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Finishing Help Please, or: “WTH am I doing wrong?”

Discussion in 'Luthier's Corner' started by Holy Diver, Sep 13, 2018.


  1. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    I’m currently working on a couple of builds (with thread and pics forthcoming, IF I can ever get them done). Simple basic black paint scheme (sans benefit of pearls) on both, with a gloss poly clear coat. No fuss, no muss, sanitized, biodegradable, and dandruff free.

    Base coats go on fine (typically 4-6 coats), clear goes on (6-8 coats), and then sadness ensues. I get good adhesion between coats, but when I get to the sanding phase, I’m plagued by sandthroughs and witness lines, and it doesn’t seem to matter what I try. Rattle can spray on poly, wipe on poly, wet sand, dry sand, start at 220 grit, start at 400... makes no difference. Last one looked like a survey map of Appalachia.

    Today makes the fourth time I’ve sanded back and started over (at least I’m getting really good at laying on a base coat!). “Frustrated” doesn’t even begin to cover it. I’m even mulling the idea of using System Three Mirror Coat as a top coat (already have it on hand to use on one of the fretboards).

    I have officially reached the stop-me-before-I-kill-again state. Any help would be so appreciated.
     
    Bass Man Dan likes this.
  2. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Intergalactic Mind Space
    Song Surgeon sofware
  3. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    Here's your issue. I typically use at least 20 coats of clear. What kind of clear are you using?
     
    Gilmourisgod and Spidey2112 like this.
  4. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    First thing I tried was automotive clear. Specifically, VHT Wheel Paint poly:

    VHT Paint Wheel Polyurethane Gloss Clear 11 oz. Aerosol Spray Can Ea SP184 | eBay

    Then I tried Watco Wipe-On Poly, and the witness lines got worse.

    I can see how more coats will help with sandthroughs, but will that make a difference with witness lines as well?
     
  5. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    I'm not sure that wheel paint is made for multiple coats and then wet sanding. Do the instructions indicate that is a suitable use?

    Witness line occur when the subsequent coats do not "burn in" to the previous coat. Some paints just don't do that regardless of the application. Nitro will do it almost always. I use water based poly, and lay on 5 coats daily, within a half hour of each other. That allows each coat to burn into the previous one, as it's not cured. The following day, I sand lightly with like 600 grit, just to rough up the surface, and that, apparently, allows the subsequent coats to "burn in". Never had a problem with witness lines (except for my current project, which is a different story).
     
    Holy Diver likes this.
  6. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    The wheel paint is made for multiple coats. Whether it’s okay to wet sand it is unclear; instructions didn’t say NOT to do it, FWIW.

    As for your process, that sounds like the root of my issues. I was laying on one coat a day of the wipe-on and waiting a day between coats. Funny, the instructions never let you in on the subtleties; they’re so sweet about that. :D

    You’ve been amazingly helpful. This time next week, when my (hopefully LAST!) base coats have cured, I’ll try that out.

    Thanks so much. You’re a goddess among insects.

    EDIT: Consequently, what are you working on now that witness lines are an issue?
     
    mapleglo likes this.
  7. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    I'm doing a 4 to 5 string conversion on a Rickenbacker. I plugged up two of the tuner holes, so I could drill three evenly-spaced tuner holes on that side. I then, of course, had to refinish the headstock. The point at which the re-finished portion meets the factory paint on the neck, there's a witness line. I expected it, as I use water-based poly, and I believe the clear on the Ric is some kind of conversion varnish. No chance of that burning in. It's on the back, so no one but me will see it, and I *don't* want to have to refinish the whole neck or entire bass.
     
  8. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I hate to be snide, but welcome to the world of finishing guitars! Believe me, we all have gone through this.

    To back up, your big problem is that you are trying to smooth out the finish in the color coat step. As you've found out, that doesn't work very well. Sand-throughs, witness lines, mismatched patches, etc.

    You need to do almost all of your sanding in the base coat stage. Lay on coats, sand, lay on coats, sand, etc. until the surface is smooth and nearly perfect. Almost ready to buffed out. Only then do you spray on the color coats, as smooth as you can. Don't sand the color coats. They are fragile. When the color coats are right, you lay on the clear top coats. Put on the clear thick enough that you can lightly sand out and dust or minor orange peel, without going through into the color coats.

    With that said, gloss black is a particular problem. When you put a lot of clear over black, it can end up dulling the black, making it greyish or bluish. It depends on the paint and the conditions. So, on all gloss black instruments, we'll often skip the clear top coats. Build up a good layer of black, and then do the final light level sanding and buffing right on the black. Like I said above, get it smooth during the base coats. Then the final sanding of the black is very light and should not be going through layers.

    That's the important thing. It all comes down to the preparation in the early stages. You shouldn't be sanding the black enough that you are going through layers. You shouldn't need to.

    Just so you know, a full gloss black finish is probably the most difficult finish there is to do well. I've been struggling for years doing them.
     
    Last edited: Sep 13, 2018
    Beej, nolezmaj, Spidey2112 and 3 others like this.
  9. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    I feel your pain. I’m doing custom white-on-black waterslide decals on my headstocks (was front and back at the time, now just front) and about had a come-apart when the tuners for one of them had to be sent back, and the screw holes on the replacements didn’t line up or hide the old ones. I ended up filling the holes and repainting half the headstock while trying to preserve the half with the decal (which was already under multiple coats of clear). What a large and festive PITA.
     
    mapleglo likes this.
  10. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    Oh, and for what it's worth, wet sanding the clear (or in the case of black, as Bruce points out, top black coats) I never start with lower than 800 grit. I prefer to start with 1000 grit. Anything lower is just too aggressive, and will cut through to your color coats.
     
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  11. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    Feel free to snide away Bruce. I’ve taken harder abuse, from people who say they like me.

    Lots of food for thought there. Hearing a pro talk about how hard it is to do a gloss black finish does no end of good to my poor bruised ego. Thanks so much for the tips.
     
  12. Bruce Johnson

    Bruce Johnson Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yep, I forgot to mention that. The final level sanding should be 1000 and up. If it takes more than that, then the surface underneath wasn't smooth enough to put on the color coats. Or, the top coats are sprayed on too rough. You need to get your spraying technique down so that those top coats lay down smooth and flow out to a pretty nice gloss by themselves as they dry. The final level sanding is to take off dust and smooth minor patches of surface roughness.
     
    BassHappy and mapleglo like this.
  13. Like Bruce said; the underlying preparation is where it’s all about. It doesn’t get the glamour of the top coats, but you have to have it smooth as a baby’s bottom.
    If you can stand starting from scratch again the spray bombs from Guitar Reranch are nitro lacquer and the coats will burn into each other.
    I thought for sure your problem was going to be blushing from the excess humidity in the air so that’s another thing to concern yourself with. Fortunately we are leaving summer so you should have some good spraying weather ahead.
     
  14. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois
    Your process is very different from my own but I use catalyzed polyurethane automotive paint.

    I can't speak for how others apply paint but my background is in automotive finishing and I've successfully used it with guitars for years.


    1) prep the surface with 400 sandpaper

    2) 4-6 base color coats

    3) Wait the proper time described in the instructions before clearing

    4) wet sand color coat with 2000 (this step is optional)

    5) 6-9 clear coats

    6) allow to cure

    7) wet sand with 1000, then 1500, then 2000.

    8) polish with 3M 3 stage system (or similar).


    I only sand to prep body (with 400) and then after clearing (starting with 1000).

    I've never tried to do as much sanding as you have and certainly not with such coarse paper, but I imagine I'd also be burning through the paint if I followed your process.
     
    Last edited: Sep 13, 2018
  15. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois
    Looking more carefully through the previous posts I see some excellent advice.



    This. I wouldn't even consider sanding the clear coat with anything coarser than 1000. And I would never dry sand.

    I promise you that if you take this advice and start with the 1000 wet sand paper, you'll solve your problem for good.

    As for needing to use 20 coats of clear, I consider that to be overkill. I've never needed more than 10 to get a deep, flat, mirror finish.
     
    Last edited: Sep 13, 2018
  16. Holy Diver

    Holy Diver Commercial User

    Aug 14, 2018
    East Tennessee
    I was endorsed by Gallien Krueger and ESP in 2002 but am no longer on either company’s roster.
    I’m very encouraged by all the great advice and feedback.

    I’d searched... and searched... and searched for guidance up to this point and come up essentially dry. The first-time builder can find all kinds of info here about rubbed, dyed, stained, and tru-oiled finishes (as there should be; they make for beautiful instruments, and the builds I’ve seen here using those have been masterpieces), but precious little on doing a simple (!) solid color gloss, and even less on the details of the process. Something as simple as using the proper sanding grits, as I’ve so painfully discovered, will make or break you, and all this vital, need-to-know information had up to now eluded me.

    Thanks again, all of you.
     
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  17. HaMMerHeD

    HaMMerHeD

    May 20, 2005
    Norman, OK, USA
    I start wet sanding at 1200 grit, using a black rubber 3M squeegee (from any auto parts store) as my sanding block.
     
  18. Spidey2112

    Spidey2112

    Aug 3, 2016
    When I built my kit, I used 1 can each, of primer, paint, and top coat (nitro). Each provided 4 applications...

    ... I think the primer was ok with 4, but I easily could have applied an extra can of paint and top coat, so there would have been 8 of each.

    It didn't turn out too bad, especially for my first time. I learned it takes more patience and time than I thought it would.
     
  19. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    I put 30 thin clear coats on my black bass, no sand through, but I was excruciatingly slow and careful, particularly at edges. No secret here, you have to build up some thickness.
     
    Spidey2112 likes this.
  20. Spidey2112

    Spidey2112

    Aug 3, 2016
    Gil, you probably used a spray gun... I'm not buying 14 cans of paint/nitro...

    ... :laugh::laugh:!
     

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