If it's a solid rubber stem, as opposed to vulcanized rubber, you need to be careful. Solvents that are fine for vulcanite can cause hard rubber to "ripple". Oxyclean bath is fine for cleaning and only very fine grit micro-mesh for polishing. The micro-mesh needs to be used with a very light touch and very slow so you don't build heat as this will ripple the rubber as well. I would stay away from alcohol or any other solvent when cleaning these. And yes, they are fine for smoking. I have a couple of hard rubber stems on some very old pipes and they smoke fine. Just need a little extra care when preforming maintenance.