Using nanoparticles to produce iridescent metallic effects on ancient ceramic objects

Nanosized materials have been often used in the past by ancient potters to realize objects characterized by shining surfaces. One of the most outstanding examples is represented by luster pottery. Luster was one of the most sophisticated technique for the decoration of majolicas during the Renaissance period. It consists of a thin metallic film containing silver, copper and other substances, like iron oxide and cinnabar, applied in a reducing atmosphere on a previously glazed ceramic. In this way, beautiful iridescent reflections of different colours (in particular gold and ruby-red) are obtained. This technique, at first developed in Iraq, was introduced in Italy from Spain. In Italy the potters of the two centres of Gubbio and Deruta (central Italy) became so expert that nowadays modern artisans are not able to reproduce the wonderful effects obtained during Renaissance. A complete characterization by means of numerous techniques (ICP-OES, ETAAS, XRD, SEM-EDX, TEM-EDX-SAED, SAXS and UV-Vis) investigating both elemental composition and surface optical properties, has been carried out an a great number of shards and precious work of arts stored in some important museums. This has allowed to draw some conclusions on the preparation technique partly disclosing the secrets of the past.