The cover of this book shows an example of Australian Aboriginal rock art from the Kimberley region of Western Australia, and is reproduced here by courtesy of Graham Walsh of the Takarakka Rock Art Research Centre. The paintings were first reported by the explorer Joseph Bradshaw (1891). Because they are unusual and the details are unique there has been some speculation as to their origin. And because these paintings have no direct connection with the traditional owners of the land they have not been retouched as part of tribal ceremonies as is often the case. They are deteriorating as the rock substrate ages and organic binders and pigments oxidize and polymerize, which demands that some conservation measures be initiated for their preservation for future generations.
The rock art paintings illuminate the twin aims of this book: the use of archaeometry to determine the age, and perhaps some of the forensic details about the artefacts under examination; and the use of scientific techniques of analysis to determine the most appropriate strategy for their conservation.
In this book we have assembled twenty chapters covering a wide range of research in the fields of scientific conservation of art and archaeometry. The common thread is the use of radiation in these analyses. And the term "radiation" is used in its widest possible sense. The book encompasses the use of electromagnetic radiation in its microwave, infrared, visible, ultraviolet, x ray and g ray forms (E = hn =hc/l), and the use of particulate forms such as electrons, neutrons, and charged particles for which the Planck's Law relation (l = h/p) applies. In many cases there is an interplay between the two forms: for example, proton induced x ray emission (PIXE), secondary ion mass spectrometry (SIMS).
As far as was possible the chapters have been arranged in order of ascending particle energy. Thus it commences with the use of microwaves and finishes with the use of g rays.
The authors were chosen on the basis of their expertise as practitioners of their particular field of study. This means that, for example: the mature fields of study such as the IR and UV study of paintings have been written by very senior researchers, whereas for the emerging fields of synchrotron and neutron techniques the chapters have been written by talented researchers at the commencement of their careers.
A variety of systems for citing references are used throughout this book. This followed a deliberate decision by the editors. Because this book is intended for a readership which includes upper level undergraduates and early career researchers it was thought that exposure to a variety of referencing techniques would be useful from a didactic point of view.
In Chapter 1 Professor Lawrence Conyers of the School of Archaeology of the University of Denver, USA, discusses the use of ground-penetrating radar (GPR) for the non-invasive study of buried archaeological features. In the past excavation of sites has been the cause of considerable damage to the sites. Furthermore: because of restricted budgets the mapping of sites by conventional techniques is not feasible. He gives practical insights into the strengths and weaknesses of the GPR.
In Chapter 2 Dr Paola Letardi of the Istituto per la Corrosione Marina dei Metalli, of the CNR, Genova, Italy, introduces a new technique for the study of the integrity of protective wax coatings on the surface of bronze, and other materials. This technique was brought into use by the Australian group (Otieno-Alego,V, Heath, G.A. Hallam, D.L. and Creagh, D.C., (1998) Electrochemical Evaluation of the Anti-Corrosion Performance of Waxy Coatings for Outdoor Bronze Conservation. In proceedings of the ICOM Conference, METAL98. Draguignan, France. 27 to 29 May 1998. [Ed. W. Mourey.. James and James. (Science Publishers), London: ISBN 1-873936-82-6] pp309-515). They have used it extensively for characterizing the wax coatings on bronze statues and monuments in the custody of the Australian War Memorial. This is a low frequency (<1 MHz) AC technique in which the impedance of an electrochemical cell, one electrode of which is the waxed surface, is measured. The variation of impedance with applied frequency gives a measure of the integrity of the wax coating. Paola gives a detailed account of the testing processes for cells to be used in field tests on bronze statues.
The next two chapters relate to a mature, but interestingly rapidly evolving fields of infrared (IR) and ultraviolet (UV) examinations of paintings, books, manuscripts, et cetera. These techniques are necessarily linked to the appearance of the artefacts in visible light. It is the change in appearance in the artefacts under stimulus by infrared or ultraviolet radiation which gives valuable information on the works of art being examined.
The advent of CCD devices and vidicon tubes, the universal availability of great computing power in small packages, and modern image analysis software packages has greatly enhanced the usefulness of these macroscopic techniques of analysis. The broad-band spectral response of digital cameras coupled to the use of a variety of sources of illumination enables pixel-by-pixel studies of the detail of artworks. Emeritus Professor Franz Mairinger of the Institute for Colour Science and Colour Chemistry of the Academy of Fine Arts, Vienna, Austrai, gives us the benefit of his very considerable experience in the fields of the IR and the UV examination of paintings in his contributed chapters (Chapter 3 (IR) and Chapter 4 (UV)).
Chapter 3 outlines the mechanics of undertaking IR examinations of materials. It discusses the properties of IR and the interaction of IR with materials. It gives practical details of radiation sources lenses, detectors and filters. Tables of appropriate sources, filters and detectors are listed, as is the change of colour of many artists' materials under IR illumination.
The UV and fluorescence study of paintings and manuscripts is discussed in Chapter 4. As in the IR case adiscussion of the properties of UV radiation is followed by a detailed discussion of available UV sources, filters, and photographic materials. Their application in both reflected UV and the UV fluorescence studies is discussed, and the colour changes of pigments due to fluorescence is tabulated. Illustrations of the effects of the various possibilities of examination are given.
Recent advances in the analysis of scattered infrared, visible, and ultraviolet radiation spectroscopically have provided researchers with an extremely valuable tool for the analysis of all types of materials of interenst to museum curators and conservators, and archaeologists. The technique described by Dr Vincent Otieno-Alego of the Raman Microscope Unit, University of Canberra, Australia, the Raman technique, has been widely used by museums, forensic scientists and geologists, and is an integral part of the training of students, both undergraduate and graduate, in the Conservation of Cultural Heritage Materials. In Chapter 5 he outlines the principles of operation of a Raman microscope. As well, he gives a comparison of the strengths of Raman microscopy vis a vis other analytical techniques in the study of pigments in manuscripts and paintings, and in the examination of paint flakes form objects. The use of the Raman technique to map areas to establish paint and ink overlays is also discussed.
Professors Ladia Musilek (Czech technical University, Praha, Czech Republic) and M. Kubelik (Technical University of Vienna, Austrai) discuss the use of thermoluninescence dating (TD or TLD) in Chapter 6. They discuss both the physical principles underlying the technique and how the technique is used to establish the dates of manufacture of objects which have been fired, ceramics, pottery, bricks and the like. They give an excellent exposition of the assessment of errors (random, systematic and context) in the establishing of the age of fired objects. The reader is directed the Chapters 12, 19 and 20 which deal with the problems of archaeological dating.
The use of synchrotron radiation (sr) sources by materials scientists is still comparatively new. It is only in the last decade that sr sources have been dedicated to the study of materials have existed. Prior to that their use was the exclusive use of high energy physicists. There has been a rapid growth in their use by materials scientists, to the extent that more than thirty sr sources worldwide. Synchrotrons which generate energy in the x ray region (the region used in most structural analyses) typically have energies greater that 2 GeV. For example: the Photon Factory at the Japanese Institute for High Energy Research, Tsukuba, Japan, operates with a circulating current of electrons (400mA at 2.5 GeV) and produces useful maximum x ray energies for a bending magnet of about 20 keV; the Advanced Photon Source at Argonne, USA operates at 6 GeV and produces useful maximum x ray energies of 80 keV). Synchrotron radiation sources are classified by the size of the spot which emits the radiation: values of about 40 nm rad are typical of Second Generation machine; 20 or less are characteristic of a Third Generation machine.
Whatever the energy to which the charged particle is accelerated the principles underlying the production of x rays is the same. When a charged particle is accelerated (as it is when it is deflected by a magnetic field) it radiates energy in the form of electromagnetic radiation the maximum energy of which is determined by the energy of the particle and the applied magnetic field. The higher the particle energy and the stronger the magnetic field strength, the higher the maximum photon energy, or put another way, the shorter the critical wavelength (lc =18.64/(BE2); where lc is in Angstrom, B in Tesla, E in GeV). See for example: U. Arndt (1992) The generation of x rays. In International Tables for Crystallography Volume C (Ed. A.J.C. Wilson: Kluwer, Amsterdam) Section 4.2, 172-175.
The principal properties of synchrotron radiation are as follows:
For the experiment described in Chapter 7 "white" radiation was used and the photon
energies were separated using energy dispersive analysis techniques. In Chapters 14 and 16 monochromatic radiation has been used. The production of monochromatic radiation and techniques for focussing the already highly collimated, high intensity beams has been described by Creagh (D.C. Creagh (1999). Monochromators and Filters. In International Tables for Crystallography Volume C Second Edition (Ed. E. Prince: Kluwer, Amsterdam) Section 4.2.5).
In Chapter 7 Drs. Sally Colston, Andrew Jupe and Paul Barnes of the Industrial Materials group, Crystallography Department, Birkbeck College, London, UK, introduce the new techniques of synchrotron radiation energy dispersive diffraction (SR-EDD) and synchrotron radiation energy dispersive diffraction imaging (SR-EDDI).. They give an outline of the theory underlying the techniques and the use of the technique for the study of a neolithic bronze tool and building materials. The interior of objects can be studied as a function of composition using tomagraphic techniques. Attention is given to the important question of data quality. Note that a variant of this technique (using conventional, rather than sr sources) is in use at major airports for the examination of passenger baggage, looking especially for explosive materials.
Another approach to the study of solid objects using x ray techniques was adopted by Dr. Mic Farquharson of the Department of Radiography, City University, London, England, and Dr. M. Brickley, Department of Ancient History and Archaeology, The University of Birmingham, England. They are interested in establishing a protocol for the proper estimation of bone mineral density (BMD) in bones, especially those of archaeological interest. In Chapter 8 they outline the principles of radiography, single (SPA) and double energy x ray analysis (DEXA), and energy dispersive x ray diffraction (EDXRD). One of their projects of topical relevance is a study of osteoporosis, then and now. Comparisons are made between populations in East London in the 18th century and those prevailing now. They studied the BMD of the fourth lumbar vertebra of the human skeleton. Details of their results are given.
Chapter 9 is the first of the chapters which use particulate radiation for the study of museum and archaeological objects. In this chapter Dr. Mieke Adriaens of the Department of Chemistry, University of Antwerp, Belguim, discusses the principles of Secondary Ion Mass Spectrometry. In this technique a finely collimated beam of ions is used to probe the surface of the sample. The secondary ions sputtered from the surface are characteristic of the composition of the surface layer. These are analyzed using a mass spectrometer. Hence the surface composition can be determined. As the ion beam eats into the surface a depth profile of the composition of the material can be generated. Numerous applications to the conservation of materials, dating and determining the provenance of materials are given. The reader should refer also to Chapter 18 on Proton Induced X ray Emission (PIXE) and Chapter 19 on Accelerator Mass Spectrometry (AMS).
The use of a variety of scanning electron microscope techniques for the study of paintings is given in Chapter 10 by Dr. Aviva Burnstock, Department of Conservation and Technology, Courtauld Institute of Art, London, England, and Dr. Chris Jones, Electron Microscope Unit, Department of Mineralogy, The Natural History Museum, London, England. The chapter focusses on the imaging of the materials used in easel paintings, rather than using x ray techniques for the chemical analysis to study compositions. Examples of experimental studies of cleaning, paint surface defects, and bio-degradation of painting materials are given. A compilation of images of selected artists' materials is given to illustrate a number of SEM techniques. Further relevant discussion is contained in Chapter 11 (Transmission Electron Microscopy) and Chapter 5 Raman Microscopy.
The use of transmission electron microscope techniques for the identification of pigments taken from easel paintings is discussed in Chapter 11 by Shaun Bulcock of the Electron Microscope Unit, University of Sydney. He outlines the principles underlying the formation of transmission electron microscope patterns, in particular the selected area diffraction (SAD) and convergent beam electron diffraction (CBED) patterns. He then proceeds to give examples of studies made on small paint fragments from two artworks in which CBED was used in conjunction with energy dispersive x ray analysis (EDAX or EDS) to determine the mineral composition of the fragments. In particular comparisons should be made with the results of Raman microscopy ( Chapter 5).
The second of the archaeological dating techniques to be reported in this book is radiocarbon dating (14C dating). In Chapter 12 Drs. Tom Higham and Fiona Petchey, Radiocarbon Dating Laboratory, University of Waikato, Hamilton, New Zealand, discuss the physical principles of radiocarbon dating and its use in archaeometry. They give a detailed outline of error assessment and they stress the requirements for quality assurance. They discuss matters of sample selection, sample provenance, and sample contamination in the context of archaeological research in Australia and New Zealand. Chapters 19 and 20 also discuss the strengths and weaknesses, successes and failures of radiocarbon dating.
In Chapter 13 Dr Marco Ferretti of the CNR-Istituto per le Tecnologie Appiacate ai Beni Culturali discusses the use of X ray Fluorescence Analysis (XRF) for the study of works of cultural heritage significance. He reviews the literature on this subject and outlines the criteria which must be fulfilled if accurate analyses are to be made using this technique. Results for metals, pottery, glass and paintings are given.
Professor Pauline Martinetto, Dr. G. Tsoucaris, Dr. P. Walter (Laboratoire de recherche des musees de France, Paris, France), Dr. M. Anne (Laboratoire de Cristallographie-CNRS, Grenoble, France), and Eric Dooryhee (European Synchrotron Radiation Facility, Grenoble, France) have used the technique of synchrotron radiation to study the composition of Egyptian cosmetics of the pre-dynasty, New-, and Old-Kingdoms. In Chapter 14 they describe the use of monochromatic synchrotron radiation to study the structure of the components of the cosmetics, using a focussed beam to illuminate particles as small as 10 mm. The technique of Rietveld analysis has been used to determine the composition of mixed phase samples.
Professor Peter Yu of the Department of Physics and Materials Science, City University of Hong Kong, P.R. China, is an expert in the attribution of provenance of Chinese blue and white porcelain. In Chapter 15 he outlines some of the problems and challenges in the study of these ceramics. He discusses: the feasibility of using ratios between elemental concentrations for the attribution and the feasibility of using for our criteria some elements characteristic of the colorant (such as Mn and Co) which in theory lies too deep beneath the glaze to be measured; the soundness of calibration sources; the need to use multivariate analysis instead of contents for individual chemical elements; the properties of antique blue and white porcelains other than those of the Qing dynasty, in particular those of the Ming dynasty; the properties of antique blue and white porcelains of the Qing dynasty (separated from the porcelains of the Republic period) and those in different periods of the Qing dynasty, and comparison between Qing and Ming porcelains; properties of antique blue and white porcelains from different main sites of production, including those from the most studied site of Jingdezhen.
Dr. Winfreid Kockelmann (ISIS Facility, Rutherford Appleton Laboratory, Chilton, England), Dr. Manolis Pantos (SRS Facility, Daresbury Laboratory, Warrington, England), and Professor A. Kirfel (Mineralogisch-Petrologisch Institut, Universitat Bonn, Germany) have used both time-of-flight neutron and synchrotron X-ray diffraction were used for fingerprint determinations and quantitative mineral phase analyses of archaeological objects. In Chapter 16 they discuss the advantages and drawbacks fo both techniques in archaeological research. Neutron diffraction allows non-destructive analysis of complete and unprepared objects. Synchrotron X-ray diffraction can be used for fast and high-resolution data collection on small amounts of powder samples, surfaces or thin sections. Their paper concentrates on the introduction of the white-beam neutron diffraction technique to the study of pottery from ancient Greek, Russian and German sources.
In Chapter 17 Dr Maria Guerra of the CNRS-Centre Enerst-Babelon, Orleans, France, gives a general description of a wide range of radiation techniques ( activation techniques using neutrons (NAA) and protons (PAA), proton induced x ray emission (PIXE) and x ray fluorescence spectroscopy (XRF) can be used for determining the provenance of metals, and developing an understanding of the manufacture technology of metallic objects in ancient times. The main properties and differences for the most used techniques are given. Some, used to complement radiation techniques and used in the later examples, are also considered.
She gives several examples, most of them on coinage, for the most important non-ferrous metals and alloys used in the past. These cover a large but far from complete number of fields of research. She demonstrates that provenance may sometimes be determined by using trace elements patterns. However, for more accurate results a good knowledge of trace elements present as well the geological context is required. To understand the fabrication of an object we need in general to couple both analytical and metallurgical data.
A large number of examples illustrate the questions posed for metalwork. For each main metal, after some geological, smelting and purification considerations, application of the radiation techniques to the manufacture technology and the provenance of the ores were considered to answer a number of particular historical questions.
The Mossbauer effect has been used with some success to solve problems associated with archaeology and conservation. Mössbauer spectroscopy makes use of low energy g-rays emitted by nuclei for studying the properties of solids. In Mössbauer studies of works of art and archaeological ceramics, the 14.4 keV g-rays of 57Fe are used in most cases, although other Mössbauer isotopes, like 119Sn and 121Sb, can also be used, for instance, for studies of bronzes or glazes containing tin or antimony, while 197Au has recently been used for studying Celtic gold coins. In Chapter 18 by Professors Ursel and Fritz Wagner, Dr. W. Hausler and Dr. I Shimada of the Physics Department, Technical University of Munich, Garching, Germany, only 57Fe Mössbauer spectroscopy and its application to studies of ceramics is discussed. The ceramics discussed in this context are mainly pottery, but also building materials such as fired bricks and tiles as well as parts of kilns and furnaces or even soil or mud-plaster heated in fires.
In Chapter 19 a different approach to radiocarbon dating from that of Chapter 12 is introduced by Drs. Claudio Tuniz, Ugo Zoppi and Marco Barbetti of the Australian Nuclear Science and Technology Organization, Sydney, Australia. As mentioned in Chapter 12 radiocarbon (14C) dating provides an absolute time scale for human history over the last 50,000 years. Accelerator Mass Spectrometry (AMS), with its capacity to analyse 14C in sub-milligram carbon samples, has expanded enormously the applicability of this dating method. Specific molecular compounds extracted from ancient bones, single seeds and other microscopic carbon-bearing substances of archaeological significance can now be dated, increasing the sensibility and reliability of the chronological determination. Thanks to the very limited invasiveness of AMS, rare artefacts can be sampled for dating without undue damage. The state of the art in AMS dating of objects significant for archaeology, history and art is reviewed with examples from some recent applications such as Australian rock art, the Shroud of Turin, the "iceman" mummy, and Charlemange's crown.
Chapter 20 introduces techniques for dating of materials which complements and extends the capabilities of techniques described in Chapters 6, 12, and 19. In it Professor Rainer Grun of the Research School of Earth Sciences, Australian National University, Canberra, Australia describes how dating can be extended beyond the limits of radiocarbon dating. The U-series and trapped charge dating methods he describes can be applied for the establishment of chronologies well beyond the radiocarbon dating barrier. His chapter gives a short introduction into these methods and illustrates their potential with the dating of the Lake Mungo 3 skeleton. The determination of the age of this skeleton is of importance for the assessment of theories concerned with the manner in which Australia was inhabited.
One invited chapter, mailed but not received at the time this book needed to go to press, was that by Dr L Ciancabilla and Dr G. Maino of Facolta di Conservazione dei Beni Culurali, Universita di Bologna, Ravenna, Italy on The Study of Art and Archaeological Artefacts using Ion Beam Analysis, PIXE and Reflectography. The authors have a formidable reputation for the quality of their research on a wide range of objects of cultural heritage significance. The possibility of its being published in the journal Applied Radiation and Isotopes will not be overlooked.
D.C. Creagh and D.A. Bradley