By chance are you using
By chance are you using “thin fire” paper? I had similar problems for a long time, and was so frustrated, I stopped grinding, and couldn’t make pieces like I wanted to. I talked with a fellow fuser recently, who told me that something with the thin fire leaves that white ring wound the edges that were touched by the grinder. I went back to using kilnwash and I haven’t had the problem since & I am back to fusing all the time!