We recently had an inquiry asking if more finish can be added to an old site finished floor to improve its appearance. This is what we used to call a buff and coat. Recoating will not remove deep scratches or discoloration in the antique wood, but is a good choice in many cases where the finish is sound and not overly worn. The surface of the existing finish is abraded lightly to get it ready for additional finish. If there are contaminates on the wood floor such as wax, dusting products, polish, etc. the new coat may not adhere in some spots and total resanding may be a better choice. The major water based finish manufacturers make pretreatment products which aid adhesion. The water based finishes are easy to use if you know what you are doing and are used by many professionals. If you are doing the work yourself many first time attempts do not come out as well with these products. You might consider using a more traditional urethane floor finish with a slower drying time. Once you get everything cleaned up and ready two coats often looks better than one on an old floor. A finish with a low gloss level tends to help surface imperfections blend in. If you are not going to use water borne finish the old way to abrade it was to rub the surface with fine steel wool. Go with the grain of the wood floor. It is a good idea to test the compatibility of the finish you are using with the existing finish in a small out of the way area before doing the whole floor. Also the National Wood Flooring Association http://www.woodfloors.org/ has information on finishes and maintenance. Especially with antique wood, you can find small ways to improve any damage or discoloration that has happened over time, because much antique wood already carries natural imperfections!