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| Finish Input http://luthiersforum.com/forum/viewtopic.php?f=10101&t=28939 |
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| Author: | Nate Swanger [ Mon Sep 06, 2010 7:06 pm ] |
| Post subject: | Finish Input |
Need some help making a decision (again), I've put off deciding on what to do about finishing my first and now its about time. First, let me tell you what i was thinking about doing, and then give me some feedback or drawbacks and if you have done classicals/steel strings this way before. Then maybe some suggestions. What i was thinking about was doing a French polish on the top and then having a friend who has the equipment (he sprayed his first Martin kit a few months ago and it turned out well) spray nitro on the rest. I would give the whole thing a spit coat or two of shellac first so that every thing matches and so i can poor fill with pumice. I was just thinking the nitro would be nice to help prevent wear and tear on the back as this would become my every day guitar it will get used quite a bit. Any way some of the specific questions I also had was which first? spit coat it all, but then should i FP first? or mask and spray first? what about the sections where they come together? Also, I still need to complete my bridge, The book im using to guide me has the bridge placed and glued before he rubs on his shellac. since im going to go a different route on the finish i wanted to see what you guys do when you finish yours with FP. Do you put the bridge on first and finish it as well or do some sort of masking (probably addressed in one of the many FP toots that i will read in more detail as the time comes) and cutting of the finish? look forward to all the great replys, Nate S. |
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| Author: | JohnAbercrombie [ Mon Sep 06, 2010 10:13 pm ] |
| Post subject: | Re: Finish Input |
Nate- I've done the nitro b+s and FP top 'thing' on a couple of guitars; it works fine, though getting a good transition at the 'corner' takes a bit of care. Now I use FP (perhaps U-beaut in the future on b+s?) on the whole guitar- I don't like to wait for nitro to harden up. As far as masking the bridge area, I don't do that as I found it was more trouble than it was worth. It's pretty easy to scribe around the bridge (I use a sewing needle in a wood handle) and scrape down to the wood before gluing the bridge. But there are lots of different ways of doing this-as I'm confident the other responses will show! Cheers John |
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| Author: | Michael Smith [ Mon Sep 06, 2010 11:30 pm ] |
| Post subject: | Re: Finish Input |
I have been having problems getting a near perfect french polish on tops. The back and sides seem to turn out great. The flaws show way more on the top. So what I am saying is it seems to be harder to get a near perfect french polish on the light colored surface of the top. also the french polish provides almost zero protection from pressure dings. If you are going to have your buddy shoot the back and sides why not the top as well? |
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| Author: | Alain Desforges [ Tue Sep 07, 2010 8:35 am ] |
| Post subject: | |
I've never done a FP/Nitro hybrid, but I've done them both seperately. I wouldn't spit coat the top before attempting FP for the simple reason that polishing the guitar this way has you built up you finish with ultra thin layers of shellac. If you go dumping a heavy spit coat with a gun you might have a hard time building up a shine in the polish afterwards without reverting to level sanding. I might be wrong, but it seem counter intuitive to do it this way. Maybe someone with more experience can chime in here. I tape off the bridge. I like knowing that the surfaces I sanded on the top of the guitar and the bottom of the bridge are the same once I glue them together and that no extra sanding/scraping/scuffing has compromised the mating area. Use a wide piece of painters tape (get the widest green one you can find) and fasten where the bridge will be. Position the bridge carefuly, clamp it down, double/tripe/quadruple check your position (Hey, I'm compulsive...). Once you're happy with that, very gently cut around the bridge with your sharpest exacto knife, making sure to angle the knife so that the cutting edge is going slightly under the bridge. You don't want to be cutting into the wood. Ideally, you'll just very lightly score the top. I use the Stew-Mac deep C clamps for this so it's relatively easy keeping the bridge in place and cutting around it. With the bridge still in palce I start removing the excess tape around the bridge. Usually, I'll have to cut a bit here and there where I didn't go through the tape with the knife. Once you've removed all the tape, and you remove the clamps and bridge, you should be left with a perfect tape outline of your bridge that is a few thousanths shy of the actual bridge size. It's actually quite easy and very quick to do, once you get past the trepidation of taking a sharp knife to your top! Ha! I can do it now in under 10 minutes. If you're FP'ing, you can very gently remove the tape, peeling it at a sharp angle against the lines. In other words, try to twist it so that the outer edge comes back towards the middle of the bridge (think 45 angle). Shellac is thin enough that you won't need to score the finish around the tape before removing it. If you're shooting nitro, it is imperative that you cut out the finish around the tape before removing it. If you don't, you'll be breaking off chips that will vary and size according to your luck and patience. Start with very light pressure. I use a ruler and the bridge itself, depending if you have curves or not. Good luck. |
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| Author: | Nate Swanger [ Tue Sep 07, 2010 12:12 pm ] |
| Post subject: | Re: Finish Input |
Some good points. For reference its a Classical built from Cumpiano/Natlson book. Also what i was thinking about doing, after further examination is similar to Bogdanovich's book. He appears to just FP the top after brushing on a few coats of shellac to the rest of the guitar. Then takes it outside and sprays the back and sides and neck with nitro. Though there isn't much mentioned about how the two merge. perhaps I'm missing some detail that is common knowledge to those with more experience with finish, but if the shellac is dried when you spray nitro shouldn't there be something similar in appearance to a glue line? or does the thinner in the nitro allow to two to blend? Filippo, I like your method but i was set on trying to pumice poor fill as that's what i have to work with, so to some degree ill have to lay down a coat of shellac on it all, would your method still work after this poor filling? Thanks guys, |
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| Author: | JohnAbercrombie [ Tue Sep 07, 2010 12:38 pm ] |
| Post subject: | Re: Finish Input |
Nate- If the guitar is for your own use, and if you don't have a 'body chemistry' that dissolves finishes, why not just FP the whole thing? It 'fits' with the classical handmade tradition, and -in my limited experience- is less hassle than spraying nitro. That said, lots of very good builders do the FP top nitro b+s combo. Here, you have somebody else to shoot the nitro, which is a big advantage. And if you are pore filling with pumice, and discover a few 'pits' after you get going on the FP, it's pretty easy to fix the problem. For nitro, I used epoxy for pore filling, which is a whole 'other thing'. Cheers John |
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