Identification of the majolica polychromatic decoration by IRFC methodology

Abstract

A multi-analytical approach was applied to study majolica fragments coming from the Medieval and Renaissance waste shaft (butto) of the Monks' Palace in Capena (formerly Leprignano) in order to test the efficacy of IRFC reflectography to characterize ceramic glazed decorations. A total of 21 pottery samples dating back from 14th to 18th century were analyzed. The majority of fragments referred to Archaic and Renaissance artifacts, but one sherd of painted XVIII century majolica from Albissola has been also analyzed. The chemical composition of the colored layers was ascertained by portable surface XRF, and SEM-EDS analyses performed on freshly cut cross sections. The glazes are variable in thickness and generally composed of silicate materials, to which lead and tin compounds, respectively acting as fluxing and opacifying agents, were added. Analyzing the painted layers allowed identifying the elements responsible of the coloration. Manganese in different concentration has been found in violet, brown and black decorations, while copper was detected in the green and turquoise ones. Cobalt is the main chromophore in blue decorations, and refers to the zaffera, whose arsenic content is related to the production period. Yellow and orange decorations are due to lead antimoniate, to which iron oxides are added in the case of orange-brown decoration. Comparing the obtained analytical data with the mineral composition ascertained by micro-Raman technique gave the possibility to precisely identify all used chromophore. The precise knowledge of the composition of all painted decorations made it possible to interpret the response obtained by IRFC reflectography and couple each false color to the peculiar chromophore. The IRFC methodology was proved to be very efficient to identify the single chromophore even in the case of mixtures of pigments. It is also an alternative non-destructive, and low cost methodology that may be successfully applied to the study of decorated majolica pottery.