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.

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.

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.

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Originally Posted by Scott Holmes

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.

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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.

So I would need to order shellac flakes instead of relying on a prepared product in a can or aerosol?

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.

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.

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.

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/

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.

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!

Scott,

How are you, hope all is well.

Just responding to your comment on using shellac as a grain / pore filler...

I like this idea, and I have used it in the past (unknowingly) on a classical guitar...

I am finishing a walnut guitar body: English walnut top (lighter color), and black walnut back, 12” x 11” small body

I am using tru oil. I cannot spray since I am in an apartment

I have assembled and finished several guitars and an oak amp cabinet over the years.

I have used oil polys, water poly Crystalac Brite Tone, oil finishes. I thought I would like Crystalac, but it just does not work well, does not buff up, and a lot level sanding.

As long as the surface is scratch free and pore filled, and one puts on thin coats, (no wetsanding), it will come up pretty nice: streak free, smooth, glossy, etc.

I discovered first hand if I wet sanded tru oil with 600 or less, scratches would always result, so wet sanding did not make sense after that.

My current challenge is filling pores in the walnut (black walnut long streaky pores): I have used most of them: timbermate, aqua coat, Crystalac Wood Grain Filler, GluBoost (I like that for repairs and deep holes), etc.

Timbermate is a mess, Aquacoat is inconsistent and a mess, Crystalac is ok, powders up white…

I got the walnut body to 320 with my orbital sander and Abranet 320, and zero scratches.

I have blonde and garnett Weller flakes, but in So Cal, no access to alcohol to dissolve the flakes, silly really. I do have access to Acetone, but I am not sure I can use Acetone to dissolve shellac flakes?

If not, I am going use Zinsser Sealcoat, 100% de-waxed shellac.

You say 3-4 coats #2 cut, and I think one coat = 1 hour dry time in between coats, so 4 total hours.

I know shellac has to dry at least an hour before sanding.

So sand off tru oil to bare wood with 320, 4 coats of #2 shellac, 4 hours to dry.

Do I sand back with same 320?, then 400, then 600, then 800.

I do find that going to higher grit 800 = pretty much zero scratches, and ready for tru oil.

Thank you in advance,

Thank you, John K

John K, noting that the post by Scott and the rest of the thread are 10+ years old. But I wanted to put a plug in for the grain filler that Stewart MacDonald sells. I think its a lot smoother than Crystalac, my usual. You say you're going to finish with Tru Oil (linseed oil with some other oils and solvents). If you fill and/or use shellac, won't that prevent any penetration by oil into the wood?

Sand back to bare wood, so shellac is only in the pores...


Cuts down on how many coats of tru oil it takes to fill pores...