The manufacture of porcelain stoneware has undergone a spectacular growth in the last years, as a result of the good technical and functional performance associated to the impervious feature of the sintered product, together with the great technological advance that the ceramic tile manufacturing sector is experiencing . To such an extent, that today, porcelain stoneware is the most
demanded product for use in flooring surfaces, but at the same time, it is becoming important to incorporate in other applications such as ventilated facades.
The lack of planarity in porcelain tiles represents a group of defects that remarkably reduce the quality of the finished product. The origin for this problem can be diverse: wrong fit between glaze and body, inadequate firing and pyroplastic deformation . Assuming an adequate firing process, the other two causes are certainly related to both materials and manufacturing process. While the curvature problem associated to the mismatch between body and glaze has extensively reported in the literature for different types of tiles , research on pyroplastic deformation phenomenon has mainly focused on whitewares products (tableware, sanitaryware, etc) ,. Despite the interesting findings reported by all this research, it should be noted that firing of whitewares is commonly carried out at much longer cycles than those used in porcelain tile manufacturing, therefore these findings are not easily extrapolable.