What are those ‘spots’ that I see on car windows when I’m wearing my polarized-lens sunglasses?
Automotive safety glass is stretched in such a way as to make it break into little bits. Those spots are a result of that. Usually, the molecules in glass are randomly oriented, so no polarization effect occurs. The stretching changes that.
We had this same question a few months ago, with more answers. I’ll search up the link once board is moving at reasonable speed again.
BigDaddyD – Thanks for the response. It doesn’t quite explain the checkerboard effect that I see, but it’s a start.
Chronos – I searched the SDMB and the column archive and didn’t come up with anything. A link would be appreciated. Did that thread or column also explain why Pontiac minivan windshields look metallic purple through polarized lens?
If Chronos doesn’t beat me there:
You’ve got this thread:
http://boards.straightdope.com/sdmb/showthread.php?threadid=36870
Which, in turn, links to this thread:
http://boards.straightdope.com/sdmb/showthread.php?threadid=28782
(and I threw this one in for good measure: )
http://boards.straightdope.com/sdmb/showthread.php?threadid=12439