What causes color cracks under the clear coat?

[titan7]

I noticed that a couple of my model series have develop feather-like cracks in the paint color but these are under the clear coat, you can't feel them. A few of these appeared when I was color sanding and polishing. Not sure why 2000 gt paper and polishing would cause the base color to crack, especially under the clear coat?? Anybody else see these type of cracks on older Charvels?

[dg]

Since it happened after sanding & polishing, it makes me wonder whether it's heat-related. Were you wet-sanding? Did you use a power polisher or buffer?

-edit- just saw your other thread. Since you wet-sanded & polished by hand, that probably rules out heat. It was a thought...

[titan7]

I was wet sanding, but even rubbing by hand creates some heat. I am surprised that it was enough to cause paint cracking deep under the clear coat. Oh well, it needed it. I guess the only other thing I could have done was go from 2000 gt to 2500 to 3000gt to avoid more hand rubbing with rubbing and polishing compound?

[Newc]

At what location on the body do the cracks appear?

[titan7]

On the top edge of the large horn.

[Newc]

Hmmm. I was gonna say if it was near the pickups or bridge, you may be exposing a repair (hole patch).

Then again, are you quite sure it's not the clear? You can't always feel finish cracks, even if you can see them.

[Rsmacker]

Sitting out in the sunshine, playing your guitar in the garden?

[ihocky2]

Since you said you were color sanding, I am guessing this is a refinish project. If that is the case I am guessing it is either incompatability between the paint and the clear or you sprayed on too thick.

[titan7]

I will take a photo.

This was not a re-fin, I was only wet sanding out some surface scratches.

[straycat]

Don't wet sand with water you're asking for problems.Use mineral spirits.
Water will get in screw holes/surface scratches and swell the wood causing cracks in the paint under the clear coat.

[ihocky2]

I found even better than straight mineral spirits, is to add a little mineral oil to mineral spirits. Mineral oil completely prevents corning on the paper, but drastically slows cutting when used alone. Maybe a 1:8 mixture allows fast sanding but zero corning.

[titan7]

Here are some pictures as they speak a 1000 words. I check the crack with a 20x mag glass and there is no surface crack, it's below the surface. I wonder if it's caused by the difference in humidity from FL to dry So CA?? I have seen this before on other older poly guitars. I can't believe nobody has seen this before. Only really seen from certain angles.





Either way I could care less as there are no neck pocket finish cracks and at 22 years old she looks pretty nice!



I also tossed in a body shot? Before me, there was no shine on the body dull from thousands of little scratches.