Evaluating Visual Criteria for Identifying Carbon- and Iron-Based Pottery Paints from the Four Corners Region Using SEM-EDS

Abstract

AbstractPaint types on black-on-white pottery in the prehistoric American Southwest have had significance for both chronological and sociocultural interpretations. Visual attributes have formed the basis for distinguishing carbon- and mineral-based paints on ancient black-on-white pottery in the American Southwest for over 60 years. In this study, an SEM-EDS (scanning electron microscope-energy dispersive X-ray spectrometer) system was first used to make an independent objective determination of the mineral or non-mineral paint present on 15 Mesa Verde White Ware sherds. Then, a group of 19 people (including experienced archaeologists and newly trained individuals) examined and classified the paint on these sherds, achieving an overall accuracy of 84.2 percent. This group also ranked in priority order the visual attributes they felt were most useful in determining pottery paint type: nature of edges (fuzzy, sharp), absorption (soaks in, sits on top), luster (shiny, dull), color range (black-gray-blue; black-brown-reddish), flakiness (doesn't flake off, flakes off), thickness (thin, thick), and surface polish (polish striations visible through paint, striations not visible through paint). In each case, the attribute applicable to carbon-based paint is listed first. The most difficult sherds for the group to identify displayed attributes of both carbon and mineral paints. A category for "mixed" paint type, already in use by archaeologists, is a reasonable third category for labeling sherd paint, as long as it does not become a "catch-all" category. For problematic sherds, the SEM-EDS can be used to characterize paint type, then the visual attributes adjusted to improve investigator accuracy in paint type determination.