Spraying lacquer over poly....?

[Allan Lang]

I have an early 80's tokai Les Paul, a nice electric but it was knocked over one jam night and the back of the headstock was slightly cracked. I believe the finish is polyurethane (doesn't soften with alcohol). I opened up the neck with clamps, injected yellow glue and clamped. Worked very well. But there was a ridge at the glued crack joint. I lightly sanded the fixed crack but had to go to bare wood to get it smooth. The size of the bare wood spot is a fifty cent piece or bigger on the back of the neck with the original gloss poly finish sanded dull a few inches in-front of and behind the bare spot. I stained the bare spot of the mahogany neck with Mohawk penetrating stain (transparent) NGR alcohol based. Now since the neck is gloss poly, I don't believe I can spray lacquer over it....? I will need to shade the material I use to hide the fix too. 

Can I add the Mohawk stain to poly to shade if use poly, will the poly stick to the old poly, can it be buffed? I assume I can't use lacquer over the aged poly...? Any suggestions on what material to use? I have a lot of experience in spraying lacquer, rubbing out, buffing and the like but not much using poly. I probably should have left the ridge alone just sanding lightly not through the finish and rubbing out but well.... to late now.  Thanks for any advice. I'm a cabinet maker, not a trained luthier but have done my fair share of guitars fixes.

[Allan Lang]

Hi Bill,  this Tokai has a very thick finish, to try to scrap it off and sand would be a task,( I believe?) I don't want to think the neck. I once bought a new off-brand strat neck with poly, I didn't like the thick finish which was poly and I tried to sand and scape it off, it wasn't happening for me, perhaps it was a conversion varnish with the hardest finish. Since it was an all maple neck, I used stripper and still after sitting on the neck for fifteen or more minutes it wasn't blistering off. I had a hell of a time with stripper getting it clean.

Maybe this Tokai neck isn't a hard poly or conversion varnish and might come off much easier like you say but I'm not confident I can do it. I know take it to someone who can.

I guess I have a decision to make...? I can always try to de-gloss the neck and clear coat lacquer, shading if needed to match. If that doesn't turn out good, then take the finish off as you suggested.

Thanks for all the good advice Bill,

Al

[Peter Laine]

why not just try clear poly.  on cars they just patch sand & buff   I'm not sure what type of paint alcohol will soften, maybe shellac. if you want to test for laquer use laquer thinner

[Hesh Breakstone]

Although not entirely on-topic here as a builder of acoustics as well I'm rethinking my own use of poly for the very same reasons brought up here.

Many of us will admit, perhaps after a few drinks only.... that sometimes when playing a poly finished guitar or any gutiar with a very thick, tenacious finish that there is at times a perception that the finish can be heard....  Now before you ask me if I have been smoking the drapes (I prefer blinds...) more specifically if it's true that french polished shellac is the very most sonically transparent finish then is this not also admitting that some finishes, thicknesses, etc. are audible and likewise perhaps undesirable?

We see lots of inexpensive guitars in for repair too and IMHO the ones with thick, poly finishes tend to sound more like finish than what ever tone woods the maker may have used.

With this conversation and my own personal experience with how difficult it is to repair a poly finish, well.... and my own impressions of the down side of poly in tone terms it's got me wondering why I would ever use the stuff again...  As such me thinks it's time to go back to lacquer and sorry for the partial high-jack too.

[Eric Steven Johansen]

Hesh, better go to smoking the drapes, my preferred method, LOL. I agree whole heartedly on the poly issue, in my opinion you might just as well wrap the whole guitar in a clear 6 mil plastic bag. French polish is #1 followed by lacquer. Gotta go, the drapes are still smoldering.

[Hesh Breakstone]

LOL - I trust that you got your drapes put out and also hope that you have a medical drape card too.... ;)

[Allan Lang]

I've read about your theory before and think it's true but highly more for an acoustic then an electric. The thinner a finish in general, the louder an acoustic top vibrates. Dan Erlewine of Stewart McDonald fame, is very big on not deadening acoustic tone and somewhat electrics with thick finishes. Lacquer's made today are much better than in the 50's and 60's. I'd never use poly on a new built finish.

[Hesh Breakstone]

Don't get me wrong poly can be a fine choice, ask Bob Taylor, but it's thickness or more specifically it's desired thinness is in my view key to not having the instrument sound like it was dipped in Plastidip....

Combined with the difficult-to-repair aspects for we mere mortals who are not in the business of spraying poly and with as you rightly said better lacquers on the market these days I'm leaning toward lacquer and have been for the last 5 or so that I built.

[Allan Lang]

Ditto.

Taylor has a nice 'thin' non-lacquer finish and their instruments sound fantastic, I own one, seems we both agree. I'm with you on the fix-ability of lacquer finished instruments vs. poly's. I once remember having a Washburn acoustic that was finished on the inside (before assembly I assume) and couldn't figure why someone would do that, seems to me to deaden tone.

Take care and thanks for sharing your knowledge,

al

[Eric Steven Johansen]

There's a school of thought that thinks finishing the inside of the box will bring climate stability to the instrument. Possibly, but I think it affects tone adversely by taking away some of the "warmth" that the bare wood imparts. Different strokes for different folks I guess.

[William F.Eden]

Well I have tryed  finishing the inside but just the sides and I beleave that it gave the Instrument

more volume.I once done a violin as well and found it did the same to it.Just my exp.You have to try things before you can realy know if it dose anything different to the Instrument. The same thing applys to weather you should scallop the braces or not. I beleave that the more freedom of air flow you can give to the inside of the Instrument the better  Bill.......... 

[Jason Gatewood]

I don't think you would devalue a Tokai if you refinished the neck, I could be wrong, so don't hang me for it... but I have done some refinishing on my Electra Super Rock, and I feel confident that no one would ever question if every bit of the finish was original.

[Todd Mylet]

Allan,

I don't think I would refinish the entire neck.  Even if you refin the neck, you'll have a blend line.  The blend line will be at the neck/body joint but it would be difficult if not impossible to get a smooth transition from body to neck (there will be a bunch of inside corners to try to sand and buff).  So I think the finish work would end up visible.  If the touch up will be visible, you may as well touch up the smallest area possible.  So I would just spot touch up the affected area.  I would do this with a combination of black Sharpie and super glue.  It may sound like the way a bona fide hack would approach this job, but I do this fairly regularly and get good results.  The repair is not invisible because the black color won't match exactly and you'll be able to see the transition line between old and new finish in the clear coats.  But it doesn't jump out at you, looks well repaired, and feels smooth to touch.  I think that's the most you can hope for.

My technique is pretty simple.  First, smooth the affected area, which it sounds like you have done.  If you have areas where wood is missing, fill it with something other than super glue (I often use epoxy putty).  Once the area is smooth and uniform, sand bare wood to 220 grit and the original finish around the repair to 600 grit.  The idea with the 600 grit is to sand a large enough area that all your touch up occurs on finish that has been scuff sanded.  Now color the area that isn't black with the Sharpie.  Next cut a bunch of strips of blue shop towel to about 1 1/2" squares.  You'll need 15 or 20 squares.  Spray one square with super glue accelerator.  Wipe the area to be finished with the accelerator.  Fold a second small towel square in four and wet the corner of it with thin super glue.  Rub the super glue quickly across the area to be finished.  You have to move quickly because the super glue flashes quickly on the paper towel and it dries quickly on the guitar (because of the accelerator).  Don't try to make a second pass with the super glue.  The glue dries almost instantly.  Take another wipe with the accelerator (you do not need to apply more accelerator to the towel, one initial spritz goes a long way).  If you need more black, and you probably do, use the Sharpie to color more in.  Allow the marker ink to dry for a few seconds then apply more super glue with a fresh shop towel square, in the same manner as the first coat.  Continue in this manner, adding color with the Sharpie between coats until it is sufficiently opaque.  This usually takes 3 to 5 coats.  Once the area is black enough, continue adding coats of super glue without adding black between coats in order to build up a thick enough layer of clear finish to sand and buff.  This usually takes 10 or 12 coats.  The entire process to this point should take around 15 minutes.  You can do a light level sanding every 5 to 7 coats just to keep things somewhat smooth and level.  When you think you have a sufficient build up of clear super glue finish, sand and buff the area as you would lacquer or poly.  I'll usually sand with 600, 800, and 1500 and then buff on the pedestal buffer.

I like this touch up technique because super glue is clear, fast, buffs nicely, and adheres to the old finish well (it's glue after all).  This technique works well on clear finishes too, although it's touch to match any ambering of the old finish.