The other day I glanced up and noticed what appeared to be wavy lines on the sunroof. These lines looked like sand dunes look when viewed from an airplane. At first I thought it was some kind of interference pattern but on closer inspection it turned out to be deposits on the inside surface of the sunroof.

I'm assuming the deposited material came from the outgassing of the ubiquitous plastic in the car.

The mystery is this... why did the deposits form wavy patterns instead of uniformly coating the sunroof?

Has anyone else noticed this? Any explanations? My theory is that it has something to do with charged particles...

 

It is probably due to the force of the air conditioning blowing on it, much like wind on sand dunes.

 

Did you happen to have on polarized sunglasses?

 

I noticed this recently too.

James

 

Does it have any tint (even factory stock)? Are you wearing polarized sunglasses?

After we had our windows tinted, if you wear polarized sunglasses, everything looks like its a bunch of wavy lines ... some yellow, some other colors, very sick looking.

Take of the shades and ... all is normal

 

This has nothing to do with polarized light.

It's definitely a residue of some kind because I can easily smear it. I haven't cleaned it off yet -- I'm trying to solve the mystery first and don't want to get rid of any clues!

fwiw, I had another theory today involving standing waves but decided that was too far fetched...

And I'm glad to learn that this has happened in at least one other person's Mini!

 

you will also notice this effect when viewing rear windshields and sometimes side windows when wearing the aforementioned polarized shades...

its completely normal, and has nothing to do with any removable residue...

 

You're right! The effect you mention is related to polarization and has nothing to do with a removable residue. Anyone who has worn polarized sunglasses while driving has probably noticed it.

But, in this case, there is definitely a removable residue because I can easily smear it with a finger. Hence the mystery!

 

They sound like "sandwaves".