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Thread: Best Clear Grain Filler for Walnut Guitar?

  1. #1
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    Best Clear Grain Filler for Walnut Guitar?

    I have to put a clear finish on my walnut guitar body. My luthier says I need to fill the grain with a clear product before applying nitro. I have been researching this, but as usual, I'm confused.

    1. I thought I wanted a clear and colorless product, because I want the wood to show through, but now I'm reading that a little dye will make the grain pop out. Is that right? If so, what dye should I use?

    2. I've seen lots of products recommended for filling. The two that stand out are shellac and epoxy. Shellac seems simpler, but a lot of people love epoxy, so there must be something to it. Which is better?

    3. I believe my guitar has a few nearly microscopic holes in it where planing pulled on the figuring. I've seen superglue recommended for these holes. Is that the best way to go, or should I just keep applying filler until I get a flat surface? Also, will the little jars of acrylic glue work? They have nice thin application tubes that ought to be useful for applying tiny amounts of glue.
    Sometimes you have to man up and throw in the towel.

  2. #2
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    Were it me, I'd seal with de-waxed shellac and then use Behlen's clear filler followed by another seal coat of the shellac. Simple and made for the job.
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  3. #3
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    I like to use shellac as a grain filler, Garnet shellac will give it a bit more color than the blonde. Use de-waxed it is optically clear, hard, fast drying and color fast.

    I brush on 3 or 4 coats of a 2# cut letting it dry between coats for an hour or so. Then I sand it back to the wood, leaving the shellac only in the pores. If you sand it back and see little shiney spots then you will need to reapply 2 more coats and sand again. I like to give the shellac a few days to completely dry before I top coat... this ensures the shellac is completely dry and will not shrink in the pores after the top coat is applied.

    I have a sample board of walnut I show in class the has walnut grain filler on half the board and shellac as described above on the other half. The 1/2 filled with walnut filler the grain looks blurred on the shellac side the grain has sharp crisp, deep look to it.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  4. #4
    Quote Originally Posted by Scott Holmes View Post
    I like to use shellac as a grain filler, Garnet shellac will give it a bit more color than the blonde. Use de-waxed it is optically clear, hard, fast drying and color fast.

    I brush on 3 or 4 coats of a 2# cut letting it dry between coats for an hour or so. Then I sand it back to the wood, leaving the shellac only in the pores. If you sand it back and see little shiney spots then you will need to reapply 2 more coats and sand again. I like to give the shellac a few days to completely dry before I top coat... this ensures the shellac is completely dry and will not shrink in the pores after the top coat is applied.

    I have a sample board of walnut I show in class the has walnut grain filler on half the board and shellac as described above on the other half. The 1/2 filled with walnut filler the grain looks blurred on the shellac side the grain has sharp crisp, deep look to it.
    Yes! The garnet will help pop your figure as you sand it back also. It seems like nearly everything I do starts with shellac these days.

  5. #5
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    So I would need to order shellac flakes instead of relying on a prepared product in a can or aerosol?
    Sometimes you have to man up and throw in the towel.

  6. #6
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    I like shellac from flakes much better. Then spray can is a very thin cut; I'd guess: 1/2# to 3/4# cut. It will take a while to build it up, so you fill the grain.

    It will workwith either, the Zinsser Seal Coat is a 2# cut of dewaxed shellac so it will build much faster than the spray can.
    Scott

    Finishing is an 'Art & a Science'. Actually, it is a process. You must understand the properties and tendencies of the finish you are using. You must know the proper steps and techniques, then you must execute them properly.

  7. #7

    Careful consideration required

    Before you go off and use this and that to seal, pore fill and seal again you need to know what your topcoat is going to be.

    Something to realise is that a guitar finish a fair bit different from a furniture finish in that the desired film build is much thicker. These thick hard finish films are pretty sensitive to just about everything so you want to make sure that the adhesion between your sealer and top coats is excellent and that the two products pretty much behave the same way when it comes to temperature changes and wood movement. (look carefully into the topic of cold checking and lacquer).

    Nitrocelluslose lacquer is a very common choice for the project that you have undertaken. If you too are going to use NC lacquer then I would strongly suggest that you choose your lacquer and then look to the manufacturer of your chosen topcoat for their recommendations when it comes to sanding sealers and pore fillers, solvents and rertarders etc.

    If you are going with NC then the sealer of choice is typically a vinyl sanding sealer that uses the same solvent/thinner as the top coat.

    Also look into tinting the pore filler. You can get a very nice effect by tinting the pore filler black or some other colour. Remove all filler outside of the pores prior to sealing and I think that you'd be very pleased with the results.

    I'll mix and match to get the finish that I want but I would never just wing it on a project like yours unless I tested on scrap first. Often times not using the manufacturer's solvent/thinner with a given top coat will produce inferior results.

    You're too far into the project to wing it now. Pal up with your local finishing supplier and you'll stick the landing.

  8. #8
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    It's funny how much people's advice differs. Even when you ask people who know what they're doing, the methods and materials are completely different.

    I decided to try shellac with nitro over the top. Epoxy scares me. I can just see it, congealing into horrifying mounds and runs while I'm trying to get it applied. I'm finishing scrap first to see what works.
    Sometimes you have to man up and throw in the towel.

  9. #9
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    I typically use shellac as a bridge / sealer coat inmost of my finish schedules. However, in this case I would vote for an oil-based grain filler with the shellac as a bridge coat before the NC. Check out Guitar Reranch site as there is some good info there. For something as porous as walnut I worry about shellac shrinking over time and revealing a stray poore here and there - especially if you are going for a high gloss finish. While it has nothing to do with the poore filling, with a guitar you also need to worry about the exposire to body oils and other environmental factors (beer / liquor possibly if this is a guitar you will be using for gigs and such).

    http://www.reranch.com/
    Last edited by Larry Fox; 12-25-2010 at 10:07 PM.
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  10. #10
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    Two importatnt things to consider ...

    1) Almost anything will stick to shellac and shellac will stick to most anything ... this makes shellac a good choice for filling/sealing the grain.

    2) The most compatable sealer for any finish is a thin version of that finish. If you're topcoating with NC .. use it also as your filler/sealer. Apply a few thin, full, wet coats .. allow it to dry thoroughly .. then sand back to bare wood, leaving the finish in the pores. Topcoat as needed with a very light sanding in between coats just to knock off any dust nibs. Lacquer is a very "HOT" finish,and as such, each coat will melt into and bond with the layer(s) under it, so there's no need to sand for adhesion .. only for smoothness.
    FINISHING : NO ART & VERY LITTLE SCIENCE ... just a learned skill that requires a bit of practice and patience ... anyone can learn it.

  11. #11
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    I would use a very sharp scraper first. I have had this problem with rosewood on an acoustic that I built. Gently scrape it, shellac it and then fine sand, and repeat with the shellac and sanding until its slick. After this comes the final finishing.

    Building guitars is the best!

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