In 1946 TAM (Taller de Arte Mural) a group of famous Argentine artists namely Castagnino, Spilimbergo, Urruchua and Colmeiro, realized the decoration of four lunettes placed above the entrances of the Galerias Pacifico in Buenos Aires. Twenty-four samples coming from these lunettes have been analyzed by means the infrared transmission micro-spectroscopy to determine the composition of the preparation layer (mainly composed by gypsum) and the nature of binder (a drying oil), while the investigation of Raman micro-spectroscopy has allowed to identify the inorganic pigments and the synthetic organic dyes present. (C) 2013 The Authors. Published by Elsevier B.V. Selection and peer-review under responsibility of the IA-CS (Italian Association of Conservation Scientists) and University of Antwerp