Deterioration of Pre-Hispanic Stucco Masks from the Archaeological Mayan Site of Edzná, Campeche, México

This contribution shows the results of a study carried out in order to determinate the deterioration mechanisms suffered by stucco masks from the important archaeological Mayan site of Edzna, Campeche, Mexico; due to their long exposition to the tropical environment of the zone. Stratigraphic analysis of fragments from the masks containing pigments and surface neoformation products, were analyzed by optical microscopy and scanning electron microscopy coupled to a secondary X-ray emission system. Crystalized salts mineral composition were characterized by X-ray diffraction. Also, during the study, environmental parameter like temperature and relative humidity were monitored in site. Results indicate that stuccos mineral matrix is formed by calcareous materials, covered by films with variable proportions of ferrous materials (red, ochre and yellow colors) and rich carbon content (black color). Compounds were associated to blue and green colors. Al these materials showed a high level of deterioration because of differential forces caused by stucco and deposits of environmental soluble salts during dissolution crystallization cycles caused by humidity differences between stucco and environmental as a consequence of their particular exposure conditions.