Water and hardwood floors do not mix. The smallest amounts of water on a hardwood surface can cause damage. This will cause your floor to swell, bend and distort over time. Sponge mops, even if they have almost all the water squeezed out, are still going to leave small amounts. To clean a hardwood floor you should ditch the water and use specially formulated hardwood cleaning products. Steer clear of things that have soaps and waxes, this will preclude any future recoat. This includes perennial favorites, Orange Glo, Mop and Glo and Murphys Oil. Use your favorite hardwood floor cleaner and a microfiber mop.