I have a lot of walnut to turn, but the few pieces I have take on a darker color than unfinished. I usually buff them a bit between coats and noticed the deep color goes away but there isn't a trace on the white clothes I use.
Where does it go and since the minwax tung oil finish i use hardens, an I doing harm to the finished coat by buffing between coats, preventing additional costs from doing what they do?

Thank you. Bill