I'm using softie bits on my pipes. Recently, I got me an estate pipe, which was much oxidized. I got all the oxidation cleaned, and pot a softie on her. After a few smokes I noticed that under the softie the oxidation returned, but only under the softie. Does anyone know what the reason is for it? Could it be because of the saliva that gathers under the softie? does anyone know Other reasons for that? Should I stop using softie on that pipe?