You've finished your woodworking project, and an unsightly blotch jumps out at you. The ugly smear is there because you didn't remove all the excess filler after you patched some nail holes or cracks. Filler tends to stain darker or lighter than natural wood. It also shows up on beams or plywood patched during manufacturing. Fortunately, you can remove filler with a few easy steps.
Although most wood filler is made of cellulose, which is wood fibers, wood filler dries harder than wood. When it's used to fill a defect, it also fills the pores of the wood, causing discoloration.
Avoid blotches in the first place by placing tape over the wood and nailing through the tape. Then add the filler with the tape in place. When you remove the tape, the filler remains only in the hole.
Don't Remove Everything
Remember that you don't want to remove all the filler from patches, gouges and holes you've made or are repairing; you only want to remove the smear. Start with a glue scraper. If that doesn't work, move on to sandpaper.
Blotch and Smear Removal
Step 1: Try Mineral Spirits
Dampen a cloth with mineral spirits. Rub the filler using a circular motion. If that doesn't remove the stain, continue to Step 2.
Step 2: Scrape It
Grasp the handle of a wood scraper. Place the sharp edge of the scraper at the far end of the filler smear. Apply pressure and pull the sharp blade of the scraper toward your body. Use a sharpened dowel for tight corners.
Move the scraper parallel with the grain only. Perpendicular movement can scratch or cut the wood.
Step 3: Repeat Scraping
Repeat Step 2 as many times as needed until you remove the raised portion of the filler smear. Dark or light tinting probably will remain; that's OK for now.
Step 4: Sand It
Place 100-grit sandpaper on a hand-sanding block. Sand back and forth over the scraped area, sanding parallel to the grain, only until the filler is removed. This should take care of any tinting problem.
Sanding previously stained areas could remove the stain along with the filler. When you use a stain, keep some on hand. Then you can wipe it over a sanded area to fill in color if needed.
Completely Remove Filler
Use sharp tools if you want to completely remove filler from holes, gouges or defects when the filler is crumbling, becomes loose or is discolored. For bigger holes, a drill/driver with a drill bit is sufficient. Smaller holes might require the use of a craft knife, utility knife or other pointed object such as the point of a compass or even a needle.
Step 1: Drill It
Insert a drill bit that's slightly smaller than the hole or defect holding the filler you want to remove. Using the slowest speed, drill out the filler.
Step 2: Dig It
Use a sharp, pointed tool to dig out the filler. Chip and pry it out of the hole. Use a needle to dig it out of larger open pores if desired.
Step 3: Sand It
Sand the area lightly with medium-grit steel wool. Wipe the area with a soft cloth saturated with mineral spirits to highlight filler you might have missed, and repeat sanding if necessary.
If you're removing filler from a finished surface, standard wood filler isn't appropriate to refill the hole. Use a putty crayon instead. You can apply it to finished surfaces, and hundreds of colors are available for a perfect match.
Floor Filler Paste
Wood floor filler is more like a soft paste, and it makes a bigger mess. It's not a good idea to clean it before it's dry, because that would pull the filler from cracks, holes and defects where you want it to remain.
Use burlap to remove floor paste filler. Because floor filler it's softer, it responds to the abrasive texture of burlap. Scrub it with authority, using both hands working parallel with the grain. If the burlap leaves a discolored area, it may be necessary to sand it, or leave it as is rather than risk a blotchy spot.
When patching or repairing defects in wood, it's wise to use a color-matched filler -- walnut filler for walnut, for example, or mahogany filler for mahogany. That should reduce the likelihood that you'll need to remove it later.