Microanalytical characterization of decorations in handmade ancient floor tiles using inductively coupled plasma optical emission spectrometry (ICP-OES).

Abstract

In this study a total of 114 glazed decorations of 42 ceramic floor tiles, manufactured in Sicily fromthe 16th to 19 the 21th AD, were investigated. The micro sampling method, proposed by us, using a cotton swab soaked in hydrofluoric acid, includes advantages of high sensitivity, high selectivity, simplicity, speed, not expensive and can be considered non-destructive because the point of sampling remains invisible to the human eye. ICP-OES technique was used in this study. Twenty-four elements (Al, As, B, Be, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, Pb, Sb, Se, Si, Sn, Ti, V and Zn) were determined in each colored enamel. Enameled decorations in Sicilian tiles were varied in tones and chromatic effects, obtained with a limited 25 number compounds of cobalt, copper, iron, manganese, tin, and in the artifacts following the year 1920, also titanium. An important remark is that some of the colors, such as black, orange, purple and brown were prepared using the same metals, while white, light blue, blue and green were obtained with different elements. The adoption of different recipes for the same color suggests the presence of several laboratories of ceramists working in Sicily who had preferences for different methods for the production of their enameled artifacts. Concerning the opacifier, the high amounts of lead and antimony, only in a case, indicate the use of lead antimonate (Pb2Sb2O7). Black decorations were present in several of the analyzed samples and in most of them were identified mixtures of black iron and manganese oxides. The green decorations appear to have been prepared with copper oxide; lighter hue samples contained additional amounts of zinc and/ or barium compounds. Considering all the samples, meanly, iron predominates in yellow decorations, only a sample contains large amounts of Cd, Zn and very little Sb, which suggests the use of the pigments ZnO as white) and CdS as cadmium yellow. For all samples, except one, we can exclude the use of pigments containing chromium.