Material and diagnostic characterization of 17th century mural paintings by spectra-colorimetry and SEM-EDS: An insight look at José de Escovar workshop at the CONVENT of Na Sra da Saudação (Southern Portugal)

Abstract

The early 17th century mural paintings set from the low-choir of the extinct Dominican Convent of Nossa Senhora da Saudac¸~ao in the town of Montemor-onovo were analyzed by a setup comprising visible spectra- colorimetry and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEMEDS) complemented with optical microscopy (OM), micro X-ray diffraction, micro FTIR, and micro Raman spectroscopy. The main goals were material and diagnostic characterization of the paint layers and pictorial techniques used by Jose de Escovar workshop, one of the most active and controversial easel and mural painters of Evora Archiepiscopate between 1585 and 1622. The results show a differentiate use of red, blue, and green pigments in an alkaline environment. Stable mercury sulfide (HgS) was identified in almost all red areas in the latest scenes while, in the first ones, red ochre (Fe2O3) is the predominant pigment. Faded smalt (a co-potassium silicate glass) is present pure in the sky background or mixed with red ochre in the garments at the beginning of the low-choir but less at the end. Five kinds of copperbased materials, with different degrees of color alteration, were found, namely malachite and azurite, copper chlorides, copper sulfates (e.g., posjnakite), and pseudomalachite. Another curious feature is the uneven use of a limewash made with slaked calcitic lime in the carnations. Lack of material, internal organization strategies, or technical differences within the team are probably the most likely causes.