JOURNAL OF MATERIALS SCIENCE 36 (2 0 0 1 ) 2227 – 2236 Characterization of mural paintings from Cacaxtla M. ORTEGA-AVIL ´ ES, C. M. SAN-GERM ´ AN, D. MENDOZA-ANAYA Instituto Nacional de Investigaciones Nucleares Amsterdam 46-202, Hip ´ odromo Condesa. 06100 M ´ exico, D.F. M´ exico E-mail: ascencio@nuclear.inin.mx D. MORALES Complejo Arqueol ´ ogico Cacaxtla-Xochitecatl, Tlaxcala, INAH M. JOS ´ E-YACAM ´ AN Instituto Nacional de Investigaciones Nucleares Amsterdam 46-202, Hip ´ odromo Condesa. 06100 M ´ exico, D.F. M´ exico; Instituto de F´ısica, Universidad Nacional Aut´ onoma de M ´ exico, Apdo. Postal 20-363, Delegaci ´ on Alvaro Obreg ´ on, 01000 M ´ exico, D.F., M´ exico One of the most remarked customs of ancient mesoamerican cultures was that of record historical events by painting murals. It was used a rich variety of colours which is still visible in some mesoamerican buildings. In this work is reported the analysis by SEM, TEM, XRD, and FTIR, of the materials used to produce mural paintings of the archaeological zone of Cacaxtla M ´ exico. The results show needle-like fibers, granular aggregates and large crystalline areas. The elemental analysis reveal a substantial concentration of O, Ca and C, followed by Si, Mg, Al, Fe, and K in lower concentration. It was found the main component in the substrate is calcite. It is also relevant the presence of palygorskite in blue and green pigments, hematite in red and pink, and calcite in white. It was also possible to identify long fibers of palygorskite on whose surface there were observed nanoparticles of metallic oxides attached. C  2001 Kluwer Academic Publishers 1. Introduction The microstructural analysis performed in archaeolog- ical studies of pottery, paintings, stuccos and sculptures provides essential information about the origin of mate- rials used by ancient cultures, and give information on their technological development [1–3]. In addition, ar- chaeological materials normally suffer detriment due to environmental, biological agents and internal mechan- ical stresses. It is necessary to understand the physico- chemical properties of the archaeological materials, in order to avoid co-lateral effects after the application of any restoration method [3, 4]. This work presents the results obtained from several samples of mural paintings from the Cacaxtla archaeo- logical site located in Tlaxcala, Mexico. This important site was occupied by Olmeca-Xicalanca culture during the Epiclassic period from 700 a.c. to 900 a.c. [5, 6]. Distinct cultures like Mayan, Teotihuacans and Olmecs gave a direct influence. Such influence can be observed in their buildings, pictorial representations, pottery, and sculptures. The archaeological site of Cacaxtla has several build- ings that were decorated with mural paintings, in which, war scenes, rulers and warriors such as “eagle and jaguar knights” can be observed. Several colors includ- ing red, blue, ochre, black, brown, white and green were used to perform the murals. Their principal building named The Great Basement, discovered on the 70’s, was decorated with mural paintings associated to sev- eral architectural phases; each one elaborated with a great variety of colors [6]. Electron Microscopy Techniques have gained impor- tance in the study and analysis of archaeological mate- rials and art objects [7, 8]. These techniques have being used to obtain important data about colored materials [8–10]. In order to support experimental electron mi- croscopy results, simulation studies were performed too [14, 15]. The pigments characterization was performed us- ing different analytical techniques such as Scan- ning Electron Microscopy (SEM), Transmission Elec- tron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray Diffraction (XRD) [12–14]. A comparison of the structural and chemical composition among different paintings is included, try- ing to establish the origin of the colors. 2. Experimental methods Samples were collected directly in the archaeological site. Small fragments of paintings, each one of differ- ent color, were selected. In particular blue, red, pink, ochre, brown, white and green samples were studied. Microstructural analysis was carried out with a Scan- ning Electron Microscope, Phillips XL30 (SEM) fitted with an (EDAX) Energy X-ray Dispersive Spectrom- eter (EDS). The morphology was observed in sec- ondary electrons mode and by mixing secondary and 0022–2461 C  2001 Kluwer Academic Publishers 2227