Z4 Coupe marks on black part of rear window

[beatle boy]

Hi, As we all know the Z4 Coupe has a problem with trapped rain water on lower part of rear window. I have noticed that following the recent rainy weather there appears to be marks on the black part of the window along the bottom edge where water has laid.
I have tried cleaning with glass cleaner but can't shift the marks . Its almost as if the marks are inside the glass rather than on surface.Has anyone had this problem and if so was it possible to sort it.

 

[Anonymous]

I garage my car but, I have noticed when washing it that the water collects and does not drain in that area. Try to clean the window with some claybar to see if that helps remove any deposites from the water.

 

[beatle boy]

Thanks Jason , I will try that

 

[Bing]

Buy a roadster - comes with roof drains built in oke: