An Organic Colorant used in Painted Ancient Maya Architectural Sculpture at Nakbe, Peten, Guatemala
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ABSTRACT The ancient Lowland Maya are generally considered to have used a limited number of inorganic colorants in their polychrome reliefs due to the lack or inaccessibility of mineral resources, especially during the Late Preclassic period (300 B.C. - 300 A.D.). A notable exception is the manufacture of a blue pigment from indigo and specific types of clay, known as Maya blue, from the Classic Period (300 - 900 A.D.) through Colonial times. Another exception is a recently analyzed cream (or reddish-yellow) colored paint found on exceptionally large architectural polychrome stuccoed sculpture dating to the early Late Preclassic at the site of Nakbe, Petdn, Guatemala. The cream paint layer exhibits a dramatic peach-colored fluorescence upon exposure to ultraviolet light. An organic material, extracted with organic solvents from the acid hydrolyzed lime-based plaster surface, was characterized by means of visible light microspectroscopy, FT-IR microspectroscopy and three-dimensional fluorescence spectroscopy. Analysis of the spectra obtained from the cream colorant and comparison with spectra of reference organic materials suggests that anthraquinone derivatives may be responsible for the color, and that these compounds are similar to some of those present in organic red dyes. The cream paint was applied as a single layer with good hiding power overlying the stucco ground. The cream paint is of the same thickness (averaging 15 microns) as the only other paint present on the sculpture, a red paint pigmented with red iron oxide. The presence of organic colorants on exposed architectural features raises particular preservation problems in relation to the increased possibility and rate of deterioration due to environmental exposure of this type of organic colorant in comparison with most inorganic colorants.
INTRODUCTION This paper reports preliminary findings on the painting techniques and materials used in the production of a large mask, or "grotesque" face with an exaggerated upper lip or snoutlike projection flanked by earspool panels. The whole image has dimensions of approximately 6 x 12 meters, and is one of two masks flanking the central stairway of the pyramid designated Structure I at Nakbe, Petdn, Guatemala, dated to the Preclassic period (see Hansen, Rodriguez-Navarro and Hansen, this volume). Of particular importance is the presence of an unusual organic colorant used in one of the two reddish hued paints, a yellowish-red or "cream." The cream paint is highly fluorescent when exposed to ultraviolet light, and the data, cited below, indicate that an organic compound (or mixture of compounds) is indeed the paint colorant. The inorganic red paint colorant was more easily and straightfowardly identified as red iron oxide. Freidel [1] has reviewed the color palettes known to be used in Lowland Maya Preclassic polychrome facades. These include red and unpainted stucco (white) on Structure E-VII-Sub. at Uaxactun; red, black, and pink on a cream ground on Structure 5D-Sub. I-Ist in the North Acropolis, Tikal; and
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