Marks from sanding, staining issues and defects in the finish are all common wood floor refinishing problems. Sanding machines leave behind deep marks if not used properly, and staining the floor accentuates those marks. A streaky, rough or bubbly finish is also common with both oil and water-based clear finishes.
Sanding machines leave deep marks in a wood floor when using the wrong sandpaper. Using progressively finer sandpaper minimizes this damage. Staining a floor with deep sanding marks highlights the damage and contributes to an uneven look. Wiping on a conditioner before staining prevents uneven coloration.
Finish defects such as blisters, bubbles or streaks are common when using any clear finish. Sanding the finished floor lightly with a floor buffer and sanding screen before attempting another coat removes the defects.