Recently I went to cook something on my cast iron pan. I turned the burner on, drizzled in some oil (I think it was olive oil) and started chopping some vegetables. When I turned back a few moments later, I found that the oil had collected in this strange star-shaped pattern. I was completely shocked until I realized that the oil seemed to be pooling on the areas where the grate below was touching the pan (compare with the unused grate visible in these photos) and in the middle directly above the burner.
That made this less mysterious, but still didn't tell me anything about why the oil would collect itself in this manner. I assume this has something to do with the temperature distribution across the surface? Maybe the pan is coolest in the center where the flames don't reach and along the grate pattern where the metal below siphons away some heat. But even if this is the case, can someone explain to me why the oil would be attracted to these areas so strongly?
