SCIENTIFIC ANALYSIS OF ARCHAEOLOGICAL OBJECTS IN MUSEUMS

SA19 SCIENTIFIC ANALYSIS OF ARCHAEOLOGICAL OBJECTS IN MUSEUMS: MODERN TECHNOLOGIES AND LIMITATIONS OF THE COLLECTIONS

Prof. Robert Tykot, University of South Florida. Dr. Andrea Vianello, Oxford University

Museum and storage collections have been increasingly targeted by new research thanks to the availability of portable analytical equipment (e.g. portable XRF, XRD, Raman, NIR, FORS). At the same time, conducting any kind of destructive analysis or having to transport the materials out of the museum is more regulated and often limited. When compared with traditional laboratory-based analytical methods, there are technical and human issues that raise questions about the results produced by portable instruments. Do they produce the same quality results? Can they still answer the research questions being addressed? Depending on the material being tested, what are the limitations of conducting non-destructive analyses? If only small powder samples rather than solid pieces are allowed, is that sufficient? What kind of training is necessary? At the same time, many of the objects on display in museums are from older excavations or surface collections, or were acquired by purchase or donation, and thus lack detailed contextual information. Frequently, they are not representative of all the artifacts that were excavated or collected. Certain materials have been specially cleaned or treated with preservatives, while others are weathered or in some stage of decay. How can this be dealt with? We welcome presentations focusing on real-world cases in which any of such issues have been faced. Any materials including lithics, ceramics, metals, glass, organics, and paintings can be discussed. We also invite presentations on the ethical and practical conditions involved in archaeological museum studies, including those related to identification of forgeries. Our aim is to produce an updated review of methods, pitfalls and solutions for conducting scientific research outside the laboratory.

 

SA19 Scientific Analysis of Archaeological Objects in Museums: Modern Technologies and Limitations of the Collections

ALEXANDER STONE BUILDING - ROOM 204

THURSDAY 3RD SEPTEMBER 2015

Organiser(s): Prof. Robert Tykot, Dr. Andrea Vianello

1330 - 1340

Introduction

1340 - 1400

The museum collection as archaeological assemblage, Vianello, A (independent researcher)

1400 - 1420

A big ask? Sampling composite ceramic assemblages for scientific analysis, Sibbesson, E (Canterbury Christ Church University)

1420 - 1440

Advantages and Limitations of Using Non-Destructive Portable X-Ray Fluorescence Spectrometers (pXRF) in Museums: Studies of Metals, Ceramics, Lithics, and Paintings, Tykot, R (University of South Florida)

1440 - 1500

All that glitters is not gold: about some of the limitations and strengths of non-destructive analyses on archaeological pottery, Iñañez, J (University of the Basque Country (UPV/EHU) - IKERBASQUE)

1500 - 1520

Surface pXRF analyses of the Chalcis Treasure from the Ashmolean and British Museums, Orfanou, V (Institute of Archaeology, UCL)

1520 - 1530

Discussion

Coffee break

1600 - 1620

Informative potential of the collection objects obtained by reverse engineering, Escobar Gutiérrez, J (Universidad de los Andes); Bustamante, N; Rueda, N; Cano, S; Barbosa, J

1620 - 1640

Museum artefact biographies: aspects and issues for microwear and provenance analyses in circum-Caribbean collections, Breukel, T (Faculty of Archaeology, Leiden University); Falci, C; Knaf, A; Koornneef, J; Van Gijn, A; Davies, G

1640 - 1700

Sorting Out the Dead: Using pXRF As An Aid To Individuate Commingled Human Remains, Richards, J (UW-Milwaukee); Richards, P

1700 - 1800

Discussion - Discussant: Keri Brown

 

 

ABSTRACTS

SA19 THE MUSEUM COLLECTION AS ARCHAEOLOGICAL ASSEMBLAGE

Andrea Vianello

INDEPENDENT RESEARCHER

Scientists usually sample materials and artefacts for their researches. But this is done with the understanding that the sample is representative of the total and under controlled conditions as much as possible. Having a reliable context is also considered as critical. As a result, scientists prefer to analyse materials from current or recent excavations, in the belief that this practice will avoid most problems. In fact, archaeology can only retrieve a small to tiny percentage of the original artefacts, and time selects and distorts both quantities and types of preserved materials to a degree that none of the other fields of application of scientific techniques has to deal with regularly. Current excavations are often partial, and besides, even completed excavations are rarely systematic. In addition, archaeologists like to cherry-pick materials that they find unusual or spark their interest, introducing an artificial bias.

It is obvious that scientific research in archaeology can really achieve valid data for interpretations only as comparable data sets grow to a larger size. Individual publications of small data sets is essential, but the recognition of patterns or other useful aspects needs to be tested and validated from multiple similar assemblages, or any information will be very limited and applicable to the few artefacts and materials analysed. Existing museum collections can provide large amounts of materials from multiple sites with little bias added if the materials have been preserved without particular selection, and allow reaching a good size of tested materials for nearly any class of materials.

 

 

SA19 A BIG ASK? SAMPLING COMPOSITE CERAMIC ASSEMBLAGES FOR SCIENTIFIC ANALYSIS

Emilie Sibbesson

CANTERBURY CHRIST CHURCH UNIVERSITY

Organic residue analysis (ORA) of ceramics can be undertaken on samples selected directly in the field or from collections in museum stores. In this paper I discuss the complexities involved in re-visiting ceramic assemblages held in museums. Until recently, archived ceramic assemblages were the jurisdiction of specialists trained in the traditional methods of ‘hand-held’ analysis. Today, assemblages are also interrogated using an expanding array of scientific techniques, and sample selection is a crucial stage in the scientific process. However, I suggest that poor understanding of traditional approaches to ceramic study and to the ways in which ceramic assemblages are created in museums can have repercussions for later stages of scientific research, primarily interpretation and communication of results. Using examples from recent ORA-studies of British prehistoric pottery, I suggest that ‘composite’ assemblages from large sites that were excavated multiple times by different teams present the biggest challenges. With this in mind, I discuss the ways in which these predicaments can be redressed.

 

SA19 ADVANTAGES AND LIMITATIONS OF USING NON-DESTRUCTIVE PORTABLE X-RAY FLUORESCENCE

SPECTROMETERS (PXRF) IN MUSEUMS: STUDIES OF METALS, CERAMICS, LITHICS, AND PAINTINGS

Robert Tykot

UNIVERSITY OF SOUTH FLORIDA

Many methods of elemental analysis have been successfully used on archaeological materials to address their overall composition or specific elements to identify the source of their geological components. But in many cases, only non-destructive analysis is allowed, and perhaps only allowed within the museum. In recent years, non-destructive portable XRF instruments have become widely used, on virtually any size artifact, and producing data for one hundred or more objects per day.

Presented here are the advantages and disadvantages of using a pXRF in such circumstances, based on my experience for eight years on thousands of metal, ceramic, lithic and other artifacts in museums and storage facilities around the world.

Issues have been raised about the sensitivity, precision and accuracy of these devices, and how to compare pXRF data from different brand instruments as well as with other analytical methods. This may be resolved by using the same analytical settings, analysis of standard reference materials, and the calibration software utilized. Limitations of non-destructive pXRF include performing surface analysis on potentially heterogeneous materials like ceramics, and its detection limits not as low as regular XRF instruments.

Examples of the research presented here, emphasizing the advantages and limitations for specific materials and archaeological questions, include the composition of copper and other metal alloys; sources and trade of lithics (obsidian, chert, marble) and ceramics (pottery, figurines); and the use of paint pigments. These analyses have been conducted within museums in Croatia, Ethiopia, Greece, Italy, Kuwait, Malta, Norway, Peru, and the United States.

 

SA19 ALL THAT GLITTERS IS NOT GOLD: ABOUT SOME OF THE LIMITATIONS AND STRENGTHS OF NONDESTRUCTIVE

ANALYSES ON ARCHAEOLOGICAL POTTERY

Javier Iñañez

UNIVERSITY OF THE BASQUE COUNTRY (UPV/EHU) - IKERBASQUE

Non-destructive analytical techniques have emerged during the past years as an indispensible tool for archaeologists and museum professionals. Nowadays, these non-destructive and usually portable techniques are widely applied to numerous and heterogeneous kind of artifacts in museum collections, from natural (e.g. stony materials) to synthetic materials (e.g. ceramics or metals). Although the socialization and spread of such technologies may be interpreted as an important step forward for the Archaeological Community, several problems may be pointed out. Thus, and from the experienced gained in the past years, it is important to clearly highlight that such techniques should not be considered by no means as some kind of a “black box”. On the contrary, the limitations and strengths of any instrument and technique depending on the nature of the material to be study should be known in advance in order to generate reliable data. Experiences from the field of pottery analyses will be discussed, including provenance and technological studies.

 

SA19 SURFACE PXRF ANALYSES OF THE CHALCIS TREASURE FROM THE ASHMOLEAN AND BRITISH MUSEUMS

Vana Orfanou

INSTITUTE OF ARCHAEOLOGY, UCL

Vana Orfanou1 and Nikos Kontogiannis2

1 INSTITUTE OF ARCHAEOLOGY, UNIVERSITY COLLEGE LONDON, 2WASHINGTON & HELLENIC MINISTRY OF CULTURE

Quantitative surface analysis with portable XRF equipment has taken place on the Chalcis Treasure which is currently kept jointly at the Ashmolean and British Museums. The hoard, recovered at Chalcis in Euboea, Greece, is dated to the 15th century AD, with the Ottoman invasion of Chalcis in 1470 providing a terminus ante quem, and consists of precious metals alloys. The assemblage comprises a large selection of jewellery articles, dress ornaments and cloak accessories including various types of rings, earrings, buttons, belt buckles and mounts. Chemical characterisation of some one hundred artefacts aimed to examine the technological attributes of the different artefact types in order to shed light on the circumstances of their production, use and deposition. The paper discusses the limitations relating to the nature of the artefacts themselves, the instrument used and to the circumstances of the assemblage’s safekeeping in museum collections. These, for example, include the metal alloys heterogeneity and potential surface treatments of the objects as many bear traces of mercury gilding which along with the surface analyses conducted need to be addressed in order to avoid a misleading interpretation of the assemblage.

 

SA19 INFORMATIVE POTENTIAL OF THE COLLECTION OBJECTS OBTAINED BY REVERSE ENGINEERING

Jairo Arturo Escobar Gutiérrez, Nohora Bustamante, Natalia Rueda, Santiago Cano, Juan David Barbosa

UNIVERSIDAD DE LOS ANDES

Metallurgy was an important activity developed by social groups -that inhabited the actual territory of Colombia- in pre-Hispanic times. This activity must have been involved with their customs, ideology and practices, as it was expressed in their material culture. Proof of it is the collection of nearly 40.000 objects stored and displayed within the Gold Museum in Bogotá and more than thirty other museums around the world. Most of these "objects" lack of archaeological context, as they are the product of “guaquería”, the act of robbing tombs or graves. This difficulty has limited archaeological research, but also has stimulated investigation on artefacts themselves, as they are evidence of their goldsmiths and their metallurgical technologies.

This work aims to demonstrate the informative potential of the "objects" by using the reverse engineering methodology and tools such as theoretical models of industrial corrosion; computational simulation, utilizing FLOW3D Cast software; and analytical measurements as XRF, SEM-EDS, EBSD and XRD. Both methodology and tools allowed to propose manufacture hypotheses and their corresponding validation through experimental replicas.

One of our projects using an industrial corrosion model, allowed to model and replicate the depletion gilding process of Tairona Goldsmiths. Another project consisted on digitally rebuilding a lost Muisca raft and its casting process by using historical sources only. One third project using a 300 micrometers thick fragment analysis, belonging to a Nariño goldwork -provided by the Gold Museum- revealed a cycling including cold work (plastic deformation) upon only one of its faces and annealing.

 

SA19 MUSEUM ARTEFACT BIOGRAPHIES: ASPECTS AND ISSUES FOR MICROWEAR AND PROVENANCE ANALYSES

IN CIRCUM-CARIBBEAN COLLECTIONS

Tom Breukel1, Catarina Falci1, A. C. S. Knaf2, J. M. Koornneef2, A. L. Van Gijn2, G. R. Davies2, C. L. Hofman2

1FACULTY OF ARCHAEOLOGY, LEIDEN UNIVERSITY, 2

In the circum-Caribbean, the core of museum collections is composed of objects unsystematically collected in the past 500 years. Materials recovered from controlled excavations are often also under the custody of national museums, emphasising the need for collection research. Nonetheless, artefacts bearing patrimonial value tend to accumulate complex post-excavation itineraries in which archaeological information is superimposed and erased. This underlines the need to focus on entire artefact biographies, addressing pre-depositional (raw material provenance, production technologies, use) and post-excavational trajectories (curatorial treatments, surface degradation).

In this paper we consider the challenges faced when conducting microwear and provenance studies on museum artefacts. Microwear analysis is conducted to assess technological traditions and modes of use. Traces are observed on shell, lithic, and coral artefacts using a portable field microscope and incident light microscopes in the laboratory (10-500x). Comparison of lithic artefacts and possible source rocks is applied to potentially permit full characterisation of past mobility and exchange networks. Newly developed multi-element and -isotopic analyses require only microgram amounts of material. A portable, macroscopically non-destructive, laser sampling device allows us to sample museum collections prior to lab analysis. The microscale sampling avoids disturbance of worked surfaces permitting the combined geochemical-microwear approach.

We reflect upon concerns and strategies required to produce reliable data from artefacts, with regards to access, context, and surface alteration. Our analytical results allow the separation of features pertaining to pre-depositional and post-excavational events, ultimately generating more complex scenarios for circum-Caribbean archaeology.

 

SA19 SORTING OUT THE DEAD: USING PXRF AS AN AID TO INDIVIDUATE COMMINGLED HUMAN REMAINS

John D. Richards, Patricia B. Richards

UW-MILWAUKEE

The analytical utility of museum collections of human remains accessioned during the late nineteenth century or early part of the twentieth century is often compromised by a loss of association between individual skeletal elements and specific burials or burial contexts. In some cases this is due to recovery procedures that failed to include methods for recording detailed provenience information. In other cases, the lack of provenience data is attributable to accessioning practices, post-accession analyses that mixed remains, or curation programs that deemphasized provenience in favor of efficient storage procedures. Nonetheless, the research potential of many of these kinds of collections is quite high as they often represent the only extant examples from important archaeological sites. However, the value of such collections could be leveraged if a non-invasive, relatively time and cost efficient method of re-associating commingled skeletal elements could be found. Recently, forensic researchers have reported success in using handheld portable x-ray fluorescent analyzers (pXRF) to identify individuals in archaeological assemblages and collections of anatomical specimens. Use of this approach in museums is often constrained by conservation requirements that mandate minimal handling and restrict cleaning of bone surfaces and thus reduce the efficacy of the pXRF technique. This paper reports the results of a pXRF study of museum collections of archaeologically recovered human remains and suggests best practices for using pXRF as an aid in sorting commingled human remains in curated museum collections.