More in Floors
Use a sander on a hardwood floor only as a last resort. Instead, use a liquid refinisher, a combination of solvents designed to dissolve old, dark finishes.
Make sure the room has adequate ventilation and to wear protective gloves. Pour the refinisher into a metal pan. Using a coarse synthetic pad and start in a corner to see how much scrubbing is required. Typically, the liquid refinisher will evaporate quickly, so you should work in small sections.
Damaged areas in the floor will look worse when the floor is re-stained. Use wood filler to fix any damage. Using a screwdriver or putty knife, mound it slightly (it shrinks as it dries) and try not to smear any onto the rest of the surface because it can alter how much stain the wood absorbs. Allow the wood filler to dry.
Sand the repairs smooth by hand, using a sanding block and a medium-grit (100 to 120) sandpaper. Vacuum the entire floor thoroughly twice. Any grit left from sanding or dirt on the floor will mar the finish.
Apply stain to bring out the grain of the wood. Don't use a stain that's too dark, as it will naturally darken over time. Following the manufacturer's instructions finish the floor with a clear finish specifically made to be used with the type of stain you applied. Alternatively, you can apply a clear finish to the wood to protect it without changing the color.