The campaign life of blast furnaces can be greatly limited by the interactions of carbon walls with liquid Fe-Csat. Numerous carbon forms have been investigated but not glassy carbon. In this work, liquid Fe-Csat catalyzed the graphitization of glassy carbon crucibles heated in a high-temperature confocal scanning laser microscope. Graphitization created readily wetted pores into which the hot metal penetrated, similar to the embrittlement layer seen in blast furnace hearth refractory.