Spectroscopy study of mural paintings from the Pyrenean Church of Saint Eulalia of Unha

A series of wall paintings dating from the Romanesque period to the 16th century were uncovered during restoration projects at the church of Santa Eulalia of Unha in the Val d'Aran. This study centres on the use of complementary spectroscopic techniques to examine comprehensively the pigments, binders and other materials associated with these mural paintings. These include Raman microscopy, far and mid-Fourier transform infrared (FTIR) spectroscopy both with synchrotron radiation (SR), as well as optical microscopy and scanning electron microscopy (SEM-EDS), and build upon earlier SR-X-ray diffraction studies. Traditional materials such as hematite, goethite, vermilion, red lead, carbon black and calcite were identified, but the artists' palette varied with the period. The blue pigment identified in the Romanesque frescoes was determined to be aerinite, a rare Fe(II)/Fe(III)-containing aluminosilicate found locally in the Pyrenees region. Electronic, Raman and far-SR-FTIR spectra of this pigment are presented for the first time in the context of a work of art. The presence of some nitrates, sulphates and oxalates found in the mural paintings is commented upon. Copyright (C) 2010 John Wiley & Sons, Ltd.