Technological investigation of luster decorated ancient majolicas
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Technological investigation of luster decorated ancient majolicas G. Padeletti1, P. Fermo2, S.Gilardoni2 1 Istituto di Chimica dei Materiali CNR-ICMAT, Area della Ricerca di Roma-Montelibretti, via Salaria Km 29.5, 00016 Monterotondo (Roma), Italy 2 Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Università di Milano, via Venezian 21, 20133 Milano, Italy
ABSTRACT In this work some luster decorated ancient ceramics have been analyzed in order to acquire knowledge about technological procedures in luster production during the Renaissance period in Italy. Luster is a thin decorative metallic film present on the surfaces of some previously glazed ancient majolicas. It was obtained by applying on the majolica surface a mixture containing silver and copper compounds. Subsequently the object was fired in a reducing atmosphere. It was found that the luster color, red-like or gold-like, depends not only on the chemical composition, determined by Inductively Coupled Plasma Emission Spectroscopy (ICP-OES), but on the dimensions of silver and copper metallic nanoparticles forming the luster too. Nanocrystals’ dimensions and structural characteristics were determined by Transmission Electron Microscopy (TEM). As obtaining a satisfactory luster depends on the composition of the underlying glaze too, the chemical composition of the glazes have been determined and the analytical data were submitted to statistical multivariate analysis.
INTRODUCTION New applications of nanostructured systems are now a major area of research in material science and technology due to the great potential that nanosystems offer. It is worth noting that nanophase materials were already produced in the past. To the best of our knowledge, among the most ancient ones we can consider Maya blue paint, dating at least from 8th century A.D. [1] as well as the gold ruby glasses, the Lycurgus cup [2] and luster decorated ancient majolicas which are the object of the present study. The luster technique, well known to Arabs in the 9th century spread from the Islamic world to Spain and, at last, to central Italy where it achieved its maximum splendor during Renaissance period in Gubbio and Deruta (Umbria, Italy). This kind of decoration consists of a gold or red metallic iridescent film applied on previously glazed pottery by means of a particular procedure in a reducing atmosphere at temperature around 650°C. Luster layers were obtained according to the ancient recipes [3] applying a mixture made up of silver and copper salts, iron oxide, clay and other substances on previously glazed pottery. The mixture composition varied according to the mixture composition. Generally silver and copper content were associated with gold and red colors respectively. Nowadays modern ceramists can’t obtain the wonderful shining and iridescent effects achieved in the past as luster ceramic largely fell out of use by the Renaissance period. In fact luster technique was considered mysterious because it was difficult to make good luster and furthermore the recipes were
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