Let’s face it, woodworking blemishes—dents, scratches, holes, and tear-out—happen. The trick is finding the filler that, when correctly applied, can make defects disappear.
There are dozens of different patching products, but most fall into one of three general categories: solvent-based, water-based, and two-part epoxies. Choosing the right filler depends on several factors, including drying time, the size and type of repair, and the kind of finish you intend to apply.
Solvent-based
Solvent-based fillers dry fast—most can be sanded within 15 minutes after application—and are compatible with most finishes. They’re the perfect choice when you want to fill holes, sand them flush, and then apply a finish on the same day. Solvent-based fillers shrink and crack less than their water-based counterparts. They’re also suitable for exterior use.
On the downside, solvent-based fillers don’t accept stain well. They also tend to be stiff and can be tricky to apply on larger areas. In addition to odor and flammability issues, cleanup requires a solvent—typically lacquer thinner. Because of its fast-drying ingredients, this type of filler tends to dry out in the can. Therefore, to prevent waste, buy solvent-based fillers in small quantities.
Water-based
Water-based fillers dry fairly slowly—often taking 30 to 45 minutes. The extra working time and smoother consistency mean they’re easier to tool, making them a good choice for larger repairs or those that need shaping. Once dry, they are compatible with most finishes and accept stain well. Of course, water-based fillers have no solvent odor and are nonflammable. Some you can cut with water for use as pore fillers on open-grained woods.
Water-based fillers shrink more than solvent-based and sometimes crack. With a small investment in time, you can apply a skim coat over the cracks and sand smooth.
Most water-based fillers are soft, which makes for easy sanding, but this also means that they lack structural integrity and may fail in areas that might see heavy use—like on a tool handle or along a table edge.
Premixed fillers have a longer shelf life than solvent-based, but should be protected from freezing temperatures. Powdered fillers work and perform similarly to Plaster of Paris. Setting-type putty has an indefinite shelf life, but once mixed it hardens quickly. Both types can be tinted with water-based paints and stains.
Many fillers claim to be stainable, but none accept stain exactly like the surrounding wood. For the best patch, stain the piece and then pick a filler (or stain a neutral filler) to match.
Tip Alert: Resist the urge to mix sawdust and yellow glue. The blend seldom accepts finish and can usually be spotted from across the room.
Two-part fillers
Ounce for ounce, two-part fillers cost more, but when needed, they’re worth every cent. For a paint-grade patch, epoxy putties are a good choice for rebuilding edges that will be shaped or are likely to receive wear. Liquid epoxies do well at filling knots and cracks. Neither shrinks while curing. Epoxies don’t accept stain, but you can add fine sawdust or universal pigments to obtain a perfect match. Finally, epoxy has a long shelf life, but once mixed, you must use it before it starts to cure and discard what you don’t use.
