At some point in the history of my 1940's house, there was a water problem in the basement. My guess, a water heater. Anyway, the panels in the basement in one area are stained at the bottom. I took the base molding off, and scrubbed after sanding off the finish. Then applied a paste of oxalic acid. Left if for a few hours, Then washed off the wood bleach. Tuns of yellow water. Still there's a quite dark stain. When the wood dries, if shifts to a light grey which would be ok, but not perfect. I tested a touch of shellac with a vintage amber tone to match the rest of the wall, and the stain comes out dark again. Before I give up with this and put a much taller base board on, is there something else I can use to cover the stains before finishing? Maybe some sort of paint or something?