excerpt from Dr Jones' paper regarding experiment performed:
http://www.physics.byu.edu/research/energy/htm7.html


We also noted that while a steel pan holding the aluminum glowed red and
then yellow hot, the molten aluminum inside retained its silvery-gray
color, adding significantly to the evidence that the yellow-white molten
metal dripping from the South Tower shortly before its collapse was NOT
molten aluminum. (Recall also that the yellow color of the molten metal
(video clip above) implies a temperature of approximately 1100 oC -- too
high for the dark-smoke hydrocarbon fires burning in the building.) This
is point worth emphasizing: aluminum has low emissivity and high
reflectivity, so that in daylight conditions molten aluminum will appear
silvery-gray, while molten iron (with its characteristic high emissivity)
will appear yellow-white (at ~1100 oC) as observed in the molten metal
dirpping from the South Tower just before its collapse