I pulled off the carpet on a staircase (carpet wrapped each stair tread completely...it's the see through type of stair case) and am staining each of the stair treads (after filling holes, sanding, and using pre-conditioning treatment). The staircase side-rails and spindles were already stained. The stain nicely matches the existing side rails and spindles. The stain on each tread looks good, EXCEPT for where the tack strip was removed....that 1 inch section on each tread isn't taking the stain very well. And they must have stained the side rails AFTER the carpet was put on each tread, because I now have to stain each side rail about 3/4 of an inch where it never had stain before...all the way around each stair tread. That section also is not taking the stain nicely (yet when I stain the rest of the side rails, it takes the stain just fine). A very talented friend of mine said that there was likely a difference in oxidation on the side rails where the carpet fibers were pressed against over 30 years. And same thing under the tack strip. So the question is, how to make it look better? I played around under a stair tread by sanding with coarse paper, treating with pre-conditioner and then sanding...but same issue occurs....just doesn't take the stain very well. Thoughts?