Hello,



For a while now the family car has had very bad looking white buildup on the bonnet and roof. On first sight it appears as though the paint has worn down to white primer in patches, however on close inspection, it seems to be a buildup on top of the paint.



Scratching at the buildup with one`s fingernail reveals the normal paint underneath. What could be the cause of this? Is it possible that the paint is separating into its constituents? I ran water over a bad area, and sanded with 1200 grit paper which revealed the normal paint. Aside from accidentally sanding to the metal in a small area, I noticed this paint appeared darker than the undamaged areas.



Polish does not cut through this layer of buildup. It feels like baked on chalk or something to that effect.



Do you have any idea what this is, and what would you suggest for bringing the car back to acceptable condition? I am concerned that sanding may do more harm than good, and it certainly requires a lot of care as it is too easy to sand down to the bare metal after removing the buildup.



Here are some sample pictures:



The area I sanded with 1200 grit (Note bare metal to the left of the sanded spot, my bad):





General overview of the situation, the damage has not been touched except for an attempt to polish the buildup off:







Background info: The car is around 10 years old. It spends most of its life under the sun and is rarely if ever waxed / polished.



I`d appreciate any advice you have!