Filling Open Grain Wood

1. After applying your stain and letting it dry, seal the wood with a wash coat of finish. A wash coat is usually made by thinning lacquer or shellac with one part finish to three parts thinner. If you use varnishes then you may have to experiment although you can use shellac in an aerosol. It is best to spray the wash coat on using light coats. The goal is to seal the wood without clogging the pores because the wood pore filler has to be able to penetrate and stick to the inside of the pores.
2. I use colored fillers like dark walnut, dark mahogany or black. By using a lighter stain on the wood and sealing it so it doesn’t absorb the color of the filler, you will accent another feature of the wood’s grain.
3. Traditional wood pore fillers contain linseed oil, powdered quartz and color pigment. The linseed oil necessitates that filler dry over night at 65 to 70 degrees. If your shop is cool, give it two days. If you apply finish before the filler dries the filler may lose its color and cause a condition known as “Grey pore”.
4. When the filler is dry, lightly sand the surface to remove some more of the filler residue and give the surface some scratches for better adhesion of your top coats.
5. Don’t expect the wood pore filler to completely fill the pores. It shrinks as it dries. You can apply a second coat after the first one dries. However, the final filling must be achieved with coats of finish carefully sanded so you don’t disturb the color work or expose any raw wood.
6. Be sure you remove all the filler residue with burlap and/or rags. Residual filler under the finish will look cloudy. I use dowels sharped in the pencil sharpener to get the excess filler out the cracks and crevasses. Since the rags have linseed oil on them, be sure to depose of them properly.
7. If you are going for a glass like surface, often called a “full finish˝ or “piano finish˝, you will have to let the finish cure for a week so it can shrink back, then do your final sanding and top coating.

That’s the fastest and easiest way to fill the pores in open grain wood unless you have an assembly line for finishing and ovens between step like a furniture factory!

Guy Senneville replies: I find that the easiest way to fill grain is to first apply boiled linseed oil. Once this has soaked in, apply another coat and while still wet, sprinkle with rottenstone. Work this slurry into the pores. When left alone it will “haze˝ over. Remove the haze with a rag by rubbing against the grain. Keep in mind that the second coat of oil can be colored with aniline dye. If you find that the color is too dark, remove some with clear oil. The rottenstone will be a dark grey to black pore filler. Let dry for about a week before applying a topcoat. You may also want to give your piece a once over with 0000 wool before applying a topcoat.

John Whiteside replies: First sand (and/or plane and scrape) the wood to a finish-ready surface. Then mix some epoxy. Choose the set-time of the epoxy so that you will have time to apply it to the entire surface before it starts to set. Apply the epoxy with a plastic scraper and remove the excess with a rubber window squeegee in a direction perpendicular to the long axis of the pores. The goal is to work epoxy into the pores, not to coat the surface.

When the epoxy has cured, lightly sand the surface. The goal is not to remove wood, only to remove epoxy roughness on the surface. If it is a really deep-pored wood, such as oak, you will likely need to repeat this process three times. I have had really good results on Indian rosewood with two applications, capable of taking a mirror-gloss finish with no trace of pores whatsoever. That is, there are no visible depressions under even a harsh raking light and no telegraphing color differences between the filled pores and the surrounding areas. The epoxy-filled pores take their color from the surrounding wood.

Do a test to be sure that your final finish (be it shellac, varnish or lacquer) sticks to the brand of epoxy you are using. In the event the project calls for staining the wood, experiment with staining it prior to the epoxy fill. Another big advantage of this method is that it works for minor gaps and voids as well as pores.

Another method of pore filling that is relatively easy, and really inexpensive, is to use egg white. Beat egg whites to the soft peak stage. Be sure there is no yolk in the whites. Then brush the egg whites onto the wood to be filled. Also, wet 400 grit sandpaper with egg white and sand vigorously. What happens is the sanding creates an egg-white-and-fine-sawdust slurry which works into the pores. Also, apparently, the abrasion causes a beneficial change in the protein molecules of the egg white. Once you have made a good amount of slurry, squeegee the residue off, always in a direction perpendicular to the grain. Let dry and lightly sand with very fine sandpaper.

This egg white method requires maybe twice the applications to achieve the same results as the epoxy method. Three applications worked well on Indian rosewood. Deep pored oak might be a challenge—I’d use epoxy for that. Also, the egg white lightens the wood very slightly. Do not attempt to stain the wood after doing this as the egg white won’t hold stain.

Why haven’t I mentioned commercial pore fillers? I have found them to be expensive, messy, difficult to apply, and to produce a poor color match between the filled pores and the surrounding wood.

BJ Tanner replies: I use Sherwin Williams, Sher-Wood filler D70T1. Read the instructions—reduce with naphtha by 50% (1:1 ratio). If it is not reduced, it will be very hard to apply and remove. It also will not fill correctly. I apply the filler with a throw away brush. After a couple of minutes, I remove gross excess with a dull scraper and finish with a cotton rag. This filler may be tinted with products that are compatible with oil/naphtha. This is a commercial product that may be ordered through any Sherwin Williams store.