On my bridge windshield there appears to be spotting or some sort of distortion? I can't clean it off and it depends on the direction of the Sun as it sometimes goes away? Any cure for this problem - besides a new glass??
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Windshield distortion?
- Thread starter Capt. Art
- Start date
If it's a spotty pattern that is visible when wearing polarized sunglasses what you are probably seeing is birefringence from the residual stress pattern in tempered glass. This is a very common phenomenon and there isn't anything you can do about except take off the polarized glasses. You may also see it in the rear glass in a car - best seen when looking from the inside out or looking at the rear view mirror.
Here's a simple test if you see it when you have your sunglasses on - turn your head sideways as you watch the pattern, so that the lenses and your eyes go from left right relative to the ground to top bottom. Does the pattern change ? Do the dark and light areas reverse? If so, then it's what I described above.
edit - After just driving around and noticing the pattern in the rear glass via the mirror I was reminded that the angle of the incident rays makes a big difference. The birefringence effect is maximized with a low, direct incident angle to the surface. On my wife's car this happens only when the sun is behind the car and later in the day. On my Sea Ray 330 DA the wrap around windshield is rather steeply raked, and the residual stress must be extreme (as would be expected with the shape) because the pattern is nearly always visible through my Maui Jim's.
Here's a simple test if you see it when you have your sunglasses on - turn your head sideways as you watch the pattern, so that the lenses and your eyes go from left right relative to the ground to top bottom. Does the pattern change ? Do the dark and light areas reverse? If so, then it's what I described above.
edit - After just driving around and noticing the pattern in the rear glass via the mirror I was reminded that the angle of the incident rays makes a big difference. The birefringence effect is maximized with a low, direct incident angle to the surface. On my wife's car this happens only when the sun is behind the car and later in the day. On my Sea Ray 330 DA the wrap around windshield is rather steeply raked, and the residual stress must be extreme (as would be expected with the shape) because the pattern is nearly always visible through my Maui Jim's.
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quote:
Originally posted by divedaddy
birefringence from the residual stress pattern in tempered glass.
That's way too big of a word for me...LOL