When hardwood floors are newly placed, and also when they have been newly refinished, the hardwood surface is covered with a durable polyurethane coating that protects the wood from liquid spills, abrasive dirt and wear from normal family normal family foot traffic. This polyurethane coating includes tiny slivers of aluminum oxide that further increases its ability to resist damage from the UV rays contained in direct sunlight that enters the room. It also increases the luster and brilliance of the hardwood flooring.
Sand and dirt brought inside on people’s shoes, or pet’s paws, are much like sandpaper in that they will slowly scrape down the hardwood surface coating. Once the coating wears away enough, soil and spilled liquids can soak down into the wood itself, resulting in swelling, warping and even some loss of color. The UV rays from sunlight may also ‘bleach out’ or fade some of the rich colors from hardwood floors, and make them look dull and lifeless.