Appl Phys A (2010) 100: 901–910 DOI 10.1007/s00339-010-5791-0 Optical properties of lustred ceramics: complete modelling of the actual structure V. Reillon · S. Berthier · C. Andraud Received: 30 July 2009 / Accepted: 9 March 2010 / Published online: 31 July 2010 © Springer-Verlag 2010 Abstract Lustres are a kind of ceramics from the Mediter- ranean basin dating from Middle Age and Renaissance times that display astonishing colorimetric properties: their colour changes with respect to the direction under which they are observed. These properties are related with the structure containing nanoparticles of noble metal produced by the potters. In fact, various effects play a role in the aspect of these ceramics: plasmon absorption, interferences and dif- fusion. Interferences occur in the specular direction, as is commonly seen, but also in diffuse directions. In this paper, a model able to simulate these interferential effects in the diffuse directions is developed in order to understand the optical properties of the lustres. The model integrates all the phenomena mentioned above and leads to good results in re- producing the colour effects observed. The results obtained here give some clues in order to understand the reasons that may have pushed the potters to improve and control the dif- ficult process they were using at that time to produce those ceramics. V. Reillon · C. Andraud INSP, Université Pierre et Marie Curie—Paris 6, UMR 75 88, 140 rue de Lourmel, 75015 Paris, France S. Berthier ( ) INSP, Université Denis Diderot—Paris 7, UMR 75 88, 140 rue de Lourmel, 75015 Paris, France e-mail: serge.berthier@insp.jussieu.fr Fax: +33-1-44274085 V. Reillon · S. Berthier · C. Andraud INSP, CNR, UMR 75 88, 140 rue de Lourmel, 75015 Paris, France 1 Introduction Lustres are a type of ceramics produced in the Mediter- ranean basin during Middle Age and Renaissance times [1]. Their name comes from their decoration producing colour properties, which ensured the fame of these ceramics dur- ing more than a thousand years. Indeed, the aspect and the colour of lustred ceramics change with respect to the view- ing angle: in the specular direction, they display a metallic shine whereas in any other direction, mentioned in this pa- per as diffuse directions, their colour is dull and can have a completely different hue [2, 3]. These optical properties de- pend on the structure created when the potters went through the decoration process. By firing the ceramics covered with a mixture containing salts of copper and/or silver in a reduc- ing atmosphere, they managed to create a multilayer struc- ture containing silver and/or copper nanoparticles embedded in a glassy matrix, the glaze [4, 5]. In order to understand the optical properties of these ob- jects, a first model was developed including the two main optical phenomena: the plasmon absorption due to the pres- ence of the metallic nanoparticles and interferences, conse- quence of the multilayer structure [6, 7]. This model was validated by the production of similar structures as the ones observed in lustres using modern devices [7]. However, this first model presented some limitations: it did not include all the optical phenomena as it will be discussed and it was only able to simulate the reflection spectrum measured in the specular direction. To complete this model, optical measurements were per- formed on samples in order to study precisely the evolution of the colour between the specular direction and the diffuse directions [8]. An example of these measurements is dis- played on Fig. 1. The instrument used is a gonio-specto- photometer whose description can be found in other pa-