I really want to try that, because how fucking awesome would that be. Carving a stone pipe...that's badass.
Do not use fimo or sculpey or any of the polymer clays. Polymer clays are ground plastic, PVC to be exact. Pvc when burned gives off poisonous gases.
Good point, I dont know that many people that actually put the lighter onto the pipe though. Normally the lighter doesnt even come in contact with the pipe at all, not nearly long enough to even burn it.
http://www.pcpolyzine.com/april2001/issues.html This article says its not poisonous gases... and he seems to have evidence enough for me. And how about using unfired regular clay?