How to Remove Dark Stains from Wood Furniture
When liquid penetrates through wax and polish and gets into the finish (varnish, lacquer, or shellac) or even down to the wood itself, there may be tiny cracks in the wood. To reach them, you must strip the stained area of finish by using furniture stripper, oxalic acid crystals, or a two-step wood bleach or liquid laundry bleach. You also need to refinish the piece with varnish, lacquer, shellac, or urethane. And if, when you strip off the finish, you get down to bare wood, you need to restain it with a matching wood stain.
Melt the oxalic crystals in hot water.
Oxalic acid comes in crystals and can be purchased at paint stores and some pharmacies.
While the water is still hot, place the oxalic acid on the surface of the furniture.
A two-step wood bleach or liquid laundry bleach will also remove the stain. (Laundry bleach is weaker than either oxalic acid or a two-step wood bleach and, therefore, may have to be applied several times. It can be effective, however, if you want to work only in a small area.)
Let the liquid dry until it looks powdery and then rinse the area thoroughly with clear water.
Repeat if the dark stain hasn’t disappeared. Just be sure to rinse the area thoroughly between applications to get all of the dried crystals off the surface.
If you got down to bare wood, lightly sand the surface with fine sandpaper.
Wipe the surface with a tack-cloth to clean up all loose particles.
You can purchase tack-cloths at stores that sell paint, hardware, or do-it-yourself supplies. If all small particles haven’t been removed, the surface will be marred and you’ll be able to feel small bumps after the finish dries.
Apply a light coat of stain that matches the stain on your furniture.
Let it dry. If the color doesn’t match the furniture, repeat the steps until the color looks right.