Gloss, Light Reflection and Iridescence in Ceramic Tile Enamels Containing ZrO2 and ZnO

Ceramic claddings on building facades not only present functional qualities and good resistance; they also add value to the architecture due to their qualities of light reflection, gloss and iridescence. The colour ranges produced by some enamel application techniques can vary widely. They change depending on one’s angle of vision and movement, colours in the surroundings, sunlight and their angle of incidence. In addition, the iridescent-pearl effect produced by light diffraction can lead to beautiful goniochromatic colours. This study analyses the production of square tiles of stoneware manufactured by extrusion, and their application to the Faculty of Education of the University of Alicante (FEUA) (Spain). Applying an enamel containing zirconium silicate ZrSiO4 and other metals such as Zn and Al produces iridescence-like effects. The physical-chemical properties of enamel and gloss values were characterised. A colorimetric characterisation was conducted by evaluating goniochromatic or iridescent colours, measuring the light’s spectral radiance factor, and comparing these results with other ceramic tiles of marked iridescent effects, with the presence of a final layer of anatase TiO2 enamel.