Open grain woods like oak, ash, and walnut present unique finishing challenges. Those beautiful pores that give these species their distinctive character can also trap air, cause uneven sheen, and make achieving a smooth surface frustratingly difficult.
Understanding how to work with open grain—rather than against it—opens up finishing possibilities that highlight wood’s natural beauty.
Understanding Wood Grain Structure
Trees grow in annual rings, producing alternating bands of earlywood and latewood. In ring-porous species like oak and ash, the earlywood contains large vessels that appear as open pores on the wood surface. These pores run the length of the board like tiny straws.
The key to success with unfilled open grain is building up thin coats and buffing between applications. This creates a soft sheen that highlights the wood’s three-dimensional texture without pooling finish in the pores.
Pore Filling Techniques
When you want a glass-smooth surface, pore filling becomes essential. Several methods work well:
Commercial Grain Fillers
Paste wood fillers come in various colors to match your wood species. Apply liberally across the grain, forcing filler into the pores. Once it hazes over—usually 10-15 minutes—scrape off the excess with a plastic spreader, working diagonally to avoid pulling filler from the pores.
Epoxy Filling
Thin epoxy makes an excellent pore filler for projects that will receive a film finish. Apply a seal coat first, then flood the surface with epoxy thinned with denatured alcohol. The epoxy self-levels into pores and cures crystal clear.
Finish-Based Filling
You can fill pores with the finish itself through repeated applications. Apply shellac or lacquer, sand flat, repeat. This “French polish” approach takes time but produces stunning results with perfect color match.
Common Open Grain Mistakes
Rushing the process: Allow fillers to cure completely before topcoating. Trapped solvents cause clouding and adhesion problems.
Wrong color filler: Test fillers on scrap. Wet filler looks different than cured filler, and the wrong shade stands out harshly.
Skipping sealer: A thin seal coat before filling prevents filler from staining the wood between pores.
Using Natural Beauty
Whether you fill the grain or celebrate it, open-pored woods reward careful finishing with depth and character that tight-grained species simply cannot match. The extra effort pays off in pieces that catch light and draw the eye for generations.
