Not long ago I went thorough hell and high waters when I was removing an oxidation on ebonite stem, nothing seemed to help, tried this all,micromesh pads, sanding papers, Pfeifen Kopf paste,soaking in bleach,and I thought I can get rid of this oxidation no way, but finally the solution was found, Dremel drill with polishing pads combined with white diamond paste and finished with carnauba,(spent five hours struggling with that stem, oh I hate them vulcanite stems ,