Ted Stanley wrapped up the Book and Paper Group sessions on Friday, May 11, with his presentation about the authentication and analysis of a 16th-century Mesoamerican map belonging to Princeton University Library. The map was believed to have a c. 1550 creation date, and depicts a portion of the central valley of Mexico at the time of the European conquest. Stanley attempted to determine the authenticity of the deerskin map through noninvasive analysis techniques, including light microscopy, UV-induced visible fluorescence, UV-VIS spectroscopy, and FTIR.
The map, which features black, blue, green, red, and yellow colorants on a leather support, depicts the upheaval in Mexico at the time of European conquest. Hernan Cortes famously invaded Mexico in 1519. The priests who followed in his train destroyed Maya and Aztec maps and codices, and Spanish conquistadors killed many indigenous people, especially those who resisted conversion to Christianity. In one of the map’s illustrations, priests preach to native noblemen, perhaps with limited success: one priest is shaking an Aztec listener so violently that blood flies from his nose. The map also illustrates roads, waterways, villages, agave plantations, and irrigation systems, accompanied by Aztec glyphs or pictograms and their Spanish translations, or glosses. It captures the meeting of the Old and New Worlds, with depictions of Aztec warriors, Spanish priests, Aztec shrine altars, and colonial Spanish villages. But is it authentic?
According to Stanley, the hide support was roughly scraped as part of the tanning process; he is still investigating how the Aztecs may have treated the skin to preserve it. Large, circular voids in the leather appear to be the natural result of abscesses in the animal’s skin rather than later damage. The map was previously folded and has prominent creases as a result. Its pigments are stable, with minor abrasion, and the map displays some liquid staining and minor losses along the edges.
Since no follicle pattern could be determined using light microscopy, Stanley compared the collagen fibers present in the map’s support with those of a known deerskin, and found they had comparable length and width. He also examined the map’s colorants and found evidence for both yellow and orange dyes, which were absorbed into the collagen fibers, and for blue, green, and black pigments, which were deposited on the leather surface.
Stanley then used UV fluorescence for general pigment identification, comparing the fluorescence of the map’s colorants to the fluorescence of Kremer pigment samples. Based on his observations, he tentatively identified the red colorant as cochineal, the yellow-orange as gamboge, and the blue as Maya blue, a combination of indigo and palygorskite clay. While cochineal and Maya blue are both associated with traditional Aztec culture, the gamboge was a surprise, since it is normally associated with Southeast Asia. In addition, the fluorescence of the green pigment did not match that of any Kremer samples. UV-VIS spectroscopy of the map’s colorants reinforced Stanley’s original pigment identifications, but the green remained a mystery.
Finally, Stanley turned to Fourier-Transform Infrared Spectroscopy using Attenuated Total Reflectance (FTIR-ATR) for more definitive pigment identification. Once the bands for the hide support had been subtracted, the spectrum for the red dye displayed the characteristic absorption band for carminic acid, confirming the presence of cochineal. The yellow-orange dye produced an absorption band for gambogic acid. Stanley theorizes that the gamboge present in the map is actually American gamboge, a resin that is chemically identical to Asian gamboge but originates in a Mexican plant. Both the blue and green pigments produced spectra containing absorption bands for indigo and palygorskite clays, suggesting that they are Maya blue and Maya green: the same pigment/dye complex at lower and higher pH levels, respectively. The black pigment produced absorption bands for calcium and phosphate, indicating the use of bone black.
Because all of this evidence points to the use of pigments and dyes known to have been used during the early colonial period, Stanley has determined that the map is likely to be contemporary with the European conquest of Mexico. However, the colorants, the skin, and the tanning process all provide tantalizing opportunities for further research. Could the green colorant be Maya blue in combination with a yellow dye? Is the leather in fact deerskin? How was it tanned? Finding the answers to these questions could shed more light on the map’s authenticity, and illuminate a period of dramatic historical change with even more accuracy.