Two sets of oak stairs have been damaged by water leaking in the house during constructions. The stains are dark. We have been using oxalic acid with some success in lightening the color. Can they just be sanded. Is there a better bleach? Or a better technique to return the stairs to pre-stained condition?
Water on oak by itself doesn’t cause a dark stain, what you have there is a reaction with steel + water, probably with the steel nails or screws which fasten the stair treads.
Oxalic acid should do the trick OK .