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Thread: Clearly I am doing something wrong - WB spraying an electric guitar

  1. #1

    Clearly I am doing something wrong - WB spraying an electric guitar

    I built a guitar 15 years ago with my dad and am now trying to refinish it. I have a Fuji Mini Mite 3 sprayer and have been using Timbermater grain filler and water-based varathane poly.


    The problem is several-fold, but first let me spell out what I’ve done so far:


    1) I sanded down the original finish and added some contours to the body. Sanded everything up to 220


    2) I grain-filled, let it dry, then re-sanded to 220


    3) I sprayed 7 light coats over a few days of the WB poly, and then screwed up the last coat with an overly open sprayer that created drips. Decided to start from scratch and sanded back down to the bare wood (at least I thought I did).


    4) After sanded it back down I reapplied grain-filler. Where I am now is I’ve just used the orbital sander with 220 to knock off the dried grain filler. This is where the issues start to multiply.


    4a) the first issue I noticed was that using 220 sandpaper by hand would create tiny scratches, but I can’t use the orbital on some of those inner profiles. So how do I get this smooth without using the orbital? Higher grit sandpaper? My understanding is that going above 220 could prevent the sprayed finish from adhering properly.


    4b) To get the rest of the dried grain filler off without the sander, I tried another method I saw recommended here which was to simply wipe everything down with a wet rag. That worked for removing the excess grain filler but revealed another problem of extreme splotchiness rewulting from some earlier error (see attached photos). Perhaps this is finish from those 7 coats that didn’t get sanded off? I don’t know.


    As of now I see two things that I think are going on which are highlighted in the attached photos. In photos 1 and 2 you can see the splotchiness that I think is simply finish that wasn’t sanded fully down to the bare wood. In photos 3 you can see a closeup of that splotchiness (bottom half is darker) and in this view the lighter part actually has some open pores. So maybe the sanding took out some of the grain filler? So is the problem that I’ve knocked out the grain filler or that I didn’t sand off the finish or both? And what is the best way to resolve?


    Any guidance on a next step is much appreciated.
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  2. #2
    Join Date
    Sep 2006
    Location
    Deep South
    Posts
    3,970
    I do not agree that sanding past 220 grit will prevent adherence to the wood. I will say that sanding to 400 grit does not improve things unless you are trying to get rid of scratch and swirl marks (like you are). After the first coat, you are sanding finish instead of wood.

  3. #3
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,648
    Oh boy, that's not good. If I were you I'd get a chemical stripper and strip any remaining finish off, then wipe/wash off any TimberMate that might still by in the pores. If you were able to sand it w/o scratches before you initially started the finishing process you should be able to do so again once it's back to raw wood. Assuming that's correct I would start by applying a sealer coat of Sealcoat shellac, then apply the grain filler. That way, if you screw up you should be able to wipe off any excess grain filler w/o shadow marks. After the grain is filled, and it may take more than one coat, then I would spray another light coat of Sealcoat, and then your topcoats.

    About your topcoats; seven coats is at least 3 too many. There should be no reason for more than 2 or 3 coats at 3 - 5 wet mils each, 4 max. Normally, you want to spray those coats as soon as possible, too, not spread out over a few days. With many finishes you scuff sand after an hour or two and respray, repeat until done. If you wait longer than X hours (24 being typical) you MUST sand enough to give the finish something to bite into. So it's better to apply all the coats as soon as the drying allows so the layers will bond better.

    I hope that helps.

    John

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