The buffing wheels on my Beall Wood Buff System turned very dark after using them on a piece of Ebony wood. While attempting to clean them using 60 grit sandpaper I noticed a lot of old compound sticking to it. After a few passes the wheels were almost white again and without the stiffness from built up compound. The tripoli accumulated the most build up and took about 3 strips of sandpaper to finish the job. Now the wheels are almost the way they were new.