• Nothing looks better than a newly finished hardwood floor--unless you do it badly. Floors that are oversanded, or have overly dark or splotchy stain or bubbles in the gloss are going to look bad not matter how nice the wood is. Take the time to do it right, and watch out for these common pitfalls.
  
  

Sanding Too Much

• If re-staining is part of your refinishing project, the floor will have to be sanded down to bare wood to remove the previous stain and open the pores of the wood to accept the new stain. If you sand it too deeply, though, you run the risk of exposing the tongue-and-groove milling on the edges of the boards. Use a drum sander that starts with a rough-grade paper (20 or 30 grit), which will grind off most of the stain but not all of it, thus giving you a clear indication of how deep you have to go. Then move to progressively finer paper in two or three subsequent sandings, with the final paper fine enough (120 or 150 grit) that it's not really digging down at all but just smoothing the surface. Never let the drum sander stand in one place while it's running.
  
  

Staining Too Much

• When staining, always err on the side of making the shade too light. You can always darken a stain job that is too light, but if you get it too dark, there won't be much you can do about it. Stain works by seeping into the wood, and it will continue seeping until you wipe up the excess from the top. The longer it sits before you wipe it, the darker it gets. Practice on a piece of scrap flooring to get the right shade. Start by letting it sit just 30 seconds or so, then allowing longer times, in 30-second intervals, until you arrive at the right length of time for the shade you want.
  
  

Polyurethane Issues

• Polyurethane is the preferred top-gloss for flooring today, having mostly replaced varnish, because it's more clear and shiny and dries harder. But it has some of the same drawbacks as varnish, which you need to be aware of. The formation of bubbles that dry in the finish is a major problem you can avoid by gently stirring rather than shaking the polyurethane can before application, and applying it very slowly and evenly, in thin layers. A common mistake people make is to apply the second layer of polyurethane without lightly sanding and dulling the first layer, which is necessary to prevent the gloss from flaking off later. All but the final layer should be lightly sanded after drying.