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| Shellac/Epoxy Finish question http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=10696 |
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| Author: | LarryH [ Fri Feb 02, 2007 2:30 am ] |
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I am getting close to routing for my binding on a redwood top and want to seal the edges with shellac to perhaps help prevent some tear out. I will seal, of course, after doing any thinning along the edges of the top I feel necessary. So let's say now I have my bindings routed but I also have a strip of shellac that's laying along the edge of the top. Another factor is I love the way a thin coat of epoxy can really make the grain pop but I'll have to sand down the edges of the top and the binding to get rid of the shellac to apply epoxy. Question: should I just coat the whole top with shellac and forget the epoxy? Should route a little deeper and figure on sanding down a bit more top after binding to achieve final top thickness at the edges? None of the above? Thanks |
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| Author: | Dave White [ Fri Feb 02, 2007 2:46 am ] |
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Larry, Once you have glued the bindings in you are going to have to scrape them down for a flush fit and clear up any glue residue. In doing this you will also have to do your final top sanding through the various grits ready for finishing - as with the rest of the guitar. The shellac sealer coat is thin and should be removed in this process. Then you can decide what and in what order you want to use to finish the guitar. |
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| Author: | JWarwick [ Fri Feb 02, 2007 3:03 am ] |
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Hi Larry, What Dave said. Also, I've recently been using a thinned mix of Zpoxy in place of shellac as a general sealer. Once the box is together, I seal the whole thing. One note about Zpoxy as a sealer ... it takes much longer to dry. I seal at the end of the day and route the following AM. |
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| Author: | JohnAbercrombie [ Fri Feb 02, 2007 3:06 am ] |
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Epoxy does penetrate into the wood and alter its properties, and it penetrates into softwoods more deeply than into hardwoods. I'd keep epoxy away from the soundboard for 'acoustic' reasons. It also will tend to give uneven color to most tops. And, since most folks are using epoxy for pore filling (and the spruce/cedar family of woods don't have visible pores) there's no need for putting it on the top. Shellac is the traditional sealer for tops and most (not all-check) finishes will stick to it. After using epoxy in boatbuilding for its ability to penetrate into wood, I always have to chuckle when I see people paying $$$ for exotic hardwoods (because of their acoustic properties?) and then impregnating that wood with epoxy. Cheers John |
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| Author: | Dave White [ Fri Feb 02, 2007 3:22 am ] |
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[QUOTE=JohnAbercrombie] Epoxy does penetrate into the wood and alter its properties, and it penetrates into softwoods more deeply than into hardwoods. I'd keep epoxy away from the soundboard for 'acoustic' reasons. It also will tend to give uneven color to most tops. And, since most folks are using epoxy for pore filling (and the spruce/cedar family of woods don't have visible pores) there's no need for putting it on the top. Shellac is the traditional sealer for tops and most (not all-check) finishes will stick to it. After using epoxy in boatbuilding for its ability to penetrate into wood, I always have to chuckle when I see people paying $$$ for exotic hardwoods (because of their acoustic properties?) and then impregnating that wood with epoxy. Cheers John [/QUOTE] John, All finishes penetrate the wood to some degree or they wouldn't stay on. I think the key is what the "tonal" properties of the new wood/finish combination is in terms of damping etc. Based on the last 6 or so instruments I have done using Z-poxy I am beginning to think that Z-poxy plus the pre-cat laquer I am using does some really nice things tonally, and on my Weissenborn copy the Sapele top had Z-poxy plus lacquer on it as well and I like what I hear. It probably needs someone like Al Carruth to do some more scientific testing. I agree with you though on being cautious about putting it on a softwood top - I would do this first on an "experimental" guitar and test the effect on both tone and colour rather than first time on a "proper" guitar. |
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| Author: | stan thomison [ Fri Feb 02, 2007 4:15 am ] |
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agree here with John. I wouldn't use the epoxy on the soundboard. I don't see a reason because there really isn't a good reason to do so to pore fill the top. Maybe if using koa or something, but not cedar or spruce. The shellac and french polish will do what it needs to. If your binding is a little proud of the top a mm or so, all the shellac will come of using 220 or 320 when doing the leveling of things. |
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| Author: | JWarwick [ Fri Feb 02, 2007 4:26 am ] |
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[QUOTE=JohnAbercrombie] Epoxy does penetrate into the wood and alter its properties, and it penetrates into softwoods more deeply than into hardwoods. I'd keep epoxy away from the soundboard for 'acoustic' reasons. It also will tend to give uneven color to most tops. [/QUOTE] I understand the concern. But after routing the binding channels, I see no deeper penetration through the top x-section than with shellac. I think the key here is "thinned" epoxy. I mix it 60/40 alcohol-Zpoxy, and pad it on. It leaves a very thin coat, mostly on the surface. I've also had no problems with uneven color on redwood or various spruces. I have seen some blotchiness on WRC, and continue to use shellac on these tops. |
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| Author: | LarryH [ Fri Feb 02, 2007 8:19 am ] |
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SOOO very helpful you guys!! It gives me a couple of options and directions to go which is the best I could hope for. I'll probably use the shellac to first coat and protect then will decide later about the epoxy as a first coat for the top. Thanks so much Larry |
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