Rock Art Research

Vol. 25 No. 2 (2008)
Published : Nov 18, 2008

CHARACTERISATION OF MATERIALS AND TECHNIQUES USED IN MEXICAN ROCK PAINTINGS

Benjamin Valdez (1), Juan Cobo (2), Michael Schorr (3), Roumen Zlatev (4), Leonel Cota (5)

(1) Department of Materials, Minerals and Corrosion Chemical Engineering Area, Institute of Engineering, Universidad Autonoma de Baja California Mexicali, B.C. Mexico
(2) Department of Materials, Minerals and Corrosion Chemical Engineering Area, Institute of Engineering, Universidad Autonoma de Baja California Mexicali, B.C. Mexico
(3) Department of Materials, Minerals and Corrosion Chemical Engineering Area, Institute of Engineering, Universidad Autonoma de Baja California Mexicali, B.C. Mexico
(4) Department of Materials, Minerals and Corrosion Chemical Engineering Area, Institute of Engineering, Universidad Autonoma de Baja California Mexicali, B.C. Mexico
(5) Centro de Ciencias, de la Materia Condensada, UNAM Ensenada B.C. Mexico
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Abstract

The aim of this investigation was to determine the physicochemical characteristics, the microstructure and texture of the polychrome paintings found on rocks encountered in the mountainous, arid zones of Baja California, Mexico. Tiny painting samples were collected
and analysed by SEM, EDS and FTIR techniques. The painters used four main colours: red, black, yellow and white. The paint raw materials are mostly mineral pigments: kaolin, calcite and gypsum for white; hematite for red; ochre or limonite for yellow; and charcoal from burnt wood or calcined bones for black. These are all encountered in the painters’ habitat, and water was used as a diluent and/or binder. The dry paint, of 100% solids, has been converted into a dense, hard layer, embedded into the grainy, rough, porous granite rock surface. The analysis of the paint composition permits inferences about the techniques used by the ancient painters, which can be now applied for restoration and preservation of this important cultural heritage.