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| Different finishes for body and soundboard http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=54213 |
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| Author: | bcombs510 [ Sun Jun 20, 2021 4:20 pm ] |
| Post subject: | Different finishes for body and soundboard |
Hello, I’m nearing the finish line (haha) and was thinking about trying a French polish top with a sprayed UV cured poly for the body and neck. I’m thinking of mocking up a body to have some practice but wondering if anyone has done this already and might have some pointers? I’m specifically interested in the masking off of the top. Is it useful or should I just sand back any over spray that happens to get on it? Any other tips considering the top will be French polish? I’ll need to fill the rosette as usual and I’m thinking mask off the bridge and fretboard extension with frisked film. Just curious if others have blazed this trail already and can share learnings (for or against). Hope you are all well. Happy Father’s Day! Brad Sent from my iPhone using Tapatalk Pro |
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| Author: | Ernie Kleinman [ Sun Jun 20, 2021 7:56 pm ] |
| Post subject: | Re: Different finishes for body and soundboard |
Brad, there are many ways to FP a top. There are a number of youtubers who show an tell, les stansell an michael thames are 2 that I remember.My suggestion would be to get a piece of top wood and practice your FP technique , before you take the piunge. My technique is to initially brush on 2 coats of # 2 cut shellac, dry 24 hrs, and sand to 400 and, the next day begin the FP process ,Jeff jewitt has a book on finishing , that includes a section on FP there are other authors out there as well. There is also mr flexner , who writes about finishing. I prefer a slower finish schedule for the rest of the instrument with varnish or lacquer. or polyurethane , Cant help with the uv cured poly.I would suggest taking your time doing the fp. It takes quite a bit of learning, to get the proper technique down to your satisfaction. Shellac is also very sensitive to temp and humidity . I try to aim for at least 65 deg and 45% humidity. Best of luck ! |
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| Author: | Clay S. [ Mon Jun 21, 2021 10:34 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
I would mask off the top before spraying poly. It might save you from removing more of the soft spruce than you want to, than if you had to sand off overspray. It could also allow you to band in the top of the binding and coat that with the tougher polyester finish. |
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| Author: | John Arnold [ Mon Jun 21, 2021 11:58 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
Definitely mask off the top. It is a simple job, particularly if you use 1/4" wide masking tape to do the curves. Sent from my SM-G950U1 using Tapatalk |
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| Author: | Toonces [ Mon Jun 21, 2021 12:35 pm ] |
| Post subject: | Re: Different finishes for body and soundboard |
I've done this a few times. Definitely mask off the top and then spray. One thing that is helpful is to round over your bindings -- this will make it easier to "blend" the two finishes together at the binding line. French Polish is very delicate but it will ensure you aren't negatively affecting the tone of the guitar. You can get similar results with lacquer or urethane (not with polyester tho') but the finish must be exceptionally thin (under 3mils everywhere on the top) and that is very challenging. If you can, use Everclear alcohol instead of denatured - the methanol in denatured is not good to get on your skin. |
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| Author: | jfmckenna [ Mon Jun 21, 2021 1:14 pm ] |
| Post subject: | Re: Different finishes for body and soundboard |
When I FP I don't mask off the bridge preferring to just scrape it off with a sharp rolled over chisel. I do mask the FB extension but that is because the masked area is much smaller than the footprint. Taping the bridge tends to leave a bit of a ridge right at the edge of the tape. You could, and I did, of course make that footprint smaller too. But I find FP very easy to scrape back to wood. |
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| Author: | doncaparker [ Mon Jun 21, 2021 1:47 pm ] |
| Post subject: | Re: Different finishes for body and soundboard |
Brad-- Following up on Toonce's suggestion, I use Everclear instead of denatured alcohol, and it makes a WORLD of difference in terms of how pleasant it is to work with. That's my experience, anyway. You can buy it right across the river in Kentucky. That's where I get mine. Following up on JF's suggestion, I also don't mask the bridge area when applying French polish. You can, but I personally find it easier to just scrape off the finish. There shouldn't be a lot there to begin with. |
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| Author: | SteveSmith [ Mon Jun 21, 2021 2:24 pm ] |
| Post subject: | Re: Different finishes for body and soundboard |
I like masking the bridge and the fretboard extension when I FP the top but I use Frisket Film. I've done it both ways, it's not a big deal. If I have to mask off the top I use the 1/4" 3M 233 to go around the curves and then use the 3/4" tape to tape a rough cut piece of freezer paper to the 1/4" tape (I just happen to keep freezer paper around). |
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| Author: | bcombs510 [ Sat Jul 03, 2021 10:46 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
Thanks all, this is very helpful. I’ll post some results. Simon, I worry about bringing the UV cured poly up onto the top for the binding because of the film thickness. I could sand it and blend it to zero and then FP the top but I wonder if there will be a bump up that could be felt when running fingers across it? Thanks all! Brad Sent from my iPhone using Tapatalk Pro |
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| Author: | Hesh [ Sat Jul 03, 2021 10:51 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
Yep that was the word when I was building, FP top, Cat poly back and sides, tough and responsive. |
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| Author: | Toonces [ Mon Jul 05, 2021 12:22 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
Hi Brad, I don't think you need to worry about there being a bump at the intersection between the two finishes. Let the poly build up nicely on the binding -- then after you remove the mask from the top just smooth over the binding with 400 grit. Try to reestablish a nice roundover -- and the scratch pattern left from the sanding won't extend that far - don't sand beyond the roundover. The French Polish can then be built up over the binding and used to fill the scratch pattern on the binding until it is glossy again. As long as you keep the finish intersection at the binding, it should be mostly invisible because of the curve. As Hesh stated, a good durable finish on the back/sides/neck with a French Polished top is one of the best ways to build a guitar. I don't do this because it is more time intensive and because I can keep the urethane ultra thin on the top. I think most folks will really struggle a bit with getting a finish as thin as is ideal (0.003" max) -- and that's why French Polish is so great. You guarantee that you aren't limiting the potential of your guitar. Good Luck !!! |
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| Author: | bcombs510 [ Mon Jul 05, 2021 8:49 am ] |
| Post subject: | Re: Different finishes for body and soundboard |
Thanks, Simon! I will give it a shot. Sent from my iPhone using Tapatalk Pro |
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