I've been thinking about this for years. When I was 8 I saw a movie that terrified me, and this is the only scene I can remember: this woman who's spinning clay on a potter's wheel, and for reasons unknown she begins to turn into plaster, from her toes to her knees and up. She starts slamming her knees with her fists but it's no use and she's completely encased in the stuff and becomes a statue.

It could be a TV show, made for TV movie, I have no idea.

Any ideas?