Raman Spectroscopy in Archaeology and Art History. Volume 2

368 Pages·2019·24.92 MB·English

by  Peter Vandenabeele (Editor)

Raman Spectroscopy in Archaeology and Art History
Volume 2

Raman Spectroscopy in
Archaeology and Art History
Volume 2
Edited by
Peter Vandenabeele
Ghent University, Belgium
Email: [email protected]
and
Howell Edwards
University of Bradford, UK
Email: [email protected]
Print ISBN: 978-1-78801-138-9
PDF ISBN: 978-1-78801-347-5
EPUB ISBN: 978-1-78801-565-3
A catalogue record for this book is available from the British Library
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Foreword
Raman spectroscopy did not feature in my undergraduate degree in Archae-
ological Sciences in the 1980s. At the time, Howell Edwards was actively
extending research applications of Raman spectroscopy at my alma mater,
the University of Bradford, UK, but in the Department of Chemistry in an
adjoining building on the campus. Today, thanks to Howell, Peter Vanden-
abeele and many other researchers, Raman spectroscopy is included in the
teaching of a much wider range of degree subjects spanning the archaeo-
logical, heritage, environmental and forensic sciences. This is testimony to
the versatility of Raman spectroscopy as a diagnostic analytical tool. Further-
more, the research horizons of the technique have continued to expand and
this timely follow up to the 2005 volume is welcome.
In the late 1990s and early 2000s, Raman spectroscopy was acquired by sev-
eral of the major museum science and conservation laboratories. Following
the installation of a Raman microscope in the British Museum in May 1999,
the first dedicated conference on Raman Spectroscopy in Art and Archae-
ology was held in the Museum in November 2001. The technique has been
used at the British Museum since then to study minerals, including pigments
and gemstones, some organic dyestuffs, corrosion products and so on. The
technique is often used in conjunction with other techniques, notably X-ray
fluorescence and X-ray diffraction.
The increasing miniaturisation and portability of analytical kit, fuelled
by developments in lasers, detectors, filters and more, is exemplified by
the diverse situations where Raman is now being deployed. Raman and
micro-Raman spectroscopy features in the multi-technique MOLAB or
mobile laboratory platform providing access to portable technologies for
in situ non-destructive investigation of artworks. Various spectrometers
have been used to produce immediate results in the field to guide sampling
strategies for ongoing archaeological excavations. Looking ahead to 2020,

Raman Spectroscopy in Archaeology and Art History Volume 2
Edited by Peter Vandenabeele and Howell Edwards
© The Royal Society of Chemistry 2019
Published by the Royal Society of Chemistry, www.rsc.org
v
vi Foreword
the Mars microbeam Raman spectrometer, a component of the Scanning
Habitable Environments with Raman & Luminescence for Organics & Chem-
icals (SHERLOC), will be mounted on the NASA Mars 2020 Rover and will
search for organics and minerals that may be associated with signs of past
life on the red planet. Another miniaturised Raman laser spectrometer (RLS)
will feature for first-pass analytical screening on board the ESA/IKI Roscos-
mos ExoMars 2020 mission in the search for life signatures.
The study of our heritage relies on close co-operation between curators,
conservators and scientists. All techniques must be subject to continuous
critical evaluation so that the advantages, disadvantages and implications
are understood clearly. I am delighted to see this second volume extend-
ing the applicability of Raman spectroscopy to a wider range of topics and
themes in cultural heritage.
Carl Heron
Director of Scientific Research
The British Museum, London, UK
Preface
This book forms a sequel to the first volume which appeared under the edi-
torship of John Chalmers and Howell Edwards in 2005, comprising some
twenty-five contributed chapters from eminent authors and researchers over
a wide-ranging field of topics, which all had the common theme of the appli-
cations of Raman spectroscopy to the characterisation of materials of rel-
evance to art history and to archaeological artefacts. The idea for this first
volume was generated by a ground-breaking meeting on the same topic held
at the British Museum in London in November 2001, sponsored jointly by
the Royal Society of Chemistry (Molecular Spectroscopy Group, Analytical
Division) and the British Museum under the joint chairmanship of Dr Ian
Freestone of the British Museum Research Laboratories and Professor How-
ell Edwards of the Chemical and Forensic Sciences Department of the Uni-
versity of Bradford. It was apparent at this meeting that a synergy existed
between analytical Raman spectroscopists who were leading the application
of their technique towards the rather novel area of art materials and archae-
ological artefacts and the special sampling considerations and data inter-
pretation that these demanded and the conservation scientists, museum
curators and archaeologists who required novel information to facilitate the
restoration and preservation of the objects in their curacy.
It is certainly the case that most vibrational spectroscopic studies of art-
work and archaeological artefacts carried out up to the last quarter of the
20th century were exclusively the preserve of the infrared spectroscopist;
there are several reasons for this, but the most important are that earlier
Raman spectroscopic instrumentation used Toronto mercury arc excitation
(of up to 3 kW power output), operating mainly at 435.8 nm, and photo-
graphic plates, or later, photoelectric recording. This required rather large
quantities of pure samples that were stable to high-energy visible radiation
and the total absence of fluorescence emission, which could swamp the

Raman Spectroscopy in Archaeology and Art History Volume 2
Edited by Peter Vandenabeele and Howell Edwards
© The Royal Society of Chemistry 2019
Published by the Royal Society of Chemistry, www.rsc.org
vii
viii Preface
Figure 1 Overview of the number of research papers published on Raman spectros-
copy of cultural heritage. Based on ISI Web of Science.
much weaker Raman scattering intensity. In the late 1970s, however, the
classic marriage of a laser Raman spectrometer with an optical microscope
with sensitive photon detectors revolutionised the range of applications that
could be undertaken using the new laser Raman microscopy and almost
immediately resulted in the first brief description of artefact analysis using
this novel instrumentation. In a recent survey of the literature in the decade
1997–2007, which has addressed Raman spectroscopic applications to art
and archaeology by Vandenabeele et al. (2007), the growth of the technique
can be clearly seen expressed as a proportion of the total number of papers
published in art and archaeology and this is reflected in data presented in
the Web of Science where an almost exponential increase in Raman papers
published in art and archaeology should be noted (Figure 1).
Also, a greater awareness is now apparent across several disciplines at the
arts/science boundaries, and particularly in the field of scientific conserva-
tion and restoration, because publications using Raman spectroscopic tech-
niques, and also complementary data, for studying artworks have appeared
in journals which hitherto had not attracted research work of this kind, for
example, Studies in Conservation, Journal of Archaeological Science, Archae-
ometry, and Antiquity as well as in the more mainstream spectroscopic lit-
erature. The growth of work specifically in the area of Raman spectroscopy
applied to art and archaeology has stimulated the acquisition of novel spec-
troscopic instrumentation and trained specialists by museums and a new
focus directed at the communication of the results forthcoming from these
studies. In addition, the analytical information derived from optical, spec-
troscopic and diffraction experiments on artwork is being used increasingly
to provide evidence for the authentication of high-value artwork in museum
collections and in the private domain and also for the scientific provenanc-
ing of unknown artworks; the success of this approach is dependent upon
Preface ix
the acquisition of data derived from the materials comprising the art object
or artefact at both the elemental and molecular levels.
In the twelve years that have passed since the publication of the first
volume on Raman Spectroscopy in Archaeology and Art History in 2005, a
steady growth in output in this field has occurred: from the first conference
mentioned earlier in the British Museum in 2001, dedicated international
meetings on Raman Spectroscopy in Art and Archaeology (RAA) have been
held in Ghent (2003), Paris (2005), Modena (2007), Bilbao (2009), Parma
(2011), Ljubljana (2013), Wroclaw (2015) and Evora (2017). Other mainstream
spectroscopy and art analysis conferences now hold dedicated sessions on
Raman spectroscopy in art and archaeology, for example, the International
Conference on Raman Spectroscopy, GeoRaman, InArt, Technart and IRUG
(formerly the Infrared Users Group and now the Infrared and Raman Users
Group). Additionally, several topics which were presented as novel exam-
ples or as typical case studies in the 2005 publication have now themselves
become more widely applicable: a particularly apposite example of one of
these is the adoption of non-destructive, handheld or mobile Raman spec-
trometers for the interrogation of artworks and artefacts in situ and in the
field.
In this second volume, the original idea of offering full peer-reviewed chap-
ters supported by individual case studies that describe the application of
Raman spectroscopy to specific examples selected from the area or artworks
and archaeology has been maintained. This book will give the reader a mea-
sure of the important contribution that the Raman spectroscopic technique
is making currently to the provision of information about the analytical
molecular composition of material relevant to artworks and archaeological
artefacts. The major questions that archaeologists, conservators and art his-
torians have regarding the characterisation of their specimens can be sum-
marised as follows:
● There is an artefact that requires analysis; what is the composition of
the material present?
● How much of that material is present – are there any other materials
present that we should know about?
● Where did this material originate?
● What, if anything, has happened to it in the burial environment, if
appropriate? Is there evidence of environmental or biological degrada-
tion and, if so, is this still ongoing?
● Are there “unusual materials” present which warrant further study?
Is there any evidence that the specimen has undergone unrecorded
restoration?
● Is the specimen or artefact genuine or a fake?
● The specimen is subject to strict protocols of preservation and only
non-destructive analysis is acceptable – can this be assured?
Whereas most of these can be addressed by the adoption of analytical
Raman spectroscopy, the main purpose of any data acquisition must be
incorporated in a holistic forensic approach that necessarily involves the