text: According to the rule, a casting with a larger surface area and smaller volume will cool more quickly than a casting with a smaller surface area and a larger volume under otherwise comparable conditions. The relationship can be mathematically expressed as:
  Where  is the solidification time,  is the volume of the casting,  is the surface area of the casting that contacts the mold,  is a constant, and  is the mold constant. 
  This relationship can be expressed more simply as:
  Where the modulus  is the ratio of the casting's volume to its surface area:
  The mold constant  depends on the properties of the metal, such as density, heat capacity, heat of fusion and superheat, and the mold, such as initial temperature, density, thermal conductivity, heat capacity and wall thickness.