Quote:

Real quick question...

I'm sanding my car...plan to start painting this weekend. Do you think 220 sandpaper will show sand marks through the paint? I was thinking that all the coats should cover it up pretty well. I have sanded about 1/3 of my car already.

If it creates a problem, I'll make a quick pass with some 320 or 400.



Somewhere back in the thread I did this little schematic to try to explain what happens when you put Rustoleum/Tremclad/Brightside paint on a surface that is not smooth ( ie 80 grit, 120 grit or even 240 grit )


If you look at my chintsy ascii drawing below, just imagine that you are looking at the surface from a side view. You will notice there are peaks and valleys. The valleys are how far down from the top of the surface that the sandpaper has scratched down to...

A A A A A A A A
\/ \/ \/ \/ \/ \/ \/ \

Ok... now that you have that visualization, remember that these paints are 'self leveling'. Most people make the mistake of thinking that the paint will simply fill in the valleys and bring them up to the level of the peak.

A A A A A A A A
---------------------- Paint fills valleys
\/ \/ \/ \/ \/ \/ \/ \ but peak still there


But what happens in reality is that 'some' paint does fill in the valley, but also a coating adheres to the peak. So what happens is you are playing a game of catch up. Each time you go to fill in the valley - the peak also rises. I guess after 40 coats the two might catch up... but it never really does. And in the end it effects the overall look and shine, gloss and depth of the paint job.

Sooooooo.... the smoother the initial subsurface the better the results you are going to achieve. And as we have said all along... the real magic to this paint job is a direct result of the initial preparation of the body surface.

Now.... imagine a 600 grit surface
with smaller scars and scratches... less valleys

mmmmmmmmmmmmmmmmmmmmmmmmmm < sanded surface

And then imagine if your paint was laid down on it

___________________________ < paint layer
mmmmmmmmmmmmmmmmmmmmmmmmmmm < sanded surface

That concept alone should motivate you to get the surface baby bottom smooth before starting the first coat of paint.

,.

Last edited by Marq; 09/12/07 05:10 PM.