The mass (I) of the casting material is controlled. This control preferably has the mass satisfying the following formula: 0.92 x Di x Vc <= I <= 0.98 x Di x V. Di is the theoretical density in grams per cubic centimetre of the casting material, and Vc is the cavity volume in cubic centimetres. The mass of the material mass is located within a range from 93 to 97 per cent of the theoretical mass.
