How to properly finish a guitar

Discussion in 'Luthier's Corner' started by cv115505, Jan 21, 2014.


  1. cv115505

    cv115505 Supporting Member

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    I have already posted asking about neck stability.... now I need to know about finishing.... I'm looking to do metallic gold for my finish... I have all the spraying equipment, but none of the know-how. To get a nice gloss metallic gold finish what kind of paint would I need? What prepping must I do to the wood beforehand (probably going to be a walnut or mahogany body)? I don't even know what questions I need to ask so the more info on this the better.... I know this is busch league, but I'm mostly doing this as a learning experience because I simply don't know how to do it... Any advice is much appreciated.
  2. HaMMerHeD

    HaMMerHeD

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    Location:
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    Walnut and mahogany are both porous, open grained woods. You will need to fill the pores with something. There are numerous materials for that. Timbermate pore-filler is probably one of the more popular ones. Pacer Zpoxy is used a lot, as well as Zinsser's dewaxed shellac. The Timbermate and Zinsser products dry fairly quickly. Zpoxy is an overnight cure.

    Before filling the grain, some people spray a light coat of something (shellac, lacquer, vinyl sealer, clear poly) to seal the grain. This helps keep the filler and eventual top finish from sinking into the wood after curing and showing the grain, or so they say.

    Since you are doing a solid color, the color of the filler doesn't matter much.

    After filling, some people spray on another thin sealer coat. Some people also use the filler/sealer basically as primer. As near as I have been able to tell, most people don't use actual primer on guitars. With all the other crap on the wood to prep it for color, it's probably just not necessary.

    After filling and sealing, you'll need to sand it to 400 or 600 grit or so to make a nice, flat, smooth surface to which the color coat can adhere.

    I don't know what kind of paint you'll need to use. Find a metallic gold color that you like, then use a compatible clear coat. My understanding of spraying metallic paint is that you will want to use several very light coats, followed by a couple of slightly heavier clear coats just prior to wet sanding. After wet-sanding the color coats and first clear coat, proceed with adding and wet-sanding additional clear coats.

    Reranch has this to say about spraying metallics:

  3. cv115505

    cv115505 Supporting Member

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    I might just do a solid color haha sounds much easier, and I have plenty of solid colors I like
  4. HaMMerHeD

    HaMMerHeD

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    It's really not more complicated. It just takes a bit more time, because you need to use more, lighter color coats.
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  6. cv115505

    cv115505 Supporting Member

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    ok cool... would it be easier if I used a closed-grain wood?
  7. cv115505

    cv115505 Supporting Member

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    I'm actually reading up on it and I think I am going to go with Alder... Most of the basses I've had over the years that I've liked have been Alder so I'll just stick with it... Maybe as I get more experienced with this I will try something a bit more challenging. So, for Alder, what do I do to prep the wood for the paint? Since it is closed grain, I wont be using the fillers... Should I consider some sort of primer?
  8. Big B.

    Big B.

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    Hopkins just recently posted a thread showing his process for doing a beautiful emerald flake finish. I would start there and I suspect the man himself may even weigh in before long.
  9. HaMMerHeD

    HaMMerHeD

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    For alder, I'd sand the bare wood to 400-600, apply and sand a seal coat, and then start color. For the seal coat, I would use something like a shellac sanding sealer. It's cheap, easy, readily available, and it dries fast.
  10. Hopkins

    Hopkins Supporting Member

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    Going with alder over walnut is a good choice for a guitar with no grain showing. It will require no grain filling, other than possibly a random not that needs to be filled.

    About the finish, are you spraying a metallic gold paint or are you wanting to do a gold flake finish?

    Spraying a metallic gold paint is not really any more difficult than spraying a solid color, except for the fact that you have to be careful to not get any runs as they cant just be sanded out because the metallics run and distort the paint. Its best to spray them in light coats.

    Doing a metallic flake is a totally different animal. With this type of finish a colored flake mixed in a clear is sprayed onto a bass coat. With a gold flake, either gold or black works best as the base coat. You will need a gun with at minimum a 1.8mm tip, 2.0-2.5 is better, as the finish is very thick and will plug up a regular top coat gun. You have to be very even with your passes when spraying because an even application is key to getting a good looking finish, which can be difficult on the edges and inside the horns. Like metallic paint, you absolutely cannot run the flake coat, but luckily, with the flake mixed in, it is a very high solids finish and can be loaded pretty heavily without running. Don't get in a hurry to build the finish up, let one coat dry 24 hours before spraying the next. Keep building up the flake until it is thick enough for you, some flake looks better applied very thick, some flakes look better when more of the base coat is showing.

    After you are finished with the flake, it will be a very rough uneven finish, do not try to sand it level. Sanding into the flake will sand the color out of the flake and leave a silver spot. Spray at least two coats of clear over the flake, when dry, you can start lightly level sanding the clear just knocking the highest spots off, do not try to get it level just yet. Then spray two more coats of clear, then start leveling sanding. Be very careful not to sand into the flake coat, if you start seeing the color come out of the flake, stop and spray another coat.

    A few more things, this finish requires a pretty good compressor, if yours wont flow at least 5.5 to 6 cfm at 90 psi, then you will have a hard time spraying it. Volume is important, not pressure.

    Also, it requires an automotive clear, like a V.O.C. urethane. Nitro does not suspend the flake very well, and it will settle into the bottom of the cup and most likely clog up the gun.

    Here is an example of a golf holographic flake on a black base coat. A gold base coat would have given the bass a completely different look.
    [​IMG]
  11. friskinator

    friskinator Supporting Member

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    I'm currently in the midst of doing a refin on a Strat body, and have run into a possible issue. I'm using Reranch products, and the body was originally finished in black poly.

    I've done several rattle can nitro-over-poly refins before, and as recommended, I scuff-sanded the original gloss, then sprayed white primer. After 3 coats of primer (2 base coats, then light sanding with 320, then another coat), there are some spots that are still showing through that I can't seem to cover up with primer. It almost looks like wood grain (especially in the second pic), even though I didn't get anywhere close to the bare wood. These are not sand-throughs in the primer.

    I'll be using Lake Placid Blue Metallic for the color, and I'm concerned that these spots will be visible after I start spraying color. Any advice on how to fix this, or should I just go ahead and start with the color?

    I've attached some pics below:

    Attached Files:

  12. Hopkins

    Hopkins Supporting Member

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    The blue should cover those spots up with no problems
  13. lbridenstine

    lbridenstine

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    I wouldn't cover up walnut or mahogany with paint, those should be natural in my opinion. Alder would probably be good if you want paint.
  14. cv115505

    cv115505 Supporting Member

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    I'm going with regular gold metallic paint
  15. Hopkins

    Hopkins Supporting Member

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    Your prep work is key. My method is to seal the body using the same clear I would use for the final top coat. This insures that everything is compatible, and it gives you a very hard sealer coat.

    The body, especially around the end grain is going to absorb a ton of the sealer on the first coat. Don't try to apply more finish, just let it dry, lightly scuff the surface with 320 grit and apply another coat.

    If you are using a two part urethane like an automotive paint, the proper application is to spray a light tack coat, let it flash for 10-15 minutes then spray a medium wet coat and let it dry for about 12 hours.

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