Lusters of different color and reflectivity were obtained under controlled conditions in a laboratory using medieval recipes. In this study, we analyze the influence of paint recipes, glaze compositions, and thermal paths and atmospheres on the final aspect and characteristics of the Ag/Cu nanocomposite layer formed. The colors and reflectivity of the medieval lusters were successfully reproduced using the cinnabar-containing recipes as basic luster paints. X-ray diffraction, Optical UV-Vis spectra, and microprobe chemical analysis were carried out to determine the composition and the nature and size of the nanoparticles and their relationship with their optical properties.