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.

[Ned Knepp]

Hi Allan,  The question of fixing Poly finishes keeps coming up and, if I remember correctly, no one has found anything that will melt the finish enough to blend with it. I believe most of the people that work with it here would probably strip the whole neck and refinish to get a unified finish. 

I have, as and amateur, used CA glue to close finish cracks with finish loss BUT it's always obvious that a crack was there because the patch finish isn't incorporated into the original. 

Maybe, other denizens of the forum will kick in their opinions too. 

[William F.Eden]

Ned is right the best way is to refinish the back of the neck.B.ill............

[Allan Lang]

Thanks, since this is a vintage instrument I really don't want to strip the entire back of the neck, it is a Les Paul and set neck so I'm not entirely sure I'm capable of finishing the neck as to not tell it's been refinished. I have spot blended lacquer o lacquer before with very good results. Can I use poly with a shader mixed in (alcohol base)?

I have no finish to practice on. These older Tokai's Les Pauls are becoming collectable and if this was lacquer I was dealing with I'd be able to fix it unnoticeable.

I have sprayed poly but only on the first finish with good results. Does poly blend into poly similar to lacquer to lacquer? I know once poly is cured any finish is just on top but will poly over poly stick and buff-in? I've seen a few of these Tokai's with neck breaks that were touched-up on the back like this one needs but have no idea what materials were used and the necks were poly base top coat.

What about spraying shellac over the poly after de-glossing the the touch-up and then mist coats of shaded lacquer?

[William F.Eden]

 Allan  you can spray lacquer over the poly but when you go to buff it up it will show a shadow were the two come together.Bill...........

[Allan Lang]

And probably "peel" with little effort...?

Poly over poly, rub out?

Thanks,

al

[Paul Verticchio]

Hi Allan.

NICE guitar. Tokai was making "dead on" LP reproductions a decade before Gibson did.  AND, they're much nicer than their USA counterparts.

The "vintage value" of the instrument was greatly devalued simply by the neck crack. Even refinishing the entire cracked neck will not greatly affect it's resale value. Perfect "high end' Tokai copies of Gibsons (EC++) of that vintage are selling for between $1000 & $2500 so we're not talking high value compared to other guitars in the vintage world.

Yes, I think everyone is saying "apply the poly coat & blend & buff so it feels right, BUT there will most likely always be a witness line between the original finish & the spot finish.".  It's a simple "it is what it is" situation.

If you run across this type of situation in the future, may I suggest using a scraper instead of abrasive paper to do the finish leveling. As a cabinet maker, I'm sure you're extremely skilled with scrapers.

Photo's when you're done with the job?

Best of luck in bringing this "very worthy" guitar back into playing condition,

Paul

[Allan Lang]

The glue up of the slightly cracked neck went well. I thought the finish was lacquer and when I was scraping with a razor blade and tape, I broke through the finish, again thinking it was lacquer I wasn't concerned at the time so I sanded the fixed break and as I got to the wood, the fixed crack disappeared completely. I figured I could stain and shade spray if needed. When I tested the finish, oh no it's not lacquer. I should have tested before hand but I read that these Tokai's where lacquer, only finding out "the top of the line models" were only finished in lacquer. If I could only get the finish on the break with no finish lines then it would not be noticeable.

I guess I could try to touch it up and if I "screw up" I could always refinish the whole neck's back.

What if I wet sanded the the entire back, de-glossing and giving a surface to bite with no line marks could I spray the entire back with mist coats of lacquer to start. After four or five coats I could rub it out and buff. I just know that stripping off all the old finish and poly is not an easy task and I risk more damage to the binding.

I could spray shellack for the first few light coats for a even better adhesion, then lacquer. This method sounds like no transition lines and no peeling problems. My experience is with lacquer only with great results. I never sprayed shellack but read that it can take lacquer well and sticks to de-glossed poly.

Sound like a decent fix?

Thanks for all the help guys,

al 

[William F.Eden]

Well that would be new to me as I have never had it peel off .Bill..............

[Allan Lang]

I've had water base poly peel off when slightly dented, even a cotton rag buffing a sheen to match started a peel over lacquer, once it starts you can't blend in the line, it peels if you keep at it. You are right. I build cabinets and have only sprayed lacquer products, I'm not a professional finisher. 

I appreciate all the advice here. I could try the lacquer spot fix over the poly and if I have a line I guess I could do my fix above...?

I know I should have tested the neck before I started to scrape, I would have been much more careful and accepted the mend would be visible. But live and learn.

Thanks again all,

al

[Ned Knepp]

Allen, It sounds to me like your approach is doing everything that you would do for a refinish except actually stripping the original finish f you are going to go sand the whole neck and re-coat the whole neck, why not just remove the old finish and refinish. The end product will look better and be a more sure repair.

[Allan Lang]

Probably good advice, I'm just afraid stripping the back with stripper I'd have a good chance of ruining the aged binding and also matching the original finish's exact color including the binding. The guitar is 31 years old and has an aged finish...? So I thought of "scratch sanding" the whole back for bite and then bring it back with lacquer and shading if needed.

Thanks Ned,

Al

[William F.Eden]

Allan you would not use stripper to take the finish off ,you would use a razerblade and sand paper and then ooo-steelwoll .Bill............