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| Zpoxy sand through http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=3270 |
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| Author: | Terry Stowell [ Tue Sep 20, 2005 4:36 am ] |
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Can't seem to beat to death the zpoxy questions on this forum... I've applied and sanded more zpoxy coats than I care to count. It *appears* that I'm sanding throught to wood, as the white powder gathers in spots,the more I sand the larger they get. I put a dab of water on to see if it gets dark (as wood does, until it's dry). It doesn't seem to be wetting the wood. I though maybe I'm just going through layers.... It acts like it's still sealed, and I'm not mostly not getting sawdust on the paper. Confusing. I'm tempted to GETNLY sand the whole thing back until the whole guitar "powders" up and seal it with shellac. Then KTM-9 it. QUESTION: if I shellac seal the entire guitar with the current *apparent* sand throughs, will there be witness lines in the (KTM-9) finish? I've tried applying with stiff and flexy credit card (which leaved a decent film) and also used squeegeed it off (leaves little behind, but smoother) This is my first time using the zpoxy method. Any help is appreciated |
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| Author: | John How [ Tue Sep 20, 2005 4:53 am ] |
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The final coat of epoxy should only need a very light sanding if it is flat. If your having trouble getting it flat without sanding thru, you might consider wiping on a thin coat of z-poxy thinned 50% with some denatured alcohol or better yet everclear. Put it on with a lint free cloth and all you'll need is a very light sanding so the KTM-9 has a little rough to bite into. |
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| Author: | LanceK [ Tue Sep 20, 2005 4:53 am ] |
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Terry, what I do after applying the zpoxy is sand it all the way back to wood, remove it all! Then check and see if the pours are full, chances are you have filled your pours 
Now, make a batch of 50/50 zpox and denatured alcohol, mix it real good and using a wadded up piece of old teeshirt, whip it on in long straight motions from one end to the other, only overlapping enough to ensure full coverage. after is dry, a quick scuffing with 400 grit and your ready for finish. Hope this helps. |
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| Author: | Michael Dale Payne [ Tue Sep 20, 2005 4:55 am ] |
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Ther is nothing wrong with sanding back just to the wood. But I got to say that it is very noticable when you sand through. Very simular to sanding throug any finish. Keep in mind the intent here is to seal the pores. Just be sure to sand equal every where. I myself perfer to leave a fine film. It really pops the wood color. However if you sand just back to the wood and leave the epoxy in the pores, you have done the main job. I seal with shellac either way. |
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| Author: | John Kinnaird [ Tue Sep 20, 2005 5:20 am ] |
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Lance Do you spray nitro over the zpoxy, or are you using KTM-9 |
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| Author: | LanceK [ Tue Sep 20, 2005 5:27 am ] |
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John, I have done KTM-9 but Tony is doing my finishing now and he is using Urethane, over either system 3 if he does the pour filling, or z-poxy if I do. Both work fine. |
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| Author: | Michael Dale Payne [ Tue Sep 20, 2005 8:37 am ] |
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Terry, After reading your post again I noticed you said the dust was gathering in spots and that the more you sand the larger the spots get. This sounds to me as if you have an uneven film of epoxy applied or void valleys. This would cause the dust to gather in these valleys and the size of the valleys will increase till you sand down to the level of the valley floor (lack of better term) If this is the case the voids were formed either by air pockets in the epoxy when applied or an un-level edge in you application squeegee or fold over caused by working beyond workable pot life. This is the reason I don't use the adhesive 5 min or 20 min Zpoxy but rather the Zpoxy Finishing Resin. It has a much lower viscosity than the epoxy and longer workable pot life. If this is the case I would sand back to the wood but no more, over the entire piece the re-apply with a good squeegee. I could be reading something into what you are saying that you don’t mean though. |
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| Author: | Terry Stowell [ Tue Sep 20, 2005 8:53 am ] |
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Good points. My spot aren't collecions of air bubbles, but rather look like sandin through. I think I am just over sanding a bit, trying to attain a smooth, even surface. One more try (thinned down) and I'm not gonna be as particular. |
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| Author: | Paul Schulte [ Tue Sep 20, 2005 9:03 am ] |
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Those "dust gathering points" sound like you are getting down to bare wood alright, I've seen it before myself. You may be leaving small dips and mounds over the surface of the guitar and the expoxy will fill in dips but the mounds remain high and sand down to bare wood easily. My solution is to take extra care in the final sanding of the guitar to get all surfaces even. This little extra time has saved me hours of fussing later on. I leave a thin smooth coat of epoxy over the entire surface when I'm done. |
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| Author: | JJ Donohue [ Tue Sep 20, 2005 9:17 am ] |
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Every time I've used Z-Poxy (3 times) and level it I actually feel the surface with a fingernail. It feels radically different than bare wood. It's been the only way I can distinguish between sanding through and not sanding through. |
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| Author: | Colin S [ Tue Sep 20, 2005 7:54 pm ] |
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When I pore fill with Z-Poxy, that is exactly what I like to do - Pore Fill. For me the idea of the Z-poxy is to fill the pores, not to act as a sealer, so when I sand back, and it shouldn't take too much sanding if my squeegeying has been done properly, just the pores have z-poxy in them the rest is back to bare wood. Then, go to it with your normally finish sequence, for me that's French polishing. Colin |
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| Author: | Arnt Rian [ Tue Sep 20, 2005 8:29 pm ] |
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I'm with Colin here, I want the epoxy (Araldite) only to fill the pores so I sand back to bare wood until I have a non porous, even surface. My rationale is that I have better control over the final finish thickness this way and I have a good surface for the finish to adhere to. I then spray nitro. |
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| Author: | Dave Rector [ Wed Sep 21, 2005 12:14 am ] |
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I'm with Colin and Arnt on this one. I sand all the way back to the wood leaving epoxy only in the pores. Then I usually spray a coat of sanding sealer just to make sure I didn't miss any small pores, then on to the Mcfaddens. |
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