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Having trouble finishing koa
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13316		 Page 1 of 1
Author:  James Orr [ Tue Aug 21, 2007 10:43 am ]
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I have a highly figured board from Volcano for the baffle of an amp head,
ebony faceplate, cream chickenhead knobs. Theoretically it will look
gorgeous with black tolex.

After sanding to 400, I've tried finishing the koa with Maloof's poly/oil,
lost half the flame, and just buffed out some nitro and also lost half the
figure. After finishing with the nitro I realized it probably wasn't a good
move anyway, given all the heating up and cooling down that it's going to
experience.

How the heck can I finish this board in a way that brings OUT the figure
instead of minimizing it? Here's the board after I brushed on some
shellac just to see to color and flame.

Author:  jfrench [ Tue Aug 21, 2007 10:48 am ]
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French polish it.

Really.
Author:  James Ringelspaugh [ Tue Aug 21, 2007 10:52 am ]
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I think you answered your own question with the picture. How about a seal coat of shellac to bring out the curl?

I might try epoxy as well.
Author:  Don Williams [ Tue Aug 21, 2007 10:52 am ]
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Or, shoot vinyl sealer before shooting lacquer. Or shoot shellac before shooting lacquer. Or, epoxy fill, wash coat with epoxy, and shoot with a poly of some kind. OR get some of that really thick epoxy coating stuff and bury a dime in there too.

The secret is to spray (brush/wipe) on something that has the ability to "wet" the wood, such as shellac, vinyl sealer, or epoxy.
Author:  Jim Watts [ Tue Aug 21, 2007 10:53 am ]
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or just brush on some shellac. Looks great!
Author:  James Orr [ Tue Aug 21, 2007 11:11 am ]
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Ok, thanks all.
Author:  TonyFrancis [ Tue Aug 21, 2007 12:21 pm ]
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I build everything out of koa...and have found the two best methods really are either shellac or shellac with a top coat of nitro.


Spraying maybe a 1  1/2 cut  of shellac is pretty easy, or french polish if you have the time. These are the two most traditional finishies for all koa instruments, and look killer...bringing out the figure on even the most average peices. Sanding to 400 wont help..220 is fine or 320 if you can see any marks. I also like to fill with shellac/pumice on these higer figure peices.


Good luck!
Author:  KenH [ Tue Aug 21, 2007 12:34 pm ]
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Hesh, does the west systems have any color to it? I love the way z-poxy fills the pores, but the dark color it adds is sometimes too much for me. I would love to find a clear substitute for it.
Author:  James Ringelspaugh [ Tue Aug 21, 2007 2:15 pm ]
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[QUOTE=Hodges_Guitars] Hesh, does the west systems have any color to it? I love the way z-poxy fills the pores, but the dark color it adds is sometimes too much for me. I would love to find a clear substitute for it.[/QUOTE]

I'm not Hesh, but I have worked with System 3 epoxy and my experience is that like any other epoxy it darkens, or makes the wood look 'wet'. If you don't like that effect you'll need to sand it back to bare wood after filling pores.
Author:  James Orr [ Tue Aug 21, 2007 2:39 pm ]
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Tony, sanding to 400 was because I was intending to work with oil.

I stripped what I had and did the initial coat of Z-Poxy. I did some testing
last fall, brushing shellac on an area, Z on an area, and Z on top of shellac
on an area, and preferred Z.
Author:  Rick Turner [ Tue Aug 21, 2007 3:24 pm ]
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West Systems epoxies are "water white"...which is paint maker talk for clear as water.   Great stuff.   

To pop figure you could also do a light stain with MEK or aniline brown dyes and then sand back. Then epoxy or use Waterlox, let that dry completely and go from there.
Author:  TonyFrancis [ Tue Aug 21, 2007 10:41 pm ]
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I used to use Zpoxy...but found the pores always went "black" when using it. The slurry made from shellac and pumice works real nice as a true clear filler and looks very natural.


Rick Turner is right on about the dyes...they can also be used to good efffect if you arent in the habbit of sanding though the finish!


Does anyone know how those epoxies colour over time and or sunlight?


 
Author:  JohnAbercrombie [ Wed Aug 22, 2007 10:31 am ]
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One point about WEST (and other brands as well) is that the amine? hardeners can react chemically with some woods and change the color.
I've used many gallons of WEST (on boats, not guitars) and color changes are not that common, but it's always a good idea to do a quick test on some scrap.
I wish I'd known about epoxy pore filling when I built my koa guitar in 1981. I used a silex-type oil based filler (dark) and it really emphasized the pores (duh!) at the expense of the rest of the figure.

Cheers

John
Author:  Michael Dale Payne [ Wed Aug 22, 2007 12:06 pm ]
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I have never had Zpoxy go black on any wood I find that strange as Zpoxy will cure to a very fain amber tint but unless something impregnates the epoxy like a dark saw dust it will not darken.
Author:  James Orr [ Wed Aug 22, 2007 2:01 pm ]
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Man, the Z-Poxy definitely did the trick. I'll post pics when the entire
head is finished just so I don't have a million threads floating around. If I
can drill these last two holes through the ebony (that I've already had to
nurse back together with CA), I'll be a VERY happy person and this will be
a VERY attractive amp.       
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