need your expertise

J

jaycoop

I have been fighting the battle of the impurities in my air supply, but depending on humidity, I still get imperfections....very little orange peel, thanks to the guidance offered on this site, but I do get the little pimples/water/oil spots....at least that's what I think they are. In a cross section, do these go to the bottom of the coat or do they float somewhere above the bottom of the coat, so that you don't have to sand all the way to the basecoat to get rid of them - especially if it is in the first coat of clear? You experts might get a kick out of this, but I'm trying to understand the science of the 'paint pimple', so that I will be prepared for the color sanding phase (using 3 coats of UV clear over SPI black base)
 
oil usually floats on water, eventually after you shake it up. I think one of the hardest things to do is stop when you notice it, instead of coating on top, around or whatever it.
 
If I were to guess I would bet you are just seeing trash. Water will usually show as a void (after 12 hours or so) and oil will usually show as something close to a fisheye. Unless you are painting in a booth and have a perfectly clean panel car etc you are going to see some trash. Standard practice on clear is to sand until the imperfection disappears. This assumes that you have enough clear on the panel to sand and buff and that the imperfection is not so large or deep that it requires excessive sanding to remove. On base you'll want to sand it until it disappears and then re-base.
 
jaycoop said:
I do get the little pimples/water/oil spots....at least that's what I think they are. In a cross section, do these go to the bottom of the coat or do they float somewhere above the bottom of the coat, so that you don't have to sand all the way to the basecoat to get rid of them - especially if it is in the first coat of clear?
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I always get a few of those too, most everyone does.
I believe it's caused from contamination of some sort, on rainy days when I get real clean sprays
they are very few of them. On dry windy days, I get more.
Most times I can sand them out of the clear and buff them away, but not always, it all depends at which coat the arrive.
Most of the time you can't even see them till you color sand the clear.
That's one of the ways I know a panel has been repainted, it looks fine till you start sanding the clear, then you
see some of those little circles. Most painters don't even know they're there.
On really deep ones that are more like craters, sometimes you can fill with a drop of clear and sand/buff it away.
Most of those types have a obvious piece of dirt in the center.
 
Thanks for all the response...what a GREAT site this is.....I sanded out the most pimply piece today and found that they do sand out nicely without tremendous effort.....likely oil/water bits from my 45 year old compressor. I don't have a great environment, paint booth, or compressor.....I would have good ones of all of those if I painted all the time. I do have pretty good method and paint gun, and good bodywork skill, so this will be a showy black car.....not perfect, but will be an eyecatcher (36 Hudson Terraplane Coupe). I know how to color sand and most panels will get that treatment…..but some of them turn out so good that I hate to....gotta love the UV clear!
 
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