In manufacturing practice, the relative fluidity of a certain metal casting melt can be quantified by the use of a spiral mold. The geometry of the spiral mold acts to limit the flow of liquid metal through the length of its spiral cavity. The more fluidity possessed by the molten metal, the farther into the spiral it will be able to flow before hardening. The maximum point the metal reaches upon the casting's solidification may be indexed as that melts relative fluidity.