My friend made one. And she also did a presentation in speech class about clay. I asked her, in private, if it'd be okay to smoke out of a pipe made of clay. That's when she told me she had made one and she says that when they go through the burner or the kiln or whatever, that it makes it safe to smoke out of because it gets rid of impurities in the clay.

She also said what CJBHM said, "The kiln gets it hotter than a lighter ever could, so I think it'd be safe."