Our pro installer applied too much dark stain and now the oak floor looks like black ink with no grain. We wanted dark but the sample showed the harder grain as lighter, which we liked. Now what?

If we sand it lightly or buff it, will that help? suggestions?

If you have only stained the floor and not put a sealer or clear finish on the floor, you may be able to lighten the stain color by washing it down with paint thinner. This is assuming the stain used was an oil based stain. Don't pour the thinner on the floor but instead dampen some rags and using the buffer, try buffing it off. You may want to try a test area first in a closet. If that doesn't do much, try to find some large steel wool pads (16" diameter) and buff the stain with the steel wool ( called burnishing )Sanding the floor will lighten it but not uniformly so I wouldn't recommend that unless you need to strip it down to raw wood and restain. If you use steel wool you cannot use a waterbased floor finish and must use an oil modified polyurethane. If you were planning on using a waterbased floor finish, instead of steel wool, you could try 3M's maroon in between coats buffing pads. A note about paint thinner. It smells and is somewhat flamable so use a respirator and rubber gloves and provide lots of fresh air. Turn off all pilot lights. If the thinner wash down lightens it to your satisfaction, allow a couple of days for the thinner to evaporate and the stain to dry before you start applying floor finishes. Good luck!

Thanks for the info Gary!