Gaps, whether they’re large or hairline, can be annoying and unsightly. I also feel like I’m judged as a woodworker by how tight my joinery and glue-ups are. Here are several methods I use to deal with them.
How to Fill Gaps in Your Glue-Ups as a Woodworker
Wood Filler: This is my least favorite method. Most commercially sold wood fillers never really match the color of the wood you’re using. Some manufacturers do a good job matching raw wood color, but once you apply a finish, the filler stands out as a light streak because it doesn’t absorb the finish the same way the surrounding wood does. If you go this route, I’d recommend using a filler that’s one shade darker so it looks like it could be a knot or streak in the grain, helping disguise the fact that you used filler at all. One other thing to consider with wood fillers is that they can shrink as they dry, which sometimes means multiple applications if the dried filler falls out as a result of that shrinkage.
For commercial wood fillers, I usually use Timbermate. They have a decent selection of colors, and it doesn’t shrink unless you’re filling large holes. At that point, it’s probably not the right method for the job.
Sawdust Method: Especially on flat surfaces, if I’m dealing with a hairline crack, I’ll cover it with PVA wood glue and sand over it, creating a glue and sawdust slurry. Then I push that slurry into the crack, usually with the pressure of the sandpaper as I sand. In most cases, this makes the crack disappear completely.
Wedge Method: This method works great if you have a gap in a through tenon or dovetail you’re trying to hide. Cut a wedge from the same wood type that will fit the gap, add a little glue, then drive it into the gap. Cut off the excess and sand flush.
Pro tip: since every piece of wood has color variation in it, if you take the time to match the color variation in your wedge to your workpiece, the wedge will disappear once finished.
Epoxy Fill: When none of the above methods give you the results you’re looking for, or the gap is too large to simply rub some filler into, epoxy is a great way to go. It’s non-shrinking and gap-filling, and it soaks into deep cracks, filling them up and adhering to the wood. You can mix in sawdust or various commercially available fillers, as well as tint it with dyes. This gives you plenty of options, whether you want to disguise the epoxy and make the repair less noticeable, or highlight it and turn it into a feature, depending on the look you’re going for.
I’m the owner of Benham Design Concepts, a mixed media art studio where I design and build custom furniture and other works of art using wood, glass, stone, and various metals.
In this blog, I talk about the art I create, my journey, and the things I learn along the way.