The ceramic vessels known as Zapotec or Oaxacan urns are among the most recognizable and significant products of the Zapotec culture, which flourished in the Valley of Oaxaca Mexico from A.D. 200 – 800. There are hundreds of these objects in museum collections throughout the world and they have been published widely, however, beyond authentification studies, scant technological information about these important artifacts has appeared in the literature.
The American Museum of Natural History holds one of the largest collections of urns outside of Mexico, including many excavated in 1898 at Xoxocotlán. This material offered a unique opportunity to undertake a technological study of an important collection of well-provenanced urns together with other artifacts from the same excavations. The study focused primarily on the painted surfaces of the urns. It appears that almost all Zapotec urns were at least partially painted, however, this aspect of the urns has not previously received a great deal of attention.
For the study, the surfaces of the urns were carefully examined and diagramed using a binocular microscope. Paint samples were taken from the urns and other related material for analysis. The pigments were identified using microchemical tests, polarized light microscopy (PLM), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). A few larger samples were taken for examination of the paint layers in cross-section.
The study revealed designs and patterns painted on these urns that are not readily apparent and could be easily overlooked without careful examination. The study also showed evidence of repainting and reuse of the urns. The analysis resulted in the positive identification of the important pigment Mayan Blue on Zapotec artifacts and an interesting pattern in the use of red pigments (cinnabar and iron oxides) on the artifacts sampled.