Effect of the green porous texture on porcelain tile properties

Abstract

Porcelain tile is a product characterised by low water absorption (usually less than 0.1%) and excellent mechanical properties. To enhance tile aesthetic qualities, much of the porcelain tile production is polished to provide a high-gloss surface finish, in which certain closed pores in the tile body become visible. This apparent porosity of the polished tile, which had been closed porosity before polishing, sometimes lowers the product's stain resistance. Test pieces were formed from a porcelain tile composition prepared under different milling conditions, pressing variables being kept constant, and the pore size distribution of these pieces was determined. The effect of the porous texture of the green pieces on the evolution of porosity during sintering and on the residual porosity of the densified body was analysed. It was verified that the porous texture of the fired piece was conditioned by the porosity and size of the largest pores in the green piece. The effect of residual porosity on stain resistance was determined by two cleaning methods. The presence of large pores in the green body, stemming from insufficient milling of the raw materials mixture, led to tiles with greater residual porosity and worse stain resistance.