Woodworking Tips
Woodworking Tips Index
Wood Fillers
I received questions a couple weeks ago about what kind of wood fillers we use and why. The answer is there are two kinds of wood fillers -- hardening and non-hardening -- and we use both. It depends on what we need to fill and the finish we're using.

If the project is going to be stained, we fill the nail holes with non-hardening filler, such as Color Putty, after the staining and before applying the top coat. But if the project is going to be painted, then we use a hardening filler like Wood Dough (DAP) or Plastic Wood (Boyle-Midway).

NON-HARDENING FILLER. The advantage to the non-hardening filler we use is it's easy to match color. Because Color Putty comes in 17 shades, it's fairly easy to match it to a project that has been stained. And that makes the filled areas nearly invisible. And since this type of filler doesn't harden, you don't have to wait overnight to apply the topcoat of finish. Another thing we like about non-hardening filler is its long shelf life. It doesn't harden in the container. And if it gets too dry to work with, you can just add a couple drops of boiled linseed oil or mineral spirits to soften it.

HARDENING FILLER. We use hardening fillers, too. They're perfect for when we have a hole, a gap, or a knot that's too large or deep for the soft non-hardening filler. Or whenever a project is going to be painted.

When using a hardening filler, I'll fill the holes before sanding the project. Then wait overnight to allow the filler to dry, and sand the wood and filler smooth.

The biggest drawback to hardening fillers is they don't accept stain like wood does. When stained, these fillers tend to stand out from the surrounding wood. But regardless of the filler you use, it's a good idea to first test it on a piece of scrap wood that's finished the same way as your project. This way you don't get any nasty surprises.

Follow Up comments that originally appeared with Tip #16: Alan and Pamela Bohn wrote to say they use Crawford's non-shrink light-bodied spackling compound. They apply it on solid wood face frame components (especially MDF) in their cabinet and furniture business in Sandpoint, Idaho.

And Steven Zawalick of Ironwood Designs suggests we use "Bloxygen" to keep oil-based wood fillers from hardening. The inert gas in Bloxygen, he says, prevents the material from curing (www.bloxygen.com).

Go to Tip #16
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