Lead and Zinc Pigmented Mural Paint: Discovering Ancient Technologies at Lowry Pueblo Great House in Southwest Colorado

Abstract

At Lowry Pueblo, small fragments of painted plaster are all that remain of a bold white step pattern mural that once decorated Kivas A and B. We used the following analytical techniques to study these fragments: visual microscopic analysis, portable X-ray fluorescence, scanning electron microscopy with an energy dispersive X-ray spectrometer, powder X-ray diffraction, and radiocarbon dating. We identified zinc oxide and lead sulfate pigment minerals in the glossy white paint, whereas calcium carbonate was identified as the pigment for the matte white paint. Radiocarbon dating of a lead layer places mural production at 1030–1210 cal A.D., consistent with occupation at Lowry Pueblo Great House. Stratigraphic analyses of the painted plaster layers reveals that underlying glossy white paint was applied before the ultimate matte white layer. The change in pigment source and paint recipes demonstrate a design-modifying choice made by the kiva painters.

En Lowry Pueblo, pequeños fragmentos de yeso pintado son todos los restos que quedan de un mural con patrones escalonados blancos en Kivas A y B. Usamos la siguiente técnicas de análisis para estudiar estos fragmentos: análisis microscópico visual; fluorescencia de rayos X portátil; microscopia electrónica de barrido con espectroscopia de rayos X; difracción de rayos X de polvo; y fechamiento por radiocarbono. Identificamos dos pigmentos minerales, óxido de zinc y sulfato de plomo en la pintura blanca satinada, además carbonato de calcio fue identificado como el pigmento para la pintura blanca mate. Fechas de radiocarbono reportan una producción de las capas de plomo para 1030–1210 cal A.D., congruente con la ocupación de Casa Grande de Lowry Pueblo. Análisis estratigráficos de las capas de yeso pintadas revelan que la primera capa fue la blanca satinada y sobre esta se pintó la capa blanca mate, que es la última. El cambio de yacimiento para obtener el pigmento y las recetas de pinturas demostraron una selección específica hecha por los pintores de kivas.

KEYWORDS:

• Lowry Pueblo
• kiva mural
• pigment analysis
• lead paint
• portable X-ray fluorescence
• powder X-ray diffraction
• plasma oxidation
• AMS radiocarbon dating

Acknowledgements

The authors wish to offer our deepest gratitude to our archaeological collaborator Sally Cole for asking us to participate in this interesting research. This project would not have been possible without Sally’s efforts and contributions. We thank the staff at the Canyon of the Ancients Visitor Center and Museum. We are grateful to Texas A&M University – Qatar and to Mark MacKenzie, Director of Conservation Laboratory, Museum of New Mexico, Santa Fe, NM, for the use of pXRF instruments. Dr. Mohammad Yousef, Texas A&M University – Qatar assisted in SEM measurements taken there. Radiocarbon analyses were performed by Dr. Tom Guilderson at the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. XRD was performed by Dr. Joseph Riebenspies at the X-Ray Diffraction Laboratory within the Department of Chemistry at Texas A&M University. We also wish to thank three anonymous reviewers whose comments greatly improved this manuscript. While we are archaeological chemists, our knowledge of Ancestral Pueblo archaeology in the Four Corners region is limited. Any errors in this manuscript are our own.

Disclosure Statement

No potential conflict of interest was reported by the author(s).