The disclosure relates to substrate molds with variable thermal mass. The disclosure relates to substrate molds comprising refractory materials having a leading edge and a trailing edge, wherein the substrate mold has a graded thermal mass comprising a leading edge thermal mass (Mt(lead)) and a trailing edge thermal mass (Mt(trail)), wherein Mt(lead) is less than Mt(trail). The disclosure also relates to methods of making articles of semiconducting material and methods of minimizing total thickness variation in articles of semiconducting material, said methods comprising using the molds disclosed.