A metallized glaze, suitable for large-scale production, has been obtained starting from sepiolite-n(Cu, Fe) as a stable vector containing the metal-dispersed nanoparticles and following a conventional fast-firing fabrication route. A small fraction of black carbon (about 4 wt%) was added to the starting mixture of the glaze to avoid oxidation of Cu nanoparticles in the 500 degrees-700 degrees C temperature range. At higher temperature (700 degrees-1190 degrees C), a fraction of the oxygen dissolved in the glassy phase is consumed by the Fe degrees/Fe(2+) and Fe(2+)/Fe(3+) redox reaction. Based on ellipsometric and quantitative optical reflectance measurements, it has been proven that the presence of a minimum concentration of Cu nanoparticles (similar to 10 vol%) in the top surface glaze layer is a prerequisite to obtain an appropriate metalize glaze.