wearing them, I can see tons of patterns like you mention. The way auto glass is made seems to put polarization effects into the glass. Some windows look like a waffle pattern, some look like there are lines running through them, etc. All of these effects are kind of 'fuzzy', ie, no sharp lines. Often, you can see them more or less by tilting your head (lining up more with the polarization, or less).

I'll never again buy polarized lenses, but it is interesting to see how much light out there is polarized. If I lean my head right, my radio display fades out, lean left and it gets brighter...

BuddyK

Yep, I have seen the "waffle pattern" on the back window as well.

I also have polarized glasses, and now that I think of it, it's probably when the waffle pattern is noticable.

NoVaGator

it's a combination of the tempering of the glass (which creates "tension" in the glass which consequently polarizes the reflected light at a variety of angles) and polarized glasses.

take two pairs of polarized glasses, turn them at 90 deg angles to each other, and see what happens...nothing.