How to clean bad paint contamination/stain
Something horrible got on the paint on my 2007 titanium silver BMW. I had parked it for a week in the Philadelphia airport parking garage, to keep it protected from the weather. When I got home, I noticed a horrible goober stain on the hood, and I'm assuming it got there at the airport since I didn't notice anything flying onto on the road. It appears that a big plop of liquid hit it on the flat center of the hood near the windshield. Some of the plop ran and left a trail down toward the grill. It is an opaque gray, flat, chalky color. The surface texture feels like a slate blackboard to the fingernail. It is clearly raised above the paint layer, and doesn't seem to have etched or eaten into the paint. I was able to remove a good bit of the surface with a clay bar lubricated with detailing spray, but a very ugly, still mostly opaque stubborn thin layer remains. I can very carefully and gently scratch it with my fingernail and remove this stuff. It would take forever to remove this jumbo pancake size paint stain with the fingernail method, the feeling of a slate blackboard on my fingernails would kill me eventually, and I don't think my fingernails are too good for the paint. But I don't want to attack it to violently with the clay bar, since at this point the clay seems to have removed the stuff well but isn't taking it down much further. I also don't want to use a cleaner wax or a polish, because I don't want to remove ANY clearcoat on this brand-new car. Everybody says, take it to the dealer or a detail shop, but I'm afraid they'd just hit it aggressively with a polisher and remove a bunch of clear. I've done a good bit of high quality custom paintwork on vintage motorcycles that I've restored, and I know enough to respect good paint and treat it right and not rush a job or do a job with the wrong approach or tools.
What would you all recommend?
Oh, I tried letting a microfiber rag soaked in quality car was liquid sit on the contamination, but it didn't loosen it. Neither did a good quality bug/tar remover. Thanks in advance for any ideas.
when bmw sprays those cars they bake them after spraying at 200-300 something degrees...when that car hits the show room floor..that car is cured.
Anything you would do a year from now is the same thing you can do now, waiting isnt going to make the situation any better.
Just sand the spot off with a little 2000 sand paper and polish it. Your not going to remove enough clear if any to damage or alter the finish.
I agree with Pane2k sanding with 2000 wet sandpaper can cut a little of the clear down then the dullness caused by the sandpaper can be polished out. If you sand and polish and the stain remains you will need to have the hood repainted. If you can't handle this yourself a good detailer or body shop can probably help but you want to let them know that you understand the process so they won't try to sell you more than you need.
If it was raining
there's a pretty good chance all you have is a lime deposit from a leak in the parking structure. A chemical like Lime Away or CLR will react instantly with the contamination - when the contamination is dry.
I usually water that stuff down three parts water at least and wear gloves follow label instructions etc.
If that's what it is, the stain will foam when the acid hits it. If that happens then just spray that area with lime away just before you wash the car a few times or just go over it and over it a few times till the stain goes away.
If you decide to sand use a very hard block until you get most of the stain off so you don't rub a negative of the stain into the paint.
I'm pretty sure the lime away is going to handle it.
Write back and let us know.
It was lime, and CLR removed it!!!
Robert was right. It was lime, and CLR took it away immediately. No sanding, no polishing. Fantastic. The clay bar removed the top layer, but left a micro ugly opaque layer that wouldn't budge. CLR took it right away. Thanks, Robert!!