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View Full Version : Paint experts...What causes this???



bjfish11
11-04-2006, 08:30 PM
Ok here is the procedure I went through.
Had all the body work done on a box, primer and was ready for paint.
I start spraying down my base coat and realize on of my corners looks like *** and needs a bit more primer. So I stop with the base coat. Then I shoot some more primer on the box and get the corner fixed. I wet sand it all back down to get it ready for paint AGAIN.
Well, I sanded through some of the primer back down to the original basecoat, but I didnt think it would be a problem. So I go to spray my basecoat again and everywhere I sanded through the primer to the original base coat did this little "crackle" (see pic).
So, what causes this? Has this ever happened to anyone? Its happened to me a couple times, so Im wondering why?

http://img223.imageshack.us/img223/9173/michaelpatino010ft6.th.jpg (http://img223.imageshack.us/my.php?image=michaelpatino010ft6.jpg)

springy101
11-04-2006, 08:36 PM
that actually looks kinda cool, and cant you just sand it down and do it over again?

bjfish11
11-04-2006, 08:39 PM
that actually looks kinda cool, and cant you just sand it down and do it over again?

Nope, it just does it again, and again, and again.
I tried.

dirtye30
11-04-2006, 08:43 PM
you have sime kind of oil or water in your paint or clear. or you have two differant products that have a differant base and will pull away from each other. try using a differant \product.

springy101
11-04-2006, 08:43 PM
even if you put more primer and then paint?

bjfish11
11-04-2006, 08:46 PM
you have sime kind of oil or water in your paint or clear. or you have two differant products that have a differant base and will pull away from each other. try using a differant \product.

But its wierd, because it only happens in the area I sanded through the primer back down to the paint. So it cant be anything to do with oil or water in the paint, or gun, or airline.

And its the exact same base coat that was originally used.

bjfish11
11-04-2006, 08:47 PM
even if you put more primer and then paint?

Well, no. I have to sand it down and re-primer the whole thing. Im trying to figure out what is causing this so I can avoid it all together.

bumpweLL.nYc
11-04-2006, 08:48 PM
before you lay your base take off your fingerprints with prep-sol.

bjfish11
11-04-2006, 08:52 PM
before you lay your base take off your fingerprints with prep-sol.

I forgot to say that I always prep before I lay a coat of anything.

supa_c
11-04-2006, 08:54 PM
Looks like you put paint remover on it...

Chevyaudio
11-04-2006, 09:01 PM
My guess was going to be fingerprints (the oil in them from touching the box after you sanded it) but you already ruled that out.

bjfish11
11-04-2006, 09:03 PM
My guess was going to be fingerprints (the oil in them from touching the box after you sanded it) but you already ruled that out.

Yea, I cant figure it out. It only happens when I have to repaint and I sand through the primer. But it doesnt happen every time. Thats why I find it very wierd. Its not like I change my procedure. Its the same thing everytime. :crap:

candyman206
11-04-2006, 09:23 PM
I'm in auto body right now. This happened to a kit car that we had to color match. I don't know what it is called but it will keep on happenning until you sand it all the way down. THe parts you cut into past the primer are now going to keep on getting softened by the new paint. So it's just gonna be a whole mess if you don't just start all over again. Sorry for the bad news. It's something related to being THERMAL PLASTIC, which is something like ice and butter you could keep on melting it but THERMAL SET things can never be put into original form. THe pain is THERMAL PLASTIC is constantly gettin melted by the new paint that has solvent in it.

bjfish11
11-04-2006, 09:25 PM
I'm in auto body right now. This happened to a kit car that we had to color match. I don't know what it is called but it will keep on happenning until you sand it all the way down. THe parts you cut into past the primer are now going to keep on getting softened by the new paint. So it's just gonna be a whole mess if you don't just start all over again. Sorry for the bad news. It's something related to being THERMAL PLASTIC, which is something like ice and butter you could keep on melting it but THERMAL SET things can never be put into original form. THe pain is THERMAL PLASTIC is constantly gettin melted by the new paint that has solvent in it.

It doesnt do it EVERY time, thats why it is very strange.
But thanks a lot for the info. I guess from now on, if I ever have to repaint, and sand back down to the original basecoat, I will just shoot some more primer before attempting to paint again.
Thanks again for the info.

lukedogg
11-04-2006, 11:28 PM
was the part previously panted? Are you sure the primer is compatable with the paint you are using? I had this happen to me when I was painting my Dad's truck. I had to sand through the sealer and I just sprayed a 1 part primer over the parts I sanded through. But since the sealer was 2 part, I had the same effect you are. So I just resealed the fender. This fixed the problem.

bjfish11
11-04-2006, 11:54 PM
ITs the same primer and same brand of base coat I use on every box I build. So I would say they are compatable.

Hustler904
11-05-2006, 03:20 PM
like candyman206 said,strip it all back down,I do bodywork also,not a painter,but thats definitely a reaction from some kind of oil or contaminant in there,looks like some sort or oil making the primer not have any adhesion,I bet you can take an air blower to it and it'll just start flakin off

Mitch86
11-05-2006, 05:37 PM
I also do body work. And I would agree that there is something on the surface keeping the paint from sticking there. I would think you could sand it down enough to get whatever residue off and prime/paint. I'm no paint expert though..

lilmaniac2
11-05-2006, 05:41 PM
^^ im with them

bjfish11
11-05-2006, 07:26 PM
I ended up sanding everything off and starting back with the primer. Wasted some more materials, but at least I wasnt out any additional time if it didnt work out right.
Just got in from getting it painted and cleared. Turned out nice, just one hell of a headache.

Hustler904
11-05-2006, 07:31 PM
yea,sometimes stuff like that happens,atleast it didnt happen all over the whole box

bjfish11
11-05-2006, 07:33 PM
yea,sometimes stuff like that happens,atleast it didnt happen all over the whole box

It might as well have. I reworked the whole box anyway. ;)

Hustler904
11-05-2006, 07:40 PM
thats kinda good that you did,alot of times what can also happen is the primer soaks through,which means on alot of cars we work on at our shop you can see the primer rising through the paint,not sure how it happens but atleast it worked out for ya this time and didnt happen again

candyman206
11-06-2006, 06:19 PM
thats kinda good that you did,alot of times what can also happen is the primer soaks through,which means on alot of cars we work on at our shop you can see the primer rising through the paint,not sure how it happens but atleast it worked out for ya this time and didnt happen again


This is what I was talking about when the paint is softened by a solvent. Ti jsut happens to the areas that have been cut to a different layer with sand paper.