Based on chemical analysis of the residue on the steel beams from the 3 collapsed WTC buildings, a physics professor has identified the material as Thermate. Thermate is the controlled demolition explosive thermite plus sulfur. Sulfur causes the thermite to burn hotter, cutting steel quickly and leaving trails of yellow colored residue. The intense heat of over 1200 degreed F can remain for several weeks. These are unique characteristics of a thermate reaction.