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Switching To A Poly U Finish On Next Guitar...any Tips?


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The last four guitars I've refinished /finished have been done with Nitro lacquer, and I've had pretty good results. I used behlen nitro and sprayed through a DeVillbis Finishline III gun with a medium sized compressor. My latest project is almost finished - a flat top Dean Cadillac copy (slightly larger than a Dean) with a neck made for me by Doug Darling at Soulmate Guitars. A little final polishing on the lacquer and wiring left before I call it done. It looks pretty good so far. My biggest mistake was not grain filling the Black Limba body back before staining and finishing; so it took a LOT of nitro to get it level. I did not even lift the grain with water and sand back before staining either (Colortone w/alcohol), so that could have been part of the problem. Anyway, its almost a done deal. Live and learn!

However, I've been tempted to go for a polyurethane finish on my current project; an Eric Clapton cut Explorer - one piece mahogany back from Kalamazoo (1980) with a 1/4" curly maple flat top and black Limba neck with a couple of hard maple stripes for stiffness. I've read Jeremy's (LGM) tutorial and I'm convinced that I would probably really like a Poyurethane finish because of its ease in working, durability, stability and lack of shrinking, and still giving a deep gloss. I used to be afraid of poly u because I thought it made guitars sound "dull". But I've read enough now that I think the key with any finish is simply not to get it too thick, and then it will sound fine.

First, Jeremy said that he prefers to use a "gravity feed" gun, and not a HVLP. I am confused by this because I believe my DeVillbis Finishline III is both!...gravity feed and HVLP. What am I missing here?

Secondly, I plan to use a two part automotive type poly u, as he and others recommend. What type of prep, if any, should I use between the transparant dye and spraying the poly u clear finish?

Thirdly, Jeremy recommends multiple coats, then sanding to 800 grit, then spraying 3 more wet coats within 36 hours, then sanding up to about 3600 micro mesh, then two more wet soats, then micro mesh to 12,000, then buffing! Dave at McNaught Guitars told me that when he uses poly u, he just sprays on about 6 coats, waits until the next day, then sprays about 6 more coats, waits 24 to 36 hours, then sands to about 1000 to 1200 grit, and then polishes with a buffer. Noticing a pretty big difference between these two methods, I'm wondering what MY method should be. Any thoughts on this?

Last question: I've never used a respirator mask when spraying nitro in my garage or outdoor storage closet, and have only experienced minimal permanent brain da...dam...dam...dammmmage. Jeremy says that poly u is DEADLY and that you MUST use one. So; how much will I have to spend on one that will be adequate and where is the best place to get one?

Thanks for any comments.

Edited by Stolysmaster
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The last four guitars I've refinished /finished have been done with Nitro lacquer, and I've had pretty good results. I used behlen nitro and sprayed through a DeVillbis Finishline III gun with a medium sized compressor. My latest project is almost finished - a flat top Dean Cadillac copy (slightly larger than a Dean) with a neck made for me by Doug Darling at Soulmate Guitars. A little final polishing on the lacquer and wiring left before I call it done. It looks pretty good so far. My biggest mistake was not grain filling the Black Limba body back before staining and finishing; so it took a LOT of nitro to get it level. I did not even lift the grain with water and sand back before staining either (Colortone w/alcohol), so that could have been part of the problem. Anyway, its almost a done deal. Live and learn!

However, I've been tempted to go for a polyurethane finish on my current project; an Eric Clapton cut Explorer - one piece mahogany back from Kalamazoo (1980) with a 1/4" curly maple flat top and black Limba neck with a couple of hard maple stripes for stiffness. I've read Jeremy's (LGM) tutorial and I'm convinced that I would probably really like a Poyurethane finish because of its ease in working, durability, stability and lack of shrinking, and still giving a deep gloss. I used to be afraid of poly u because I thought it made guitars sound "dull". But I've read enough now that I think the key with any finish is simply not to get it too thick, and then it will sound fine.

First, Jeremy said that he prefers to use a "gravity feed" gun, and not a HVLP. I am confused by this because I believe my DeVillbis Finishline III is both!...gravity feed and HVLP. What am I missing here?

Secondly, I plan to use a two part automotive type poly u, as he and others recommend. What type of prep, if any, should I use between the transparant dye and spraying the poly u clear finish?

Thirdly, Jeremy recommends multiple coats, then sanding to 800 grit, then spraying 3 more wet coats within 36 hours, then sanding up to about 3600 micro mesh, then two more wet soats, then micro mesh to 12,000, then buffing! Dave at McNaught Guitars told me that when he uses poly u, he just sprays on about 6 coats, waits until the next day, then sprays about 6 more coats, waits 24 to 36 hours, then sands to about 1000 to 1200 grit, and then polishes with a buffer. Noticing a pretty big difference between these two methods, I'm wondering what MY method should be. Any thoughts on this?

Last question: I've never used a respirator mask when spraying nitro in my garage or outdoor storage closet, and have only experienced minimal permanent brain da...dam...dam...dammmmage. Jeremy says that poly u is DEADLY and that you MUST use one. So; how much will I have to spend on one that will be adequate and where is the best place to get one?

Thanks for any comments.

I just realized that this post should be on the finishing "chat" area, so I will repost it there. I'm sure the moderator will erase it from here!

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  • 3 weeks later...

Well, this post is a few weeks old and no replies yet, so I'll just pitch my 2cent. I Think a nitroC finish is almost acceptable, but I've never seen (or more importantly felt) a good PU finish yet. I say almost acceptable, because in my last few builds I've used either a home brewed long oil varnish similar to a violin, or french polish, which both feel far better than Nitro or PU. It's also likely that a long oil varnish will outlast any other kind, but if Nitro or PU are in the same category of durability, it will take a few hundred years to find out. I recently saw a beautiful Schecter bass with a perfect chunk of quilted maple on the front that was ruined by a crappy (factory) PU finish. The PU was all powdery and scratched by belt buckles on the back, a real mess. My long oil varnish, by comparison, is barely possible to scratch. Its not that hard, its just tough as hell, and a sharp object just 'squeaks' along the surface, depressing it but not cutting into it. The best feeling neck I've played was finished with nothing but tung oil. Glossy nitro necks grip my palm too much and I can't play fast. I really don't have any experience with applying Nitro, and I don't mind those finishes much (except on the neck), so I'm not trying to discourage you there, but I'm pretty firmly against PU. I home brewed my long oil, but good quality marine spar varnish is very similar and can be polished to an amazing sheen that, to my eyes, beats Nitro.

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