This part of ISO 10545 specifies methods for determining water absorption, apparent porosity, apparent relative density and bulk density of ceramic tiles.There are two methods of obtaining impregnation with water of the samples' open pores: boiling and immersion under vacuum. Boiling will impregnate open pores that are easily fillable; the vacuum method fills almost all the open pores.The boiling method shall be used for classification of tiles and product specifications. The vacuum method shall be used for apparent porosity, apparent relative density and water absorption for purposes other that classification.