If the freezing ratio equal to (casting area/casting volume) / (riser area/riser volume) & the volumetric ratio equal to riser volume/casting volume, for a disc casting of 20cm diameter and 10 cm thick are 1.4 and 0.8 respectively. The corresponding values for a square disc of 20cm side and 10cm thick if the same cylindrical riser with a height to diameter ratio of unity is used in both cases.