Color in ceramic glazes: analysis of pigments and opacifier grain size distribution effect by spectrophotometer

The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. In particular the pigment and opacifier grain size distribution is fundamental to determine the optical properties of the glazes directly changing the color of the product. In this work the influence of the grain size distribution of both zircon (ZrSiO4) opacifier and yellow zircon-praseodymium pigment ((Zr,Pr)SiO4) on the color developed by an opaque glaze was evaluated. The glazes were prepared by addition of zircon opacifier (three different grain size distribution) and yellow Pr-zircon pigment (before and after its micronization) to a commercial frit. The color of the glazes were measured with a spectrophotometer and the absorption and scattering properties of the obtained glazes were explained through the Kubelka-Munk model. The opacifier grain size has the major effect on the scattering of the light while the micronization of the yellow Pr-pigment do not affected significantly the reflectance and thus the color of the evaluated glazes.