To repair scratches, you need to sand and refinish. Depending on what floor finish you have, you can gently sand the immediate area and touch it up with finish thereafter, but make sure you use the type of finish that is already there. Polyuretahne and varnish and shellac do not mix. Neither do oil and water-based polyurethane.
Sometimes, you can also hammer them out by tapping the surrounding area with a hammer until the wood surrounding the scratch is "dented" to the level of the scratch. Better yet, place a piece of metal on the area and tap that with the hammer to distrubute the blow more evenly so as to not create a new problem: hammer dents next to the scratches. Doing so requires a good touch and a bit of luck.
[This message has been edited by Lawrence (edited October 28, 2002).]
I would love to know if I can just apply a few more coats and ease the worries of ruining a new floor.
I had installed a parquet floor at the base of some stairs in my other house. We had a collie, a rather larger than normal collie at that, and a couple cats with large hind claws. They scratched the factory finish to pieces. I wound up sanding the flooring smooth and thought about something, I remember in school that the furniture we had was desks and chairs with steel feet, and yet the floors would not get scratched, so I did some looking into what was used to refinished the floors in schools and found it to be moisture cured urathane, so I gave it a try. Guess what, it worked, the marks were greatly reduced and you could hardly see any at all after 3 years of abuse.
As for removing the marks, you can try using a modelers iron, that the type used to skin radio controlled airplanes, and some water. You wet the area a bit and press the iron against the scratch and steam the dent out. It doesn't always work, but most of the lighter scratches should come up. I have done that many times to repair soft and hardwood furniture, including maple.
[This message has been edited by ACD (edited December 26, 2002).]
Applying too many layers of polyurethyne will give you a soft jelly layer in between top and bottom layers that will damage more easily from puppy paws. Usually three coats is best, sometime four, never more. I can imagine some builders doing only two, but you would notice ineven ness other than the scratches, more than likely.