Like the RDG model [11], the present criterion considers tensile deformation normal to columnar dendritic grains and shrinkage feeding parallel to them. However, there are several differences between the two models. First, in the RDG model the differential control volume moves and it consists of both dendrite arms and the liquid between them. In the present model, however, the differential control volume is stationary and it consists of the space at the grain boundary (and the liquid in it). This allows the presence of the grain boundary, where cracking occurs, to be dealt with explicitly. Second, in the RDG model the governing differential equation is in the form of steady-state and two-phase, while in the present model it is in the form of unsteady-state and single-phase. Third, in the RDG model a void is assumed to form to cause cracking when the liquid pressure in the mushy zone falls below a certain cavitation pressure. In the present model, however, it is when the net expansion of the intergranular space exceeds liquid feeding.