Sanding

• Before you apply stain to the hardwood floor, you must sand it with sandpaper of varying grits. An orbital floor sander is the best tool for this job. Sand the hardwood floor three times. Start with a low 36-grit sandpaper and move on to finer grits of 80 and 100.
  
  

Sawdust

• Large amounts of sawdust will accumulate each time you sand. This sawdust can greatly interfere with the orbital sander's ability to access the hardwood. Clean sawdust from the hardwood after each sanding. You can use a broom, but a shop vacuum will prove more efficient.
  
  

Staining

• Once you've sanded the hardwood and removed all of the sawdust, you can apply stain. Liquid stains will not adequately penetrate hardwood floors. For a uniform finish, use a thick gel stain. Brush the gel onto the hardwood and then immediately wipe it away, using disposable shop rags. Don't use a synthetic paintbrush; instead, use one that has natural bristles.
  
  

Finishing

• Once the floor has dried for at least four hours, may apply the polyurethane finish. Water-based polyurethane won't bond to oil-based gel stain, so use a solvent-based polyurethane. You can brush or roll this coating onto the floor. Be sure to use either a natural bristled paintbrush or a roller equipped with a foam cover. Let the polyurethane dry for four hours before stepping onto the finished hardwood.
  
  

Warnings

• If you push the floor sander against the grain of the hardwood, splintering and other damage will occur. Always sand in the direction of the hardwood grain.