Highly reflective engobes for ink-jet printed coloured porcelain stoneware tiles (CO-2:L05)

Abstract

Ink-jet decoration is a technology suitable for designing ceramic tiles with solar reflectance (SR) properties. SR is the ratio between the solar energy reflected by a surface and the total incident energy. If incorporated into the cities' building envelope, solar reflective tiles mitigate the Urban Heat Island (UHI) phenomenon, which makes urban centres hotter than rural areas. Even if many efforts have been conducted to develop solar reflective surfaces, little research has been conducted for the development of coloured tiles suitable to be fabricated by ink-jet technology, where the inks tend to counteract the effect of the reflective engobes. To overcome such an issue, the fabrication of solar reflective ink-jet decorated tiles using a reflective engobe was investigated. The engobe was prepared using an industrial CZAS (CaO–ZrO2–Al2O3–SiO2) frit and a ZrSiO4 pigment. The engobe prepared with such frit presented a high SR value (0.918 ± 0.002) and was able to develop ink-jet printed coloured tiles (cool colors) using both white and red porcelain stoneware supports. Overall, it was found that using high engobe thicknesses, white porcelain stoneware supports, and light colour inks allows the fabrication of cool color ink-jet printed tiles. Most of those tiles present solar reflective properties higher than those reported in previous works, even for dark inks that usually tend to counteract the effect of solar reflective engobes.