The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. Furthermore is important to verify if the glaze devitrifies because the crystallized phases can contribute to the optical properties of the system. The size and the quantity of the formed crystals can change significantly the glaze color. The mean goal of this study was to evaluate the influence of firing temperature on the color stability of an opaque ceramic glaze colored by a blue vanadium-zircon pigment taking into account all the optical components. Quantitative X-ray diffraction analysis was conducted in order to evaluate the pigment dissolution at the three studied temperature and the quantity of the in situ formed zircon crystals from the used frit. The reported study demonstrated the importance to consider all the components in a multicomponent optical system as a ceramic glaze. (c) 2006 Elsevier Ltd. All rights reserved.