“Fractional distillation just popped into my old brain.”
Yep... Or different grease “drop off” tempts... Some fancy “Sticky high temp” greases will burn up bearings when temps get cold. If they do not get liquid enough to drop off you have a serious problem.
So in the same concept you can separate metals with temps where one melts but the other doesn’t yet.
Is that similar to the cones used in pottery ovens?