Publications on Preservation
Poster Sessions
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Caitlin O'Grady, Kacy Hollenback and Christopher Roos
Society for American Archaeology Annual Meeting - Vancouver, B.C.
April 2008
Abstract
Archaeological interest in the earliest ceramics in the Southwest US has focused attention on an apparent pan-Southwestern brownware tradition. These ceramics were presumably made with readily available, self-tempered, secondary clays. Such clays abound in alluvial deposits and soils and are often enriched with organic matter. This study expands upon previous work by Roos (2005), which focused on Cienega Phase (Late Archaic) ceramics made from low-fired, alluvial muds. He suggested that these low-fired ceramics may have had toughness performance characteristics which were better than high-fired ceramics made from the same materials. In this study, we evaluate this hypothesis with a larger sample of a wider variety of alluvial muds and soils from the Mogollon Rim region. Clay sources are characterized to determine clay content, organic matter and particle distribution. Micro-chemical spot tests and portable X-Ray Fluorescence were used to chemically characterize clays. For this pilot study, four clays were selected based on their physical and chemical properties. Controlling for firing temperature and organic matter content, we use the three-point bend test for tensile strength to explore the relationship between the combustion of organic carbon and fracture resistance. Future research will utilize FTIR spectrometry and scanning electron microscopy to observe changes in the chemical and structural properties of mud organic carbon content. Finally, we explore the consequences of low-fired, organic, self-tempered clays for the formation of the earliest ceramic assemblages in the Mogollon Rim region.
Patterns of Adhesive Use in Prehistoric and Modern Repairs of Southwestern Pottery at the Arizona State Museum
Chris White, Dr. Nancy Odegaard
Canadian Conservation Institute (CCI) Conference - Preserving Aboriginal Heritage: Technical and Traditional Approaches.
September 24–28, 2007
Abstract:
A variety of materials and methods have been used to preserve ceramic vessels. Many have proven successful while others damaging. The pottery collection at the Arizona State Museum (ASM) includes a range of adhesives and coatings from modern conservation materials to original period-of-use repairs in ancient vessels. The Southwest collection comprises approximately 20,000 whole vessels, spans nearly 2000 years and encompasses all the major cultures and historical periods. The collection has been officially designated a “Save Americas Treasure” in 2000 and an Arizona State Treasure in 2006. Nearly 5000 vessels are repaired or retain a visible adhesive or coating. Adhesives were used by Native American groups, archaeologists, conservators, and others. Conservation staff have identified these adhesives and can establish a profile of the collection’s treatment history that provides a valuable tool for conservators, researchers and curators.
Assessing Mechanisms of Granite Decomposition
Caitlin O'Grady
Second Archaeological Sciences of the Americas Symposium - University of Arizona, Tucson, AZ
September 14–17, 2006
Problem
- Granite grave markers in the Southwest show rapid deterioration (over 6 to 12 months)
- Damage thought to be due to hard water used in cemetery irrigation
Project
- Granite from Fort Morgan Cemetery, CO analyzed to characterize decomposition
- Irrigation water used in cemetery maintenance analyzed for composition
Oddy Test: Testing Construction Materials for the Pottery
Vault, the Interpretive Gallery and the New Conservation Lab
Sonya Issaeva, Dr. Nancy Odegaard
American Institute for Conservation (AIC) Conference - Providence, Rhode Island
June 16–19, 2006
The Oddy Test Determines how reactive a certain material is and whether it off-gases acidic or basic fumes. These fumes can cause damage to artifacts. At the Arizona State Museum Conservation Lab the Oddy Test was performed on all building materials used for construction of the Pottery Vault, interpretive gallery and the new conservation facility. It was important to ensure that the materials used in construction were chemically stable and would not compromise the long-term preservation of the Southwest Pottery Collection. The following poster is a summary of a portion of the work that was undertaken during the construction of the Pottery Vault areas.
Abstract:
A variety of materials and methods have been used to preserve ceramic vessels. Many have proven successful while others damaging. The pottery collection at the Arizona State Museum (ASM) includes a range of adhesives and coatings from modern conservation materials to original period-of-use repairs in ancient vessels. The Southwest collection comprises approximately 20,000 whole vessels, spans nearly 2000 years and encompasses all the major cultures and historical periods. The collection has been officially designated a “Save Americas Treasure” in 2000 and an Arizona State Treasure in 2006. Nearly 5000 vessels are repaired or retain a visible adhesive or coating. Adhesives were used by Native American groups, archaeologists, conservators, and others. Conservation staff have identified these adhesives and can establish a profile of the collection’s treatment.
Reconstruction of Sikyatki Polychrome Manufacturing Technology
Caitlin O'Grady
American Institute for Conservation (AIC) Conference - Minneapolis, Minnesota
June 8–13, 2005
Abstract
There are few high-fired pottery types excavated from archaeological sites in the American Southwest. Beginning in the 14th c. AD, Hopi potters introduced two yellow
wares fired at much higher temperatures than those achieved previously. Sikyatki Polychrome, dating between AD 1350/75–1630, is an example of Hopi yellow
ware utilizing this highly developed coal-fire technology. Excavated samples are well-preserved and abundant. The type is typified by fine pale ivory paste with little
or no visible added temper. Nineteenth century ethnographic accounts suggest that potters ground low-fired clay plaques and added it to the unfired clay as temper
(Wade & McChesney 1980).
Beginning in the late 1800s and continuing to the present, modern Hopi have revived several ancient pottery traditions including Sikyatki Polychrome. However, reproduction
of the rich and even Sikyatki yellow surface colors has been inconsistent and further analysis is needed to replicate the manufacturing technology. Researchers
have suggested that the yellow surface color is the result of high firing temperature, as well as the chemical reaction of burning coal with the prepared clay
(Hack 1942b; Shepard 1968, 1971; Powers 1976; Canouts & Bishop 1994, 2003). Petrographic and chemical (SEM-EDS, FESEM-EDS and PIXE) analyses were conducted
on archaeological samples in order to test this hypothesis and reconstruct the ceramic technology. Further investigations will include collection of materials
from known ancient Hopi clay sources and replication firing studies.
Manganese Dioxide Accretions: Morphological and Analytical Investigations of Accretions on Mexican
Archaeological Ceramics
Caitlin O’Grady
American Institute for Conservation (AIC) Conference - Portland, Oregon
June 9–14, 2004
Abstract
Manganese dioxide accretions—small, irregular dark surface deposits—occur on a variety of substrates including stone, ceramic, glass and bone in diverse environments. Due to their
distinctive physical appearance, this surface phenomenon has been used as a tool to determine authenticity of various types of archaeological objects—in particular West Mexican
ceramic (Aronson & Kingery 1991) and stone (Garza-Valdes & Stross 1992) artifacts, as well as Egyptian limestone sculpture (Hochfield 1978).
Many aspects of the accretion’s genesis, rate of formation, as well as its physical and chemical characteristics remain unclear due to difficulties in its chemical and analytical characterization.
For example, micro-chemical spot tests, used to identify the presence of the manganese or iron in samples, have proved to be unsuccessful for specific identifications. Analysis of
numerous West Mexican ceramics in the collection of the Department of the Arts of Africa, Oceania and the Americas at the Metropolitan Museum of Art and Chihuahuan ceramics in
the collection of the Arizona State Museum, University of Arizona, has led to the establishment of at least 5 different morphological types easily identifiable with the aid of an optical
microscope. Specific relationships between accretion morphology and substrate characteristics (porous/non-porous, pigmented/unpigmented, painted/unpainted, burnished/unburnished,
slipped/unslipped) are made suggesting several conclusions regarding the mechanism of formation. Cross section analysis of accretions has confirmed author observations indicating
this surface phenomenon is not simply accreted or deposited. Chemical characterization of the various accretion forms has been undertaken using energy dispersive spectrometry (EDS)/
scanning electron microscopy (SEM), x-ray diffraction (XRD) and, x-ray fluorescence (XRF). The results of this research will enable conservators, archaeologists and curators to easily
identify a multiplicity of accretion morphologies in a variety of settings using simple analytical tools.
