during wetsand nitro cracks.

[rolloman]

While wetsanding the last two guitars I have gotten some cracks in the nitro always extending from some of the holes that were drilled beforehand like pickguard screw holes. Is this from the water getting in the whole and the wood expanding or something like that.

 

[bagman67]

Sounds likely.  If you are packing or masking the holes with something when you spray  nitro, stop that.  You can sand them out with a pencil wrapped in sandpaper after you're done with your wet sanding.  you can also try waxing the inside of the holes with beeswax or something like that to forestall seepage.

 

[Cagey]

Right. Nitro is generally pretty brittle stuff, while wood isn't. Get the wood wet and it expands while the finish doesn't. Creates cracks. The wood will dry out so it's not the end of the world - it's not going to rot or anything - but you may end up with the results you're getting.

Personally, I do very little to prevent it. First, as Bagman suggested, don't try to hide the holes. Paint the little rascals. Second, don't go batshit with the water when wet sanding. Some guys use a spray bottle to just moisten the surface, others just soak the sandpaper and let it drip for a bit before using it. You don't need to get things really wet. You're basically just trying to keep the paper from loading up and causing scuffs.

 

[Scythes]

I agree with not filling the holes, just sand the overspray in the holes after. I also use thin superglue to seal the edges of the holes, but wax like mentioned is also a good way to do that. Superglue is also a excellent way to fix small cracks or chips in the finish! It will sand and buff out just like the lacquer.