Color prediction with simplified Kubelka-Munk model in glazes containing Fe2O3-ZrSiO4 coral pink pigments

The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. In particular in opaque glazes the crystallized phases can contribute to the optical properties of the system and then to cause changes in the color of the products. In this study the prediction of the color of coral glazes obtained by addition of hematite-zircon pigment (Fe2O3eZrSiO4) in an opaque glaze was carried out with the KubelkaeMunk model. Subsequent to the physical and chemical characterization of the glaze components (frit, opacifier and pigments), the color prediction was performed with the simplified KubelkaeMunk model proposed for zircon pigments. In particular was verified if this model is also valid in the case of pigment Fe2O3eZrSiO4 where the hematite is encapsulated by the zircon structure. Three glazes were prepared to determine the absorption optical constants from the reflectance curves measured with a spectrophotometer. The results obtained with the simplified model were in good agreement with the experimental reflectance curves and the prediction of coral color was possible with a reduced number of experiments.