Abstract: An improved cylindrical bottom block for casting of large ingots or billets, particularly cylindrical shaped ingots, of light metals, such as aluminum and aluminum alloys, the cylindrical bottom comprising: (a) a base section having an outer diameter; (b) a centrally located circular surface forming the upper end of the base section, the circular surface positioned substantially perpendicular to the direction of casting, the circular surface forming the floor of the dish of the cylindrical bottom block which receives and cools liquid phase metal to form the butt end of an ingot, the circular surface being substantially flat and having a peripheral edge; (c) a cylindrical rim extending around the peripheral edge of the centrally located circular surface, the rim having an upper edge and an inner side wall which forms the side wall of the dish; (d) a concave transition section positioned between the peripheral edge and the lower end of the inner side wall, the concave transition section extending completely aro