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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Repair still shows under primer

Discussion in 'Finely Finished' started by papaschtroumpf, Jul 15, 2017.

  1. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    I'm modifying an Epiphone LP Jr for Tele style bridge and controls. (Making a Fano SP6 inspired build).
    I chose this project because I wanted to see if I could fill holes in the body and redrill/route for the new configuration.

    I used wood blocks to fill the pickup and controls cavity (and one serious routing oops)) but transition to the blocks was too obvious so I recessed it and tried two types of fillers: Latex Plastic Wood from DAP (the guy at home Depot told me it doesn't shrink as much as the regular stuff) and regular Bondo.

    I did most of the levelling sanding with 250 grit then went over it with 400. I then primed it with a Rust-Oleum Filler Primer (gray) that is supposed to have a high solid content and help fill gaps and scratches.

    I was hoping the primer would help blend the patches but they are still visible even when the primer dried to a flat sheen.

    I haven't yet sanded after the primer application, will that do the trick to bend the patches in?

    Do I need several coats of primer?

    As is said this is a learning project, so I want to get it as good as I can, even though I could live with imperfect results, some of the areas will be under the bridge, etc...

    I assume if it shows on the primer it will show under the paint and clear?

    Planning on finishing with nitro paint + clear
     

  2. dsutton24

    dsutton24 Poster Extraordinaire Ad Free Member

    Dec 29, 2010
    Illinois
    What you're trying to do is very difficult to do without the patch showing.

    Wood fillers have no place in guitar work. No matter what you do they will show through the finish. It's partly the texture of the stuff, the differing hardness than the surrounding wood, and the fact that is shrinks terribly. Not to mention that it doesn't always adhere very well to hardwoods. It's useable, to a degree, for filling small holes, cavities are another story.

    Body filler is better, but since it is harder than the surrounding wood it's hard to blend it perfectly.

    The best way to do what you want to do is to fill the cavities with a good fitting wood block, then cover the top with a veneer layer. That will give you an undetectable fill if done well. If you do a good job of fitting the patch, the patch will not show under paint without the veneer layer, but it's got to really fit well, and you have to use a glue that doesn't expand or stay plastic.

    Additional layers of primer won't help, even the 'high solids' sanding primers just don't have enough body to conceal defects. What you need is primer-surfacer. It will take a lot of primer-surfacer, and you have to allow plenty of time to let it cure and sink before you sand.

    Sand with a hard sanding block, not one of those rubber things. If you sand through, respray the entire body, don't try to spot prime, the resprayed parts will always show.
     

  3. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    Thanks. I am finding out it's harder than I thought. I thought it would be "easy" since I'm going with opaque paint, but not so.

    I never heard of primer-surfacer, is that something I can get at the hardware store or do I got to Rockler or other woodworking shop?

    I thought about using a veneer, but it felt like "cheating" with this exercise. Since I have patches both in the top and back, I'd have to veneer both sides. I have never tried veneer before. This is a low cost project so I don't know if there are cheap paintable veneers.

    I'll look at the surfacer, if not this may be a build that reminds me this stuff ain't easy. Fanos can be ordered relic'd/distressed, I wonder if I can make it less obvious by making it part of a relic job, but I have a feeling that's something else that harder than it seems.
     

  4. dsutton24

    dsutton24 Poster Extraordinaire Ad Free Member

    Dec 29, 2010
    Illinois
    Go to your local auto parts store to get primer-surfacer.
     

  5. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    Thanks again!

    The paint I want to use is Design-Master yellow which is somewhat transparent (think TV yellow) so it could look good over a veneer since it would show the figuring through.

    I've never used veneer so maybe I will look at a source for "cheap" veneer as an option.
     

  6. dsutton24

    dsutton24 Poster Extraordinaire Ad Free Member

    Dec 29, 2010
    Illinois
    You definitely don't want to use a transparent color over primer and patches.
     

  7. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    It looks fine over primer on a test piece, it's not really transparent, but shows figuring though. The best comparison I have is how TV yellow does it.
     

  8. R. Stratenstein

    R. Stratenstein Doctor of Teleocity

    Aug 3, 2010
    Loganville, Ga.
    I'm trying to get my admittedly feeble brain around trying to make a pair of humbucker-sized patches disappear using filler and a paint that allows any show-through. :eek: I think I'd lean toward dsutton's primer advice, and look to a completely opaque paint.
     

  9. Dismalhead

    Dismalhead Poster Extraordinaire

    Age:
    54
    Feb 16, 2014
    Auburn, California
    I used wood filler on top of the slab when I filled the trem route on my SG. Plugged hole, filled the cracks, then sanded and primed. Can't tell it was ever there.
     

  10. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    I think the culprit for me is the DAP plastic wood. even though I used it with a plug it keeps shrinking. I thought I had it perfectly flat, but after rubbing from pencil and sanding, I can see th repair area is still slight lower than the rest of the back. Maybe a different brand would have worked better. This is the "latex" plastic wood, I wonder if it's designed not to harden as much?

    I removed all the plastic wood patches. it comes off real easily, doesn't behave like solid wood as they claim. I filled the entire area with bondo, it's going to be a ***** to sand because I didn't knock it down very much, but hopefully I'll get a better overall surface. Even though it's a flat sheen, the primer works wellfor finding defect, I found several minor defects I had missed.
     

  11. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    Ok there is light at the end of the tunnel. My mistake was to use DAP latex plastic wood. It just does work, at least for large (albeit shallow) patches. I scraped it all off, used Bondo itself, and now I can't tell the patches under the primer.
    I have small nick left that I missed before I out the primer on and this thing should be ready to paint. I wanted a project, I guess I got one :)
     

  12. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    Minwax "high performance" wood filler is basically bondo (polyester filler, like fiberglass repair resin) with wood flour instead of some other granular filler. Either way if you're having trouble disguising the transition where it feathers out over the wood you could try automotive glazing putty which is not as hard as the bondo and not as soft as the wood and maybe is easier to sand evenly. Remember the filler will have to feather out farther than the actual border of the wood patch. Think of it as using a smoother coat of spackle over drywall compound - each layer is thinner, smoother, and covers a greater area as you work up to the finished level (not to get too far off track, but that's why drywall mud is labeled "all purpose" compound because they used to sell separate formulas for taping and a smoother one for finishing and now are trying to sell us one product to do it all).

    My biggest attempt at such a thing was filling in the trem cavity on a Hagstrom which is on the front of the guitar like a jaguar (or is it jazzmaster?). After a few years of everything shrinking back including the grey metallic paint and clearcoat, the edges of the patch did print through, if you know where to look. Maybe that's the best to hope for.
     

  13. jgriffin

    jgriffin TDPRI Member

    60
    Jul 31, 2010
    Cumming, GA, USA
    I filled two humbucker routes in a factory white SG Junior. I did a fair job of filling the holes with some mahogany blocks. Then I routed the guitar for one P-90 and sanded and primed the guitar. Life intervened and I didn't get a chance to touch it again for about 10 years. I blocked sanded the primer and you couldn't see that any work had been done. I thought that after 10 years, everything must have completely cured and stopped moving. Then I sprayed the white lacquer. Within a minute I could see the rectangles again. I just doesn't work out sometimes, no matter what you do.
     

  14. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    That is semi-transparent. It's a very poor choice over a repair. It may take several coats of highly-pigmented primer-surfacer (over the proper filler - not plastic wood) to prevent the repair from photographing through - which is a pigment issue, not a physical level one - but even then a semi-transparent (or "wash") type product is the wrong choice.

    You need to use a fully pigmented product over a patch unless you are experienced in artwork-type repairs that simulated wood grain.
     

  15. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    I ordered a different yellow from the same brand. Every other colors I tried ((well, black and light blue) were perfectly opaque, so here is to hoping the other yellow also is.
     

  16. NotAnotherHobby

    NotAnotherHobby Tele-Afflicted

    Oct 27, 2015
    Da' Magic Mittin'
    I had issues originally with some obvious lines in one of my bodies. Since I was painting i repeated a process where I sprayed primer and then used bondo to cover marks. Then I sanded with 600 grit to smooth. It took about 3 layers. The color coats went on with no visible flaws even after leveling. My biggest issue at that point was sand thu on color coats.

    Might not be applicable here but I thought I would throw that out there. My only issue was a deep crevice on the back where some veneer came off on the back. Barely noticable at this point. But as in the case of the OP I used the plastic spackle and, as mentioned here, it shrunk. Live and learn.
     

  17. papaschtroumpf

    papaschtroumpf Tele-Meister

    465
    Nov 24, 2015
    Colorado
    you applied bondo over primer? I've been sanding back to bare wood when applying bondo, so I'd love confirmation it was unnecessary for future projects.
     

  18. NotAnotherHobby

    NotAnotherHobby Tele-Afflicted

    Oct 27, 2015
    Da' Magic Mittin'
    Yep.

    I've had no problems thus far.

    I've seen guys refinish cars applying bondo over primer, and then sanding down when they had spot problems. Then again, that was back in high school...
     

  19. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    Just remember Bondo type products are really a putty made of polyester resin, so there's a bit of acetone and similar solvent in there. It's probably not too hot for most primers though and I would not hesitate to apply it over primer.
     

  20. WetBandit

    WetBandit Tele-Holic

    Age:
    27
    904
    Oct 11, 2016
    37804
    download (2).jpg

    Get you a tube of this from your local autobody supplier.

    It is basically just really thin "self leveling" Bondo, that is used for covering pinholes in more course filler and for blending filled areas.

    Great stuff, we have used it for years on plenty of cars and guitars alike with great results.
     

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