Sanding Question

[Darryl Young]

Yesterday, I finished sanding all the old finish off the back of the 00 I'm building. If you don't remember, I started spraying finish and after 3 or 4 coats my compressor broke down, then after getting it up and running I was a little panicked and sprayed coats too close together and got sags in the finish, and then I ran out of finish before building up enough coats. Finally, I sanded through the thin finish while trying to level sand the sags I had created. Bummer. So I decided to sand everything except the side back down and refinish. The sides look pretty good.

It took forever but I finally sanded through to bare wood removing even the z-poxy pore filler (not sure if that was necessary). The mahogany back looks nice but with a light at a low angle I can see scratches that are roughly 45 deg to the grain. While the finish/zpoxy was still on I sanded every which direction. But I sanded with the grain (220g) for quite a long time near the end.

So should I worry about these cross grain scratches? I really don't want to remove any more wood from the back but I will sand more if the cross grain scratches will show up under the finish. What do you think?

[B. Howard]

Do they light up when wet with solvent like DA or naptha? If so they will show in the finish, if not you are good to go.

[Darryl Young]

Thanks Brian. I'll check when I get back home from work.

[nehsgolfer]

I have sanded the finish off of the top of my guitar after 10-12 coats of lacquer and it is a pretty tough job. My question is since it takes so much work to do this, why should I be concerned with sanding through the finish when I am leveling and wet sanding a finish? It just doesn't seem like that would ever happen.
Thanks

[Darryl Young]

nehsgolfer, I'm guessing how difficult it is to sand through the finish is a function of how thick your finish is and how level the wood was before you started......and what grit sand paper you are using.

[MaineGeezer]

As an alternative to sanding, how about stripping the finish with lacquer thinner? Needless to say, one would want a good vapor mask and no source of ignition nearby, but in my experience lacquer washes off fairly easily with lacquer thinner.