Two methods for the determination of the bulk density of granular refractory materials (grain density) having a grain size larger than 2mm are specified. Method 1 (mercury method with vacuum) is intended as a referee method. Method 2 is the arrested water absorption method. The two methods may give different results. Any statement of the value of a bilk density shall therefore be accompanied by an indication of the method used. The same method shall be used for the determination of the volume of the sample, for selecting and preparing the sample, for calculating the bulk density and for presenting the test report.