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| Nitro over French Polish http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=10910 |
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| Author: | JJ Donohue [ Tue Feb 13, 2007 12:58 am ] |
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Has anyone ever done this? One of the 3 I recently FP'd is for my Godson as a college graduation present. I originally wanted this one to be nitro but couldn't find a suitable location to spray so I FP'd along with the other 2 I'm working on. Now that Joe has offered to help me with Nitro, I'm going to do it. I just know he needs the greater protection that nitro will provide and he won't take the care that a FP'd instrument requires. So I'm planning to sand the top back to wood and start from scratch and probably scuff sand the B&S. Has anyone ever done this and are there any issues I should be aware of. Seems pretty straightforward but just wanted to make sure. TIA |
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| Author: | Dave Rector [ Tue Feb 13, 2007 2:11 am ] |
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JJ, my understanding is that nitro adheres very well to a shellac finish. I wouldn't think you would encounter any problems at all. I'm not sure you would even need to sand all the way back to wood. I often use shellac to seal a neck before spraying nitro on it, and have never had any problems with it. Wait for the experts though. 
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| Author: | JJ Donohue [ Tue Feb 13, 2007 2:18 am ] |
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Dave...the reason I want to sand back to wood on the top is to assure that I'm only laying down a minimal thickness on the top. I don't believe that the B&S are that critical. If it were for me, I'd leave the top FP'd but it's essentially for a kid. |
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| Author: | Dave Rector [ Tue Feb 13, 2007 2:25 am ] |
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Got ya JJ. That makes perfect sense. I think I may have misread your first post. |
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| Author: | Mike Mahar [ Tue Feb 13, 2007 2:40 am ] |
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There is a rule of thumb that says Never put a hard finish over a soft finish. That is what you are proposing to do. That being said, many people put a sealer coat of shellac on before they do any other coat so a thin coat should be OK. Is a full french polish coat too thick? It might be better to sand it down alot. A half hour with a palm sander should do it. That's what I'd do. Than I'd wipe on a seal coat of shellac just to cover up the place where I sanded through. |
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| Author: | Don Williams [ Tue Feb 13, 2007 2:53 am ] |
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Hesh, I'm glad you mentioned that. If you didn't I would have! Shellac makes a great base-coat for just about anything, but is a very slick finish if not sanded. |
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| Author: | JJ Donohue [ Tue Feb 13, 2007 3:21 am ] |
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Thanks guys...looks like I'll sand off the B&S as well. Believe me...sanding this is gonna hurt, since it took such a long time to achieve what I believe is my best FP effort so far. So I really have to look at it as just another tuition cost. Does it ever end? 
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| Author: | JJ Donohue [ Tue Feb 13, 2007 7:23 am ] |
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Hesh...Freddie must have been one of those "patsy" golfers...you know, the kind that rarely collects and more often pays out at the end of a round! That can get to be expensive! This FP is VERY thin so I'm not too worried about the additional Nitro thickness. And upon further review, I'm not too sure that I need to sand all off from the B&S...after all, we apply shellac as a base for Nitro anyway. Therefore, I agree with your opinion to do light sanding before applying Nitro. I'll probably sand more thoroughly on the top just to keep the finish as thin as practical. |
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| Author: | Colin S [ Tue Feb 13, 2007 9:51 am ] |
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Why not leave the top just French polished and nitro the back and sides? Best of both worlds then. Colin |
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| Author: | burbank [ Tue Feb 13, 2007 10:12 am ] |
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Mike brings up a good point about not putting a hard finish over a soft one, which begs the question as to whether we're not doing just that by putting nitro over sanding sealer. I dunno. |
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| Author: | Alain Desforges [ Tue Feb 13, 2007 10:38 am ] |
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JJ, did you use any kind of compoung to buff your FP out? If so (ans I suspect you did) you'll definitely have to sand her down real good... I don't think nitro would stick to well to Maguires! |
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| Author: | JJ Donohue [ Tue Feb 13, 2007 10:45 am ] |
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Pat...Nitro has been going over shellac (sanding sealer) for decades on millions of guitars. I really don't see this as a problem. Colin...you're right, as usual. If it were for me I would do just that. I'm just concerned that Andrew (my Godson) would not be as careful with the guitar as he needs to be. |
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| Author: | JJ Donohue [ Tue Feb 13, 2007 10:47 am ] |
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Alain...It has been buffed out with Menzerna. I plan to clear the surfaces with Naphtha and even possibly ETOH before sanding. |
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