a b s t r a c t
The technological characteristics of porcelain stoneware tiles make them suitable for a wide range of
applications spanning far beyond traditional uses. Due to the high density, porcelain stoneware tiles
show high bending strength, wear resistance, surface hardness, and high fracture toughness. Nevertheless,
despite being usually claimed as stain resistant, the surface porosity renders porcelain stoneware
tiles vulnerable to dirt penetration with the formation of stains that can be very difficult to remove.
In the present work, we report an innovative and versatile method to realize stain resistant porcelain
stoneware tiles. The tile surface is treated by mixtures of nanosized zirconium hydroxide and nano- and
micron-sized glass frits that thanks to the low particle dimension are able to penetrate inside the surface
pores. The firing step leads to the formation of a glass matrix that can partially or totally close the surface
porosity. As a result, the fired tiles become permanently stain resistant still preserving the original esthetical
qualities of the original material. Treated tiles also show a remarkably enhanced hardness due to the
inclusion of zirconium compounds in the glass coating.