NOVELTY - The substrate mold comprises refractory materials that have a leading edge (108), a trailing edge (109) and a variable thermal mass comprising a leading edge thermal mass and a trailing edge thermal mass such that the leading edge thermal mass is less than the trailing edge thermal mass. The variable thermal mass: varies continuously from the leading edge thermal mass to the trailing edge thermal mass; comprises a step-wise gradation from the leading edge thermal mass to the trailing edge thermal mass; and is achieved in part by a variation of the porosity of the substrate mold.    USE - The substrate mold is useful for making an article of a semiconducting material (claimed), where the semiconducting material is useful: for manufacturing switching elements such as transistors in electronic devices; and in a solar cell.    ADVANTAGE - The substrate mold has improved thermophysical properties.    DETAILED DESCRIPTION - The substrate mold comprises refractory materials that have a leading edge (108), a trailing edge (109) and a variable thermal mass comprising a leading edge thermal mass and a trailing edge thermal mass such that the leading edge thermal mass is less than the trailing edge thermal mass. The variable thermal mass: varies continuously from the leading edge thermal mass to the trailing edge thermal mass; comprises a step-wise gradation from the leading edge thermal mass to the trailing edge thermal mass; and is achieved in part by a variation of the porosity of the substrate mold and achieved in part by a variation in the material composition of the substrate mold. INDEPENDENT CLAIMS are included for:    (1) a method of making an article of a semiconducting material; and    (2) a method of minimizing a total thickness variation of an unsupported article of semiconducting material.    DESCRIPTION OF DRAWING(S) - The diagrams show a schematic view of a method for making an article of semiconducting material.    External surface (102)    Semiconducting material (104)    Solidified semiconducting layer (106)    Leading edge (108)    Trailing edge. (109)