I walked out to my car after lunch today and at a certain angle (45 degrees or so) I noticed a checkerboard like design of lighter and darker spots in the window (before the anyone says it, yes theyre clean)... has anyone else noticed this, I was curious if this is from the tint that comes in the glass from the factory (no after market tint on there yet)

 

Were you wearing sunglasses? Polarized sunglasses will give that affect on car windows.

 

Yup. I got them too... Have noticed them before on other cars as well... Points to whomever gives the good explanation.

My guess is that it has to do something with the fact that the glass is designed to shatter into a million pieces as opposed to... breaking like a mirror in the event of a crash.

Just a thought...

 

I have that too. Sometimes you can see it, other times you can't. It's normal. Most cars have this. I forgot what it was for.

 

nope, left them in the car

 

Don't most of cars' windows look like that? I wanna know why, too.

 

I believe this is called Sun Glass Windows and it comes directly from the Manufacturer. Just recently had this been added to higher end cars.

 

^--- I could be wrong but I wanted to give it a shot

 

I did a little reading on a BMW forum and it seems to me that the sometimes visible checkerboard pattern is due to the glass being polarized... Depending on the lighting conditions, etc... it would explain why sometimes it is visible and sometimes it is not...

(if I am right, do I have to give myself rep points?) LOL

 

The pattern is caused by stress when the glass is bent. The tinting in the glass emphasizes the stress lines. Yes, it is sometimes more visible with polaraized sunglasses, but can also be seen when the sun/light is at a particular angle. If you see a break in the pattern it is likely the glass is weakest at that point.

 

"The pattern is caused by stress when the glass is bent. The tinting in the glass emphasizes the stress lines. Yes, it is sometimes more visible with polaraized sunglasses, but can also be seen when the sun/light is at a particular angle. If you see a break in the pattern it is likely the glass is weakest at that point."

Huh? Without going into great detail... And being polite...



Where on Earth did you get this info?

 

did you also happen to notice the safety plastic laminated in the front windshield? you can see what i mean by looking through the windshield at night and focus your sight on some neon lights about 50 yards out. you'll see fringing occur at the edges of the neon.

this is especially annoying at night with on-coming traffic. their lights become very diffracted which in my eye is "glare".

 

I was with you on this and then did some research ... Rexorg is correct .. stress (as is so common this time of year) in this case is caused by taking a multi-laminate glass and shaping it to fit the exterior. The multiple layers "flex" (probably not the right word, so any engineers on this forum can feel free to tech this up) at a different rate, leaving stress points. This is most noticeable when wearing polarized sunglasses, but it is not a result of polarization of the windshield.

And since I thought Rex was full of shite and have now been sufficiently humbled .. points for you Rex and my humblest apology!

 

Normal

 

The pattern is caused by stress when the glass is bent plus tempered process. Most of cars' windows look like that, cause safety plastic laminat only in the front windshield rest is tempered.


It's on all your windows , just walk around a car and read on each glass in a corners.

 

Huh..

"The multiple layers "flex" (probably not the right word, so any engineers on this forum can feel free to tech this up) at a different rate, leaving stress points."

The "checkerboard" seems too perfect for stress lines... Not to mention they are interlaced in two directions...

Also, I was not aware that the side and rear windows of many cars were laminate glass... They are tempered glass usually. That being said, I did just read that there are a number of luxury cars that are coming with laminated glass all around!

http://www.chicagotribune.com/classi...sifiedcars-hed

What we need to know now, is whether the Tl has laminated side windows or tempered side windows!? Has anyone been in a crash here??? Or broke their window? Did it shatter into 1000 small pieces or spider and crack, but remain in one piece.

(Being a FF/EMT this laminated side windows thing is new to me... We typically use a spring loaded center punch to break out side windows in the event of a crash... This simply will not work on laminated glass. I will have to tuck that little nugget of info in my little noggin...)

 

For these stress lines... Your thought that the side windows are laminated is not correct actually...

"A manufacturer sandwiches a sheet of vinyl between two sheets of shaped, annealed glass (a strong glass formed by heating, bending, and slow cooling) to form windshield glass. It’s called laminated safety glass. The glass maker bonds the sandwich together by applying heat and pressure in a special oven. The surface can withstand great impact, but, if it breaks, the broken glass pieces stick to the vinyl and don’t fly around.

Why safety glass crumbles instead of shatters is a property of monolithic tempered glass usually used in side and back windows. By monolithic I mean a single homogeneous, solid glass sheet. Tempered glass isn't used in windshields because it could obscure forward vision when it breaks into small pieces.

To make tempered glass, the manufacturer heats glass, raising its temperature to 1200°F (650°C). The maker pops the glass out of the oven and cools it fast (to 500°F or 260°C) by blasting cool air over the surfaces. (That’s the trick: different cooling rates inside and out. The rapid cooling stresses the glass.) The center mass then cools more gradually, compressing the surfaces and edges as it cools and establishing a tensile stress in the glass midplane. The compression strengthens the outside faces significantly. The differential cooling establishes a residual stress pattern in the glass."

Found this as well "The pattern you see in back window glass is created from the cooling air jets when the glass is superheated and rapidly cooled during tempering. Since the surface cooled at differing rates because the air jets create a more focused (cool) spotting, the material's density is different from rest of the glass surface. "

If the checkboard is there because of the "stress lines," the side glass on the TL is tempered, not laminate... (Unless there is laminated and tempered glass! ROFL)

 

DarkWraith33's reply is right correct.

I have not been in factories that make windows or windshields for cars, but I've seen the manufacturing process for glass lids for cookwares. The process is how DarkWraith33 explained it.

For quality inspection we actually use polarizing lenses so we could see the stress points patterns. If the pattern is uniform then the quality is good. Sometimes some factory's manufacturing is not as good and the stress pattern would be like the checkered look, but distorted in some areas. Sometimes the distortion would be so great you would recognize that it's suppoed to be a checkered pattern.

These patterns are indeed brought about by the tempering process, heating the glass in a mold so it will soften and bend into the correct shape, then cooling it wth air jets for it to settle into that new shape. This process also makes the glass stronger. It will now be resistance to sudden temperature changes and hard blows to the glass. It won't be undistructible, but it would be better than non-tempered glass.