Rain Spots: Why So Tough ??

HondaMan

HondaMan

2004 Civic EX magnesium
I mentioned a few weeks ago that I accidentally got some rain spots -- actually, hose water spots -- that I let dry in the sun. I couldn't believe how tough it was to get the stuff out: I tried Autoglym on the glass, glass cleaners, claying, AIO on the glass/paint -- it would have taken me about 6 hours to do the whole car from scratch to get it back to where it was.

Well, after some weathering, it appears that the rainspots on the car body have more or less faded....I guess the elements wore them down just like all those acryllics and resins I have been applying. My car had a couple of layers of UPP and some AIO as protective covering, so I never thought the spots "burned throught" to the paint below. Still, it looked ugly for a few days.

The glass still isn't great. I'll try and get it cleaned during my final fall wash in a few weeks.

Question: What exactly causes rain spots? And why are they so tough to get out? Of course, any suggestions greatly appreciated (other than spending 3 hours of muscle on 1 windshield. I spent like 20 minutes claying, AIO'ing, and glass cleaning 1 small area of the windshield and it STILL had the spots !!!).
 
Hondaman, I could be way off base here, but I think waterspots are caused due to what is in the water droplet. Stuff like minerals that get left behind in the drop and then when the drop dries, the stuff in the water stays on the paint in the shape of the drop. That would be my guess.
 
Hose water spots are usually more difficult to remove than rain water.
Water from the hose most often contains minerals like calcium and iron. When these spots sit on the paint and dry the mineral deposits are left behind and they are hard. If the sun hits them in this drying process the water droplet acts as a magnifier which causes heat. This can cause the spot to etch into the paint.
To remove the surface spots on glass, I start out with vinegar poured full strength on a rag ... wipe on the glass ... let sit for several minutes ... wipe clean.
If that does not remove the spots, I use a concentrated toilet bowl cleaner. (The acid content is much higher ... So Be Careful ... do not get on hands or metal parts of the car.
I use the same process as with the vinegar only I use just enough of the chemical to lightly coat the glass and then wipe with a damp cloth.
I have used the toilet bowel cleaner on house windows and auto glass without and problems. Also work in the shade.
Just my .02
 
Thanks, Kim & Jared.....I'll try the vinegar and I'm just glad I had multiple-layers on the car to prevent that burn-in effect on the paint you mentioned. My stupidity -- car got wet from doing another car nearby and I never thought to move it to the shade.

I see now there's a big difference between drying in the shade and in direct sunlight.
 
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