This part of ISO 12625 specifies a test method for the determination of grammage of tissue paper and tissue products. Grammage may be measured by determining the mass of a test piece or test pieces of tissue paper or tissue products cut to specified dimensions, or by determining the mass and area of a specified number of units of finished tissue products. It is expressly stated that the detection of impurities and contraries in tissue paper and tissue products should be applied according to ISO 15755. For the determination of moisture content in tissue paper and tissue products, ISO 287 should be applied.