Hence my PS warning Mike! I can't recall ever giving a public knapping demo when someone didn't ask me about the hot rocks and water thing. I wonder how that story ever got started? It sure spread wide and far. Guess it sounds better than the truth.
UPDATE: I found an article by a fellow named Dan Long that may answer the question of how the story of dropping cold water on hot rocks started. Dan writes, "All I knew for sure was that it wasn't done with fire and water, a theory popularized by Edgar Rice Burroughs “Tarzan”, in which he had the hero shape a stone blade by heating it and strategically applying drops of cold water to the hot rock to remove flakes (incidentally, a great way to put out an eye!)."
Tarzan - LOL! But where did Rice Burroughs come up with his idea?