Trouble with Grain Filler

[Gordon Bellerose]

I've been struggling somewhat with grain filler.
I have a solid mahogany body that I have finished, and have had to sand the finish off twice!!

I have been using a clear waterbase grain filler called Crystalac. It is a gel type substance that you wipe on and trowel or wipe off.
I put on two coats and then fine sanded, wiped on another coat and fine sanded again. As soon as I put the first coat of clear, there are marks showing up that look like scratches.
I sanded everything off, filled again three coats, being very careful to sand only with the grain.

After 2 or 3 clear coats the pits started showing up. Pits that look like unfilled mahogany.

I have now purchased some EM 5000 waterbase clear coat, that can be sprayed. I am going to sand everything off AGAIN!! and start over.

Has anyone else experienced something like this?

[Mark Swanson]

That clear grain filler just does not work, and I have never known anyone who got good results with it.

[G.S. Monroe]

Yea, it hasn't worked for me either. The best way I know of to fill grain and seal wood is to wet sand with 400 grit and alcohol based shellac. It's a little bit of work, but a whole lot more reliable to just go "Old School". De-Waxed Shellac flakes will give you a wonderful base coat/sealer for just about any finish you want to use.

[Gordon Bellerose]

Has anyone tried the Target product? I believe it is EM HF5100 Clear Grain Filler.

[Denny Boyce]

G.S. just to be clear, are you saying that you pore fill and build a base with shellac wet sanding between coats with 400 grit. Or that you wet sand your bare wood with 400 grit and then apply the shellac? Thanks, Denny.

[Michael Lewis]

Wet sand finish, dry sand wood.

[Waddy Thomson]

He's talking about wet sanding with shellac as the wetting agent, and working up a slurry and forcing into the pores. It works, but you can only do small areas at a time due to the fast drying of the shellac. Egg white slurry also works, but does have a shrink back issue. Shellac also shrinks back some as it cures, so neither is perfect. I have tried Crystallac, and I didn't have very good luck with it either.

[Mark Swanson]

So what's wrong with using traditional oil-based fillers? I have the best luck with those. The water-based colored stuff works good too but that clear is useless.

[Gordon Bellerose]

So what's wrong with using traditional oil-based fillers? I have the best luck with those. The water-based colored stuff works good too but that clear is useless.

Is it because you can see where you have filled, easier with the colored stuff?

Mark, I am finishing in waterbase finishes for a few reasons.

1. Anti VOC laws here in Canada make it very hard to buy many oil-based products. Online suppliers can not ship some oil-based products to Canada.
2. I do not have an explosion proof fan in my spray booth so Nitro, which I can not buy anyway, is out of the question. I wanna keep the small amount of hair I have.
3. Most if not all, oil-based fillers are not compatible with most water-based finishes.
4. I do find the colors I'm able to get with water-based stains seem to be more vivid. Maybe that's just my opinion, not an actual fact.
5. Environmentally the water base stuff is much better.
6. It seems easier for me to get the colors I want if I use clear filler. Maybe that is just my inexperience talking.

I'm going to try the colored water-based filler, if the Target EM 5100 clear filler I just bought does not work out.
I do appreciate everybody's help with this.

[Barry Daniels]

The water based filler dries a little faster than oil-based so be prepared for that. (A wet rag or spray can soften overdry filler) Sanding the dried residue is difficult so I find that it is easier to wipe off filler before it dries. For color its works best to keep the filler a shade or two darker than the wood.

[Ron Belanger]

If you are using a waterborne finish, epoxy makes a very good grain filler. I use system 3 and others have used z-poxy and west systems. I seal with shellac and then fill with epoxy usually two to three applications. Then follow your regular spraying or brushing schedule.

[Gordon Bellerose]

If you are using a waterborne finish, epoxy makes a very good grain filler. I use system 3 and others have used z-poxy and west systems. I seal with shellac and then fill with epoxy usually two to three applications. Then follow your regular spraying or brushing schedule.

I've heard of that before. Is it a bit easier to work with the epoxy?
I have some G2 slow drying, 2 part epoxy that I use for gluing inlay.

Do you need to sand in between applications of the epoxy?

[Ron Belanger]

I use the SB112 which is a laminating and coating resin. I am not sure if the epoxy glues are suitable for pore filling.
Since I use small quantities I mix by weight rather than volume. SB112 uses a ratio of 100 resin to 44 hardener. I don't want to have any issues with the epoxy not hardening properly. I mix anywhere from 2 1/2 to 10 grams at a time. I found a small inexpensive gem scale that measures to 1/10 of a gram.
I add an equal amount by volume of a silica thixotropic thickener. It makes it about the consistency of cold cream.
I apply it with a rubber squeegee pushing it in the pores and removing as much as possible from the surface. I let it harden overnight and sand or scrape any bumps or ridges flat and apply usually two,sometimes three more coats until the pores are filled.
There are excellent detailed instructions by Mike Doolin or John Greven (Check the Grafted Coatings KTM9 page) as well as a number of videos on YouTube. I recommend reading them thoroughly and watching the videos and practicing on scrap before you attempt it on your instrument.

[Eric Baack]

I really liked how the water based colored wood filler brought out the grain when I used the dark walnut on my PRS style electric. Fairly easy to apply, like timbermate I believe. I used varathane from menards. Just thin it with water, squeegie it on and off working it into the pores. I think it would have gone a bit better had I wet the wood first to keep it from sucking the moisture out of the filler too fast.

[Gordon Bellerose]

In the epoxy method mentioned, how does the epoxy affect stain?
Do you stain prior to filling, or can you stain after filling?

[Barry Daniels]

Staining would be very difficult after an epoxy fill since it really seals the surface. But you could certainly stain the wood before applying epoxy. Just make sure they are compatible.

[Gordon Bellerose]

After listening to all of you good people and reading a whole lot of new information, I've decided to do as I've been told!! My wife would enjoy reading that!
First, I have again sanded the body down to bare wood, scraping in the hollows and curves to get a real nice smooth finish. I wiped it down with Naptha and it looks good and clean, no scratches or marks.

Second, I will seal with shellac. I'll probably do 2 or 3 coats of thin Orange shellac. 1 - 1 1/2 pound mix, sanding lightly in between coats.
Please let me know if this is too thin, or if I shouldn't sand in between coats.

Next I will do the grain filling with epoxy. Again 2 or 3 coats.
After that I will start spraying my finish coats.

Does anyone know of any problems I will run into with this method?

[Arnt Rian]

I like to keep the filler in the pores only, to have a better control over finish thickness, among other things. Any colors are either applied directly to the bare wood and/or in the first top coats. So the schedule, minus colors, is apply filler, sand back to bare wood, apply clear coats, level and polish. These days I use CA glue as a filler, both because its fast, clear, and it doesn't shrink back. I use medium viscosity CA glue, which can be purchased in large bottles directly from Star bond, for a reasonable price. It can be beneficial to leave a thin layer of CA as a seal coat, before athe clear, as it will bond to wood better than many finishes. Some epoxies, such as the popular Z-poxy finishing resin, is slightly amber colored, so you either have to sand back to wood everywhere, or leave a comple seal coat, or it will end up looking blotchy. It also soaks into end grain, such as around the neck heel and hearstock tranistion, making these areas somewhat darker than the rest.

The fumes are the worst part about CA as a filler...

[Tony Costa]

I have used Z-Poxy on 8 guitars and an ukulele with great success. I have also used TimberMate successfully as well. Timbermate is really fast because you can sand it in about 20 minutes. Z-Poxy has a long enough working time that you can get it into the pores pretty readily before it starts to gum up. Easily 5-10 minutes, probably more. I have never needed more than 5-10 minutes to do a back. Plus, it is very forgiving with the mix ratio. I just draw out an equal length line of each component on a piece of cardboard, then mix them up.
One tip that works well is to scrape it off with a razor blade after it dries. I can more easily see if I have missed pores that way. Your coats should be very thin once you squeegee the excess off while it is wet, so it takes only a few minutes to razor-blade-scrape off the excess once dry. Before my next coat, I will rough up the surface with a scotchbrite pad or steel wool, then recoat. Usually it takes me 2-3 coats. I do not sand back to bare wood before I apply my finish (nitro lacquer). I may get some bare spots, but before the lacquer, I will mix up a batch of Z-Poxy and thin it with denatured alcohol, then apply it with a pad to make sure all of the wood is coated. Any spots without Z-Poxy will show up when you apply your finish, so you want to make sure there is either no bare wood, or ALL bare wood.
TimberMate is water based, is compatible with just about every finish, and dries really fast, so you can do multiple coats in an evening. By the time I reach the end of the back, the first section I filled is usually dry enough to sand. I prefer Z-Poxy for the way it pops the grain, but TimberMate works very well. I tend to use it on necks in the following manner:
First I apply the filler, sanding back so it is only in the pores.
Apply a coat of Danish Oil to bring out the grain
I then finish my necks with MinWax Wipe on Poly and they look like glass, but without that look of a think plastic finish.
Hopefully this was helpful. If anyone has more questions about Z-Poxy, let me know. I am certainly no expert, but I have used it enough times to be comfortable with it.