LG-2 Refinish question

[benstang]

I'm a DIY 'er and have re finished about 10 guitars over the years.  I like putting my stamp and a little elbow grease into  my instruments and have always been happy with the results 

I recently picked up a 1951 LG-2 that had previously been refinished ( its already been done - so no need to tell me NOT to do it 😗).   Some pretty bad "relic" work had been done with an exacto knife ? to simulate lacquer cracks and I decided I didn't want to live with it that way.   I've carefully sanded back the finish and found that many of the cuts go a little ways into the wood.    Does anyone have any advice on how to proceed?  My plan is to bring it back  as close to the original burst finish as I can get to.  The black outer ring doesn't worry me too much but there are a few scratches in the  lighter areas in front and behind the bridge that are filled in with some darkness and will look like crap through the new finish.

I expect these can be sanded out as they aren't super deep, just not sure how much wood I can remove safely.     I'd greatly appreciate any tips, tricks, advice on this one.   pictures are the area just in front of the  bridge.  The condition behind the bridge is similar.  Should I keep sanding?  I tried soaking the black lines with some lacquer thinner on a q-tip but it did not really help.

 

 

 

[jedzep]

Have you considered sanding it down to blonde, like an LG3 would look. I stumbled onto an abused '36 L00 and went all the way with it. It's superlight and thin topped, but plays and sounds bright and alive. I sprayed multiple coats of flat Mohawk lacquer.

[benstang]

Looks great.  I have thought about going all the way to a natural finish, but I'd still need to deal with those scratches.   How much sanding did this guitar need?  Thanks  

[Leonard McCoy]

How thick is the top currently? How well is it braced? That determines how much you can sand away without risking the integrity of the top.

[benstang]

The top measures .011" at the back of the soundhole - the only place I can get a good measurement.   And the bracing is (as far as I know) standard X-bracing for a 1951 LG-2.  The bracing all seems intact from wiggling it - nothing is loose enough to move, and tapping around the soundboard does not yield any loose  noises either.   

The guitar is not particularly "lively" or reverberant when played - but thats another whole can o' worms I think.

thanks for your help.

[jedzep]

The thickness of my top, at .08 still seems substantial, despite the abuse done by the lutherie students. I wouldn't want to risk a thinner one. The lines would likely disappear if you took another .01 or .02 off, but before you entered into a mod like this, you would need to have the bridge and guard pulled so you could reshape the entire face of the top, and have a delicate hand with your random orbital, eventually sanding by hand with something like 5000 grit.  You'd then apply lacquer with the bridge off, and have a qualified luthier re-shape the underside of the bridge to match the new top contour, which hopefully you wouldn't significantly alter.

Looks like a nice straight grain on the section you show. It would be nice to see a shot of the entire top. The LG2 is a sturdy build, so I wouldn't expect a big time open voice.
My sanded and re-lacquered '36 sounds noticeably brighter and open than my original '35, with classic burst. is it the thinness? who knows.

Edited December 25, 2020 by jedzep

[j45nick]

It is very difficult to do this job properly without removing the pickguard and bridge. At the very least, the pickguard should come off.

I did a similar job many years ago, when I stripped the cherryburst off the top of my original 1950 J-45 after Gibson re-topped it and had sprayed a cherryburst on the new top, rather than the traditional sunburst.

In that case, I did a careful chemical strip of most of the top, properly masking everything. I removed the pickguard but left the bridge on. 

I block-sanded the top down, probably starting with about 150  or 180 grit, moving to 220, finishing  with 320 . But that top was still pristine when I did this job--no deep scratches to deal with.

The hard part was working around the bridge, but it can be done. Small custom sanding blocks can be made using things like tongue depressors and paint stirring  sticks. You can use spray contact  cement to put whatever grit paper you want on your stick, then cut the end to shape to work around curves. Tongue depressors or craft sticks are thin enough that you can bend them easily to keep the sandpaper parallel to the surface as you work.

If you are comfortable with fine furniture techniques, you can use ultra-sharp cabinet scrapers to work flush to the edges of the bridge. If you aren't comfortable with a cabinet scraper,  you can do just as well with single-edge razor blades used as scrapers.

If it is a '51, it should have a rectangular bridge, which is fairly easy to work around, although you have to be really careful not to carve grooves sanding parallel the the ends of the bridge wings.

You can tell how it is going to look when finished by wiping the top with a rag dampened with mineral spirits. This will show how any remaining scratches will look under the lacquer finish.

Spruce is pretty much the softest wood I have ever worked with. Fortunately, I had a lot of practice working with it when I was young, since the wooden sailing yachts I rebuilt had Sitka spruce spars. I've also restored massive amounts of teak and mahogany joinerwork using pretty much these same techniques. It can be done, but requires a lot of patience.

You may not get 100% of the scratches out. If some are there that still have old finish in them, you can probably remove most of that with paint remover applied with a cotton swab, then removed with clean swabs. Wipe down with mineral spirits after. Do not try to hand sand out local scratches. You will put divots into the wood.

Back then, there were no spray cans of nitro lacquer. I brushed on semi-gloss or satin Deft clear wood finish, which is a nitrocellulose brushing lacquer. Today, I would buy spray cans of nitro lacquer from Stewmac to do the same job. I would use either satin or semi-gloss clear , depending on the effect you are after. Those less-glossy finishes are more forgiving to apply, and show fewer flaws than a high-gloss finish. This is also a 70-year-old guitar, so it doesn't need to look like it was born yesterday.

It would be much easier to turn this into an L-3 than to try to replicate a good sunburst. Those require a lot of practice. Clear lacquer is fairly easy to work with.

How thin can you go on the top? Pretty thin. it is not unusual to see a top thickness of   .10", sometimes even slightly less.

Having said that, you want to sand off as little as required to remove as many of the scratches as possible.

 

Edited December 26, 2020 by j45nick
correction

[jedzep]

Though I did my first sanding with a small Bosch random orbital machine, as I mentioned to you, it's a tool that I handle often, so I'm comfortable keeping it backed off. It doesn't take long to do irreversible damage with this method, however, so I'd agree with Nick's use of soft block sanding.