Copper speciation in lustre layers

Lustre is a metal-glass nanocomposite layer consisting of metallic silver and/or copper nanoparticles in a glass matrix, located at the outermost surface at a depth between 40 nm and 200 nm and with a thickness from ~ 100 nm to 5 µm. It was obtained by a process of ionic exchange between the alkali ions of the glass and silver and copper ions from a precursor applied to the glass surface. The concentration and distribution of these nanoparticles, as well as the presence of ionic copper and silver species, contribute to the different optical properties of the lustre layer, such as colour and gloss. The optical properties depend on the materials and the production process (technology) and provide historical information about different production centres. It is essential to analyse cross sections of the decorations by XRF and XANES with submicron resolution to determine the distribution of metallic and ionic species and to establish correlations between them and lustre technology.