Jules' eyes flick over, but only briefly. It's just long enough to determine who is coming and recognize the people aren't a threat. Then he's back to his focus on the semi-glass.

"Don't get yourself too close, some of this is still pretty hot."

And he isn't good enough to keep the flames to only one area. Stuff drips or unintended sections get hot enough to start shifting. Jules doesn't want Garren to accidentally step in molten glass.