The ceiling dissolved on my car. I want it to go away.
June 7, 2011 2:01 PM Subscribe
How best to remove an unidentified mineral substance/residue from the hood of my car?
For several months I parked my car in the basement garage of an old apartment building. There were some sort of occasional water leaks in the ceiling of the garage that dripped onto the hood of my car and left behind a white, mineral-looking substance that has been very resistant to removal. It looks kind of terrible, especially since my car is black. Any thoughts on how to get it off?
Random facts--the ceiling itself looked like it was forming small stalactites over my car, and I suspect my car would have looked the same had it been left there long enough. I don't think the leaks were from rainwater, as the incidents didn't seem timed to rains. So far I have tried to remove the residue with hot water and soap at a car wash; hot water, soap and scrubbing with a towel; and scrubbing with simple green. None have been effective, though you can just barely chip the residue away with a fingernail. Haven't tried anything else yet because I'm wary of ruining the finish.
Thoughts?
For several months I parked my car in the basement garage of an old apartment building. There were some sort of occasional water leaks in the ceiling of the garage that dripped onto the hood of my car and left behind a white, mineral-looking substance that has been very resistant to removal. It looks kind of terrible, especially since my car is black. Any thoughts on how to get it off?
Random facts--the ceiling itself looked like it was forming small stalactites over my car, and I suspect my car would have looked the same had it been left there long enough. I don't think the leaks were from rainwater, as the incidents didn't seem timed to rains. So far I have tried to remove the residue with hot water and soap at a car wash; hot water, soap and scrubbing with a towel; and scrubbing with simple green. None have been effective, though you can just barely chip the residue away with a fingernail. Haven't tried anything else yet because I'm wary of ruining the finish.
Thoughts?
It's probably calcite leaching out of the concrete. Try flushing the deposits with soda (carbonated) water. The carbonic acid should convert the calcite to a water-soluble compound that will wash off without damaging the finish. I have no idea how much flushing this would require, but carbonic acid that's much weaker than soda water created lots of very big holes in limestone.
posted by Kirth Gerson at 2:09 PM on June 7, 2011
posted by Kirth Gerson at 2:09 PM on June 7, 2011
Best answer: Probably a Ca/Mg carbonate deposit, since that is what comprises 'hard water.' I assume it leaked through the pipes (the carbonate salts don't evaporate, hence aren't found in rainwater, and hence your deposit).
Does your building have hard water? If it does, dishes might gain a visible coating after rinsing, and your kettle might be filled with white flakes? If not, I'm probably wrong. If so, you could remove the lime deposits with vinegar since the acid will increase the solubility of the lime by protonating it.
You can also use hot water + vinegar since it will dissolve faster. Better test both of these somewhere inconspicous first.
PS: Just previewed the above two comments. No idea how effective soda water would be.
posted by mostly-sp3 at 2:11 PM on June 7, 2011
Does your building have hard water? If it does, dishes might gain a visible coating after rinsing, and your kettle might be filled with white flakes? If not, I'm probably wrong. If so, you could remove the lime deposits with vinegar since the acid will increase the solubility of the lime by protonating it.
You can also use hot water + vinegar since it will dissolve faster. Better test both of these somewhere inconspicous first.
PS: Just previewed the above two comments. No idea how effective soda water would be.
posted by mostly-sp3 at 2:11 PM on June 7, 2011
It might help if you built a dam around the deposits using modeling clay, or Moretite or something, so the soda water pools up on them, rather than running off immediately.
posted by Kirth Gerson at 2:13 PM on June 7, 2011
posted by Kirth Gerson at 2:13 PM on June 7, 2011
Response by poster: Thanks folks. I will try both of those and report back!
posted by bepe at 2:13 PM on June 7, 2011
posted by bepe at 2:13 PM on June 7, 2011
Best answer: We had this exact problem. I believe the vinegar worked just dandy.
posted by Madamina at 2:16 PM on June 7, 2011
posted by Madamina at 2:16 PM on June 7, 2011
It could have something to do with a leak of hard water, but it's very common for concrete structures to grow stalactites just like caves do; there's a lot of calcium in concrete. And I see that OP didn't say the ceiling is concrete, I just assumed that.
posted by Kirth Gerson at 2:21 PM on June 7, 2011
posted by Kirth Gerson at 2:21 PM on June 7, 2011
Response by poster: Kirth Gerson, I think the ceiling was concrete (I no longer live there). But it was pretty grimy and gross, so I'm not sure. Gonna try some vinegar and/or soda tonight when I get home. It will be nice to not have my car not look like a flock of large birds shat on it. Thanks for the recommendations!
posted by bepe at 2:26 PM on June 7, 2011
posted by bepe at 2:26 PM on June 7, 2011
Best answer: For hard water, you want acids not bases. Try the vinegar, but warm it up first ( warm not hot). Soda will not work well.
posted by bonehead at 3:48 PM on June 7, 2011
posted by bonehead at 3:48 PM on June 7, 2011
You misunderstand, bonehead. Soda water is carbonated water, which is carbonic acid.
posted by Kirth Gerson at 5:32 PM on June 7, 2011
posted by Kirth Gerson at 5:32 PM on June 7, 2011
Hmm. On second thought, my fiance tells me that we took it to a full-service car wash and had them buff it out with whatever solvent they use there. It was in a detailing service that cost about 40 bucks. (We made our landlord pay. Oh, yes.)
posted by Madamina at 9:09 PM on June 7, 2011
posted by Madamina at 9:09 PM on June 7, 2011
Response by poster: Thanks for all the answers. I was able to remove the deposits using a sponge soaked in warmed-up vinegar. It took a little work, but the vinegar eventually dissolved the deposits beautifully. I had also tried using windex, thinking that the ammonia might work, but it didn't seem to have much effect. Maybe not enough ammonia, or not warmed up, who knows. Anyway, my car looks much better now.
posted by bepe at 10:26 AM on June 16, 2011
posted by bepe at 10:26 AM on June 16, 2011
Ammonia in water is basic. That's great for cutting greases, which are slightly acid, but not so good for most mineral salts.
In this case, vinegar works a little better than bicarbonate because the acetate part of the vinegar can help stabilize ("chelate") some of the mineral salts.
posted by bonehead at 11:06 AM on June 16, 2011
In this case, vinegar works a little better than bicarbonate because the acetate part of the vinegar can help stabilize ("chelate") some of the mineral salts.
posted by bonehead at 11:06 AM on June 16, 2011
This thread is closed to new comments.
posted by k5.user at 2:07 PM on June 7, 2011