The analysis of medieval European manuscripts
Mark Clarke
Abstract
The benefits of analysing the materials of manuscripts, particularly pigments, are outlined. The
difficulty of analysing manuscripts, compared to that for other artefacts, is explained. The
development of the analysis of manuscripts, the techniques used and the results reported, are
reviewed. Suitable techniques are identified, and their strengths and weaknesses are assessed.
Tables are given, which provide keys to the published analyses, indexing them by date and by the
techniques used. The results of these published analyses are collated in a referenced table, showing
those pigments that have been positively identified by reliable techniques, by century, for medieval
European manuscripts.
Table 1. Abbreviations used in the text
3DF
EDX
FTIR
HPLC
IR
IRFC
MS
PIXE
TLC
UV-Vis
XRD
XRF
3-Dimensional Fluorescence spectrometry
Energy Dispersive X-Ray analysis
Fourier-transform Infra-Red spectrometry
High Performance Liquid Chromatography
Infra-Red spectrometry
Infra-Red False Colour photography
Mass Spectrometry
Particle Induced X-Ray Emission
Thin Layer Chromatography
Ultraviolet-Visible spectrometry
X-Ray Diffraction
X-Ray Fluorescence
Introduction
This paper reviews a selection of published analyses of paint on manuscripts. It covers both the
materials identified and the methods used to make these identifications. Publications that describe
techniques particularly clearly, or which describe unusual techniques are given preference. The
techniques described here may of course be used on any work of art on paper or parchment, but this
review concentrates on the results of analyses of medieval European manuscripts. Results from
further publications are included in summary tables.
Considering the large amount written about medieval manuscript decoration there have been
surprisingly few analyses published. The study of the materials used for making manuscripts is,
compared to the study of paintings on other supports, in its infancy. The main obstacle has been the
aspiration not to take samples for analysis. The consequence of this has been that for a long time the
only analysis possible was visual examination.
Issues in manuscript analysis
Sampling versus 'non-destructive' analysis
'Non-destructive' to a chemist usually means that the sample is not consumed or altered during
analysis, and that it may be recovered afterwards in pristine condition. 'Non-destructive' to a curator
or conservator usually means that the artefact is not altered. Removal from the artefact of a sample
is therefore viewed as 'destructive', regardless of whether the sample survives the analysis.
For many painted artefacts sampling is commonly acceptable. It is almost always possible to take
samples for microscopic examination (typically cross-sections to reveal layer structures), or for
micro-chemical or instrumental analysis. A typical paint sample mechanically removed using a
scalpel is tiny: a microgram or so. The gap it leaves in the painted surface is almost invisible to the
naked eye, being a fraction of a millimetre wide. Because the paint layer is relatively thick, there is
quite a lot of material present from which information can be extracted. However, the paint and ink
layers on decorated manuscripts or other works of art on paper are typically very thin compared to
those on other coloured items such as easel paintings, murals or polychrome sculpture. The painted
decoration also usually covers only a relatively small area - perhaps a few square centimetres or
even millimetres. Removing a sample sufficiently large to be analysed may result in an area of loss,
which, while it would have been far from obvious on a large object, will often be comparatively
conspicuous, usually to an unacceptable degree. In consequence, it is generally considered to be
unacceptable to take samples from manuscripts, and a great many curators will not permit it. This
preference may have developed in part from increasing interest and appreciation of the value of
manuscripts, in part from increased curatorial awareness of conservation issues, particularly for
works on paper, and in part from a growing awareness among curators, conservators and even art
historians of the availability of analytical equipment of greatly improved sensitivity.
This is not to say that no analyses of manuscripts have been carried out using sampling. Where
analysts used samples, this is indicated below. Sampling may be justified on several grounds, well
summarized by Orna and Matthews in 1981 [1]. Despite being aware of in situ techniques, they
performed sampling with a scalpel and a microscope. Where samples were taken '...the lacunae
were hardly discernible under the microscope, much less by the naked eye' [1, p. 62]. They further
justified their standpoint:
'Given the availability of samples from a manuscript, there is no substitute for the 'good oldfashioned' methods of analysis of microscopic particles. Given that [certain methods of in situ
analysis] are non-destructive, it is the position [of Orna and Matthews] that taking pigment samples
from a manuscript can be equally non- destructive. First, sample-taking does not require removal
of the manuscript from its permanent location. Secondly, the sampling, if well-planned, is a onetime operation which need never be repeated. Thirdly, sample-taking involves much less handling
of the manuscript than [in situ] methods' [1, p. 60].
Their fourth point applies to certain techniques such as auto-radiography, for which '...only the
samples, and not the entire manuscript, are subjected to high-energy irradiation...' [1, p. 61].
If carried out with sufficient care even samples large enough for polarizing light microscopy may be
taken without visible damage. Increasingly sensitive methods of analysis need ever-smaller
samples, and if sampling is done carefully these are undetectable to the naked eye. More recently
micro-samples have been obtained by gently rubbing the surface of a miniature with a small cotton
swab, which results in no visible alteration to the decoration. [2-5]. An alternative approach is to
confine sampling to areas already damaged [6, 7].
Fingerprinting versus analysis
From a person's fingerprint you cannot deduce that person's appearance, but you could compare an
unknown fingerprint with one of a specific individual and so know if it was left by that individual.
Many analytical techniques are only to a limited extent truly analytic, i.e. only to a limited extent
can they indicate what is there if you do not already have some idea. What they do allow is
comparison of unknown samples with known ones. In other words, having once prepared samples
of known composition (for example, by following medieval recipes), analyses and spectra can be
prepared from them. Then, when you have an unknown sample taken from an artefact, you may
compare the results and thus determine what was present. This approach to analysis may be
described as 'fingerprinting'. Fingerprinting techniques require a short-list of candidate materials to
be drawn up, using educated guesses based on documentary sources, previous analyses, etc.
Fingerprinting techniques include visual examination, and IR, Raman and UV-Vis spectrometry.
While it is possible to assign certain spectral features to certain molecular structures, and so deduce
part of the structure of an unknown sample, in practice, for pigment analysis, spectra are used as
fingerprints. Non-fingerprinting analytical techniques include the elemental techniques, such as
XRF, PIXE and EDX, where information as to exactly what component elements are present is
obtained.
Mixtures
When samples are taken, it is often possible to separate out components of a paint, i.e. the binding
medium or media, mixtures of pigments or dyes, and any other additives. These can then be
identified individually. Using non-sampling techniques, this is not possible, as the components of
the mixtures will interfere with each other. Spectral peaks due to binding media can swamp lowintensity peaks from pigments in such techniques as Raman, IR or fluorescence techniques. IR and
UV-Vis spectra frequently become un-interpretable when there are mixtures, as the multiple peaks
combine to form broad meaningless plateaux. Even elemental analysis is complicated by several
pigments having elements in common; for example a red paint showing peaks for lead may contain
red lead, or red lead and white lead, but it may alternatively contain white lead plus some organic
red. Raman microscopy is proving a powerful tool in the analysis of mixtures, as the optics can
allow individual pigment grains to be selected for analysis, although for this to work, the parchment
must not be moving too much (e.g. through vibration, inadequate support, or fluctuating relative
humidity), and the specimen must be able to lie on the microscope stage.
Comparisons of analytical results with those from reconstructed samples
It has become common to proceed by reviewing contemporary written technical sources, or 'recipe
books', followed by preparing reconstructed reference samples based on these sources, and then by
comparing analyses of these standards with analyses of artefacts. Examples of literature comparing
sources with the analyses of manuscripts sharing a date and place of manufacture include 8, 9 and
10. Of course, for such comparative techniques to succeed fully, firstly there must be samples made
up of all possible pigment and medium combinations, secondly the pigments on manuscripts to be
examined must be a subset of these samples, thirdly modern raw materials must produce similar
results to medieval ones, and fourthly ageing over 1000 years must have no significant effect on
analysable properties. As there is no guarantee that all or any of these criteria will hold, any
practical work can only hope to approximate to these ideal conditions.
Medieval written technical sources
These are too many, varied, and problematic to discuss in detail here. Clarke, 2001, catalogues and
describes over 400 European manuscripts from before c. AD 1500, which contain such texts [11].
Convenient introductions to the subject are Clarke, for an overview of the period, a guide for further
reading and a catalogue of manuscripts, their editions and translations [11], Roosen-Runge, for the
earliest treatises [9], Hawthorne and Smith, for Theophilus [12], Merrifield, for a wide range of
material from the twelfth to eighteenth centuries [13], and Thompson, for the fourteenth-century
treatise of Cennino Cennini [14].
General works on pigment history
Still often cited are Thompson 1936 [15], Gettens and Stout 1942 [16], Forbes 1965 [17] and Singer
et al. 1954-84 [18]. These provide overviews of pigment use over long periods, but treat manuscript
painting cursorily. They tend to generalize, and treat medieval Europe as if it were a homogeneous
whole. Given the limitations in techniques available for non-destructive analysis at that time, much
of the information in these works was derived from documentary sources, supplemented by visual
assessment. A weakness is the often inadequate detailing of the sources of their information, often
not even indicating whether it is derived from textual sources or analyses. Nevertheless, their
conclusions often come close to current thinking.
More specific, recent and useful are the ongoing Artists' Figments series, at time of writing in three
volumes edited by Feller, 1986, [19], FitzHugh, 1997, [20] and Roy, 1993 [21]. Each consists of a
series of monographs on individual pigments. They summarize and review a wide range of wellattributed material, analytical, archaeological and textual. They also include suggested methods and
criteria for identification for each pigment. They give histories of use, but with insufficient fine
detail for our purposes here. They largely neglect the period AD c. 300-c. 1300. The examples of
analytical identifications of pigment use, 'notable occurrences', are derived from good analytical
practice, but are primarily concerned with painting on canvas and wood, and treat manuscript art
perfunctorily. Unfortunately, many of the analytical techniques and identification criteria given in
this series require samples, so are not always appropriate for manuscripts.
The history and development of pigment analyses
The earliest pigment analyses: visual examination
Attempts have been made to identify the pigments on manuscripts since the late eighteenth century,
but for a long time were hindered by the undesirability of removing samples from miniatures that
were large enough to analyse using the 'wet' chemistry methods of the day. The earliest
examinations of manuscript pigments therefore used visual assessment alone, comparing paint with
a model, mental or painted out, of how various paints look. As Hartley [22] prefaced his
examination of the Book of Kells in 1885: 'For obvious reasons the pigments in question could not
be submitted to any process of chemical manipulation; hence conjecture, judgment, and comparison
were exercised in deciding upon an answer' [22, p. 485]. In 1914 Laurie [23, chapter V] described
and tabulated his visual examination of 60 manuscripts from AD 700-1500, including the
Lindisfarne Gospels, to which he added Kells in 1935 [24]. Laurie, 1914, apparently reports results
obtained solely by microscopic examination of paint in situ [23]. By 1949 he also had a few
samples from manuscripts available for micro-chemical analysis, but does not state which [24, p.
51].
Heinz Roosen-Runge and bis followers
The systematic analysis of manuscript paint may be said to start with the publication by RoosenRunge and Werner in 1960 [8] and Roosen-Runge, 1967, [9] of their examinations of the pigments
and media of Insular and Anglo-Saxon manuscripts. Their method, involving comparison of paint
on manuscripts with reconstructed samples based on contemporary medieval artists' written recipes,
has become standard, although more sophisticated analytical techniques are now employed than the
simple visual comparisons they used. In order to 'evaluate the microscopical appearance of the
pigments', specimens of pigments for comparison were prepared by following approximately
contemporary medieval artists' recipes, and painted out on parchment using egg white (glair), fish
glue (ichthyocollon) and gum.
Roosen-Runge and Werner 1960 [8] examined the pigments and medium of the Lindisfarne
Gospels (c. AD 700) and four contemporary manuscripts. They used visual examination of the
paint, in situ, under a microscope, up to xl 00 magnification. Reflected and transmitted light was
used, as was ultraviolet illumination. Features used for comparison include colour, grain size and
shape, shine, craquelure, transparency and 'fluorescence'. They appear to use the term 'fluorescence'
to describe the appearance of a pigment under UV, regardless of whether actual fluorescence is
taking place. They drew further conclusions based on the characteristic degradation
discolouration of lead pigments. Regarding the media, they state that, lacking micro-samples for
chromatographic analysis, it is 'rather difficult to speak with any degree of certainty'. Roosen-Runge
1967 [9] is a two-volume study of paint materials and techniques in early medieval manuscripts,
developing the techniques described in [8], with special reference to Anglo-Saxon and early English
manuscripts. As before, he made reconstructions, which are the basis for his comparisons. He
hardly discusses the problems inherent in this technique, not acknowledging that as paints age they
will alter their appearance. The preparation of the samples is unfortunately not always adequately
documented. He includes a large number of colour photo-micrographs of pigment reference
samples and sections of manuscripts. He proposed that readers could use these as a tool to make
their own identifications. However, one limitation he did not recognize was that his own
identifications had been made by comparing manuscript paintings with his samples, but those using
the book could only compare manuscript paintings with his photographs.1
The methods of Roosen-Runge are still used. Cains 1990 [26] examined Kells, but 'perhaps with
more caution...I am unwilling to identify pigments...with the same degree of confidence' [26, p.
211]. Cains stated that while he was aware of the superiority of spectroscopic techniques, they were
not available to him, and that he used Roosen-Runge and Werner's technique for want of better. He
also attempted to identify several pigments by the discolouration they have apparently produced in
their neighbours, but with unsatisfactory results. He draws attention to a wider range of possible
organic colours than Roosen-Runge and Werner.
Dormer [27] used these same techniques to examine the pigments on a number of English
manuscripts c. AD 960-1385 in her unpublished dissertation of 1991. She expresses reservations
about the techniques, and notes the problems caused by inconsistencies of medieval pigment
production, and by possible changes of pigment appearance with time [27, p. 107, n. 12], but is
apparently unaware of the limitations imposed by visual comparison and the use of photographs,
since she describes Roosen-Runge's 1967 publication as 'especially useful for reference' [27, p. 49]
and states that his micrographs 'constitute a vital comparative tool.' [27, p. 107, n. 12]. She
concludes that, generally, the drawings under consideration were executed with the same pigments
as fully painted miniatures.
Visual analysis is still commonly used by art historians, often using Roosen-Runge's photomicrographs, but cannot be recommended. Some reasons are given above, and there are others.
Often visual examination amounts to nothing more than a crude estimation of colour and, as visible
spectrometry of pigments shows, there are many examples of pigments that share a colour and
appearance, but which are in fact chemically different. Similatly, one pigment may vary widely in
its appearance. Particle size may totally change the appearance of a pigment. Medieval treatises
abound in recipes for imitating expensive colours such as ultramarine or Tyrian Purple, and these
substitutes can be most convincing to the eye. Furthermore, degradation may change colours out of
recognition. In the words of Cheryl Porter 'You can't tell a pigment by its color' [28].
1
Roosen-Runge 1972 [25] examined the inks of twelfth-century manuscripts using the same
techniques.
Chemical analysis
Roosen-Runge and Werner developed visual examination into an organized system, perhaps taking
it as far as is possible. Historically, after visual examination came tests on small removed samples
using 'classical' wet chemistry, including chromatography, and 'classical' mineralogical testing
under the polarizing microscope.
Analysis of samples
An important advance in manuscript analysis was the work of Flieder in 1968 [6]. She analysed the
pigments and media of tiny samples taken from damaged areas of 40 sixth- and ninth-to
seventeenth-century manuscripts from various origins, using micro-chemical tests, and polarized
light microscopy. She also, unusually, examined cross-sections of illustrations under the
microscope. She used TLC to identify media. She was able to identify media in six manuscripts, all
proteins (e.g. parchment size) before the sixteenth century, the only gums (mainly gum arabic)
being from the sixteenth century. She used Atomic Emission Spectroscopy for some metallic
element identification, and IR for pigment molecular identification. For IR of organic pigments
there were problems with interference from impurities in the pigment itself, from the binders,
substrates and supports, all masking the signal from the colourant, and mixed pigments were also
problematic. Her results are the first analyses of paint on manuscripts that can withstand scrutiny
today.
Another relatively early paper to use reliable, reproducible techniques of standard chemistry was
Orna and Matthews 1981 [1], which examined the pigments on an Armenian manuscript of c. AD
1300, using polarized light microscopy, and micro-chemical tests. Although aware of in situ
techniques, they took samples with a scalpel under a microscope. Where possible, they used
pigment that had offset onto the facing page. They were able to tell that certain red and purple
pigments were lakes by elimination of known mineral pigments, and the presence of the colourless
lake matrix, confirmed by micro-chemical tests [1, pp. 62-4]. Results for certain samples were
checked with XRD.
Analysis without sampling ('in situ' analysis)
Many of the techniques that were used for the earlier analysis of manuscripts - TLC, IR, XRD, MS,
UV-Vis spectrometry of solutions, polarizing light microscopy and micro-chemical tests - require
samples to be taken. Despite the view articulated by Orna and Matthews and quoted above, there
developed a preference for analysing without taking samples, however small. The next major
advance was therefore the development in the 1980s of spectroscopic techniques capable of use in
situ, notably Raman spectrometry.
Techniques that have been used for manuscript paint analysis
A useful review volume is Creagh and Bradley 2000, Radiation in Art and Archeometry [29], which
includes literature reviews for several techniques, including outlines of the principles,
instrumentation, and applications. It discusses techniques for examination of pigments on a variety
of artefacts, including infra-red, ultraviolet, fluorescence, Raman microscopy, Scanning and
Transmission Electron Microscopy, XRF, XRD, EDX and PIXE, although only occasionally with
reference to manuscripts.
Published analyses are discussed below by grouping them by analytical technique, although, as may
be seen from Table 2, often more than one technique is employed. Techniques currently available
will be described briefly, and their suitability, strengths and weaknesses assessed. Most of this
discussion will concentrate on the analysis of pigments, rather than media, gold and parchment.
This reflects the proportion of attention that has been paid to these different materials.
UV-Visible spectrometry
The obvious development of visual analysis is instrumental measurement of visual properties; the
visible property most characteristic of a pigment being its colour. This may be done either in
reflection, where light is bounced off an artefact then measured, or in transmission, where it is
passed through a removed sample, usually in solution. There are also various colorimetric
techniques. Spectra show the transmission or absorption of UV-visible light of a sample at different
wavelengths or frequencies. Pigments are identified by 'fingerprinting', that is, by comparing the
spectra of samples with those from samples of known composition.
UV-Vis in reflection
Fuchs and Oltrogge 1994 [30] examined the pigments on the Book of Kelts and 12 other Insular
manuscripts, c. AD 700 — c. 800. Only portable instruments could be used, presumably as curators
were reluctant to have the manuscripts moved to a laboratory. A microscope and a visible-light
reflectance spectrometer (with a 3 mm spot diameter) were chosen.
'With these instruments a number of medieval colour materials can be identified with certainty and
others can be determined with some probability...A few materials cannot be analysed with portable
machines but would need [other] non-destructive methods [XRD and IR]' [30, p. 133].
The authors are careful to repeat this caveat periodically. They talk of UV-visible spectra showing
'a certain conformity' but warn that this is 'not conclusive enough' [30, p. 138]. 'If materials have
[deteriorated] too much...analysis becomes extremely complicated and sometimes impossible' [30,
p. 133]. Spectra from many reference samples, amounting almost to a reference library, are given.
Guineau et al. 1996 [31] examined the pigments on seven French and Norman ninth- to eleventhcentury manuscripts using UV-Vis in situ, and using Raman, IR and XRD on small samples. UVVis was used to distinguish between red haematite and vermilion. The authors used colour
measurements (L*a*b*) of green pigments as a basis for grouping manuscripts. Guineau et al. 1996
[32] examined the blue ink on two ninth-century manuscripts using UV-Vis. Indigo was detected.
Guineau et al. 1993 [33] examined the pigments on two fifteenth-century Italian manuscripts using
Visible spectra. A fibre-optic probe was used for in situ examination [33, p. 125]. Colorimetric
measurements were also used. Guineau et al. 1998 [34] examined the pigments on one fifteenthcentury French manuscript using UV-Visible and XRF. Best, Clark and Daniels 1995 [35] and
Montalbano 1998 [36] also use UV-Vis in reflectance.
Table 2. Analytical techniques cited in selected references
Table 2. Analytical techniques cited in selected references (continued)
UV-Vis in transmission
This has been used with some success for organic pigments, notably red lakes. It has been used for
dry samples of cross-sections of paintings by Kirby [37] and by Wallert for samples taken from
manuscripts and put into solution [10, 38, 39].
Wallert 1986 [38] describes the use of UV-Vis in solution, XRD and IR for identifying organic red
pigments, especially brazil, on three fifteenth-century Italian manuscripts. A number of reference
spectra are reproduced. The nature of the inorganic substrate of the organic pigments was
determined to be calcium carbonate, using XRD, EDX and micro-chemical analysis. Wallert 1989
[39] examined the colouring of parchment sheets, especially purple. Analysis of reconstructed
samples was tried using UV-Vis in solution, and 3DF of removed samples in solution (see below).
One small sample of a fifth-century purple codex was examined, and was determined to have been
dyed with Alkanna tinctoria L. Wallert 1991 [40] concentrates on the identification of 'cimatura di
grana' (a lake made by extracting the colourant from dyed clippings of cloth) on samples removed
from manuscripts using these same techniques.
Microscopy of removed samples — Cross-sections
Manuscripts generally have less complicated layer structures than other forms of painting, and there
is not the same need to examine layer structure. Combining this with restrictions on sampling has
meant that the taking of cross-sections is almost unknown. An exception is Orna and Matthews
1981 [1], A new technique for examining cross-sections by drilling a tiny cylinder through the
thickness of the parchment has been developed by Fredrickx, Wouters and Schryvers [41]. These
samples are then examined using Transmission Electron Microscopes, in which Electron Diffraction
and EDX analysis may be performed.
Microscopy of removed samples - individual pigment samples
Conventional mineralogists' tests have been adapted for use on individual particles of mineral
pigment. Particles are mounted in a medium, such as gum or 'melt-mount', and mounted on a
microscope. Two polarizing filters are used, above and below the sample stage. Light is shone from
below, through the polars and the sample. Minerals exhibit characteristic phenomena, e.g. shape,
crystal shape, particle size and opacity, and they rotate the plane of polarization of transmitted light
in characteristic ways, which may be observed as coloured patterns against the dark background of
crossed polars. The refractive index may be determined, and several crystal properties. These
properties are compared with those of known minerals. It is a very effective technique for inorganic
mineral pigments, but cannot be carried out in situ. A good summary of this technique is given in
Feller 1986 [19, pp. 285-98]. It remains a standard technique for examining pigment samples taken
from other, non-manuscript, painted surfaces. It is only really useful for inorganic pigments. The
results can be checked in case of ambiguity by other techniques, including those that use samples,
e.g. micro-chemical tests.
Quandt and Wallert 1998 [42] examined the pigments, binding media and the grounds under gold
leaf, on a thirteenth-century Byzantine manuscript using XRF, polarized light microscopy, XRD,
EDX and MS. Samples were used. Where possible, they used pigment that had offset onto the
facing page. Elemental analysis of a yellow sample using EDX detected aluminium, silicon,
potassium and calcium, 'components of the materials used to co-precipitate pigment lakes from
natural organic colourants.' Micro-chemical tests for carotenoids were tried. Fluorescence analysis
was tried for a yellow and a purple organic pigment. Saffron was suggested, and was confirmed by
MS, and for the purple, dragon's blood. Binding media were analysed using MS, and gum arabic
found (beeswax was found in one sample but attributed to a candle splash).
Micro-chemical tests
These are conventional 'wet' chemistry tests that may be performed on minute samples, under a
microscope. Typically they involve adding a reagent liquid, which produces a colour change or a
fizzing or some other visible phenomenon. For example, tests exist to detect certain ions present in
pigment compounds, such as sulphur, iron, or copper.
Since Laurie 1949 [43], when samples are taken for examination (e.g. for polarized light
microscopy) it has been common also to apply micro-chemical tests, which can distinguish between
otherwise similar pigments. Tests are described and illustrated throughout Feller 1986 [ 19],
FitzHugh 1997 [20] and Roy 1993 [21].
Infra-Red spectrometry (IR) and Fourier-Transform IR spectrometry (FTIR)
IR spectrometry is in general principle the same as UV-visible spectrometry, in that the absorption
or transmission of a sample is measured, only this time in the infra-red region. Different molecules
have different IR spectra. It is possible to match certain chemical functional groups to certain
spectral peaks, but in the case of pigments these are usually common to a wide range of pigments,
so are rarely useful, and so for our purposes IR is generally used as a fingerprinting technique.
Fourier-Transform IR spectrometry (FTIR) is a computer-assisted form of spectrometry, where a
number of spectra of the same sample are taken and one improved spectrum is calculated from
them. It is more sensitive than conventional IR, and improves the signal-to-noise ratio, that is, it can
distinguish weak peaks against 'noisy' backgrounds.
Infra-red spectrometry has, for manuscripts, generally been used as one of a number of
complementary techniques, rather than alone. A library of IR spectra of natural organic colourants
is given in Schweppe 1992 [44]. Burandt 1994 [45] discusses the use of FTIR and XRF for
identifying drawing inks. XRF can detect iron, indicating iron-gall ink, but iron may also be present
in inks prepared with iron utensils (and may also be present in paper). FTIR spectra of iron-gall
(gallo-tannic) ink closely match library spectra of tannin. Pure carbon has no FTIR spectrum, so any
spectrum is caused by the binding medium only.
Infra-Red False Colour photography (IRFC) and NIR visualization
IRFC uses a special film to photograph artefacts. The film is sensitive to the Near Infra-Red region
(NIR) - 780-3000 nm wavelength - as well as the visible region. Using this film, characteristic NIR
reflectance or absorption can be detected. This has been found useful for distinguishing between
pigments that have extremely similar visible spectra, i.e. which are almost the same colour.
Certain authors have claimed the ability of IRFC to distinguish a variety of pigments. It is becoming
apparent, however, that authors disagree on which 'false colours' are given by which pigments. The
history and debate is summarized and discussed in Clarke and Meijers 2000 [46] and need not be
repeated here, but the conclusion is that it appears that IRFC may really only be reliable for blues.
Porter 1997 [47] examined the blue pigments on five twelfth-century English manuscripts, using
IRFC. Her aim was to see if ultramarine was used on English manuscripts as early as the twelfth
century. Ultramarine was indeed found. While recognizing that IRFC cannot provide information as
detailed as is possible with instrumental analysis, she praises it as 'inexpensive, highly portable and
nondestructive'. Meijers 1999 [48] examined the blue pigments on one fifteenth-century English
manuscript using IRFC, finding azurite and almost certainly ultramarine. The findings paralleled the
stylistic differences between the various miniaturists who worked on the manuscript, and patterns
could be determined in the use of blues linked to the stages of execution. Electronic NIR
visualization devices may be used instead of IRFC, and give 'real-time' results, as described by
Clarke and Meijers 2000 [46]. A good recent paper, which plausibly discusses pigments other than
blues is Singer and Cahaner 1999 [49].
Chromatography
Chromatography, as its name suggests, has been found highly suitable for distinguishing dyes, but it
requires samples. A sample is dissolved in a solvent and allowed to pass slowly through some
porous medium, e.g. filter paper or powder packed in a tube. Different materials will migrate
through this medium at different rates in any given solvent. By comparing the times taken to move,
unknowns may be compared with knowns. Chromatography remains one of the few techniques
capable of analysing media, e.g. see Wallert 1991 [10].
Thin Layer Chromatography (TLC)
The simplest form of Chromatography is TLC, where a plate is coated with a powder. Spots of
sample are placed at one end, and that end immersed in solvent. More complex are High
Performance Liquid Chromatography (HPLC) where the plate is replaced with a packed tube
('column') of powder, and the solvent is pumped through.
The classic work on TLC of historical natural organic colourants is Schweppe 1992 [44], which
reproduces many TLC plates in colour. Masschelein-Kleiner and Heylen 1968 [50] discussed
methods of analysing samples of red lakes, using UV-Vis (in solution), IR and TLC. They analysed
two samples from manuscripts, one twelfth-century, one fifteenth-century, using TLC, finding
madder. They remarked that, at that time, the samples from the illuminations of manuscripts necessarily parsimonious - are at the limit of what it is possible to identify among natural
colourants, and that for this type of specimen, only TLC was effective in a few favourable cases.
High Performance Liquid Chromatography (HPLC)
HPLC has been used successfully to identify natural organic colourants on textiles from minute
samples, gradually replacing TLC. Jan Wouters' work is particularly distinguished, especially for
the minute samples that have been analysed. See Karmos et al. 1995 [51]; Wouters 1985 [52], 1989
[53], 1991 [54]; Wouters and Verhecken 1989 [551; Vest and Wouters 1999 [56]. Vest and
Wouters 1999 |56| examined the dyes and pigments used on the alum tawed bookbinding 'leather' of
54 twelfth- to eighteenth-century books, using HPLC and EDX. They found indigo/woad, lac,
madder, buckthorn, iron-tannin (black) and brazil dyes, and an artificial copper green applied as a
pigment2.
In 2000, Fredrickx, Wouters, et al. began work on HPLC of organic pigments on manuscripts using
samples drilled out using a 0.1 mm diameter biopsy needle [41].
Mass Spectrometry (MS)
A sample is introduced into the instrument and is volatilized by a vacuum. The molecules are then
ionized by a beam of electrons and become electrically charged. A series of electromagnets then
accelerate these ions into a beam. Further electromagnets create a field perpendicular to this beam,
which deflects it. Ions of different mass (strictly, of different mass-charge ratio) are deflected by
different amounts by this field, much as a bullet and a cannonball would be deflected by different
amounts by hitting them with a bat. The deflection is measured, and provides a spectrum of the
masses of ions present. These masses may be compared with masses of expected molecules or
molecule fragments. MS has been used as a complementary technique for removed samples,
particularly for the identification of media by Mills and White 1982 [57] and 1994 [58], but also for
organic pigments by Quandt and Wallert 1998 [42].
Energy Dispersive X-Ray analysis (EDX or EDAX)
As XRF, this is an elemental analysis technique, not a molecular one, so is best suited to inorganic
analysis. The sample to be analysed is placed in a vacuum chamber (EDX instruments are
commonly situated inside electron microscopes) and a beam of electrons is directed at it. The
energy of the electron beam displaces electrons from the atomic shells, and these displaced
electrons are detected, and their energy measured. Electrons from each shell of each element have a
characteristic energy. The elements present can therefore be determined. EDX has been used to
confirm the identity of inorganic pigments, e.g. Wallert 1991 [40], Vest and Wouters 1999 [56], and
also to identify the substrate of organic lakes, e.g. Wallert 1986 [38] and 1991 [40].
X-Ray fluorescence (XRF)
X-Ray fluorescence is the same phenomenon as UV-Visible fluorescence, but at a higher energy of
electromagnetic radiation. X-rays are used in place of light. Fluorescence (of lower energy X-Rays)
is detected and a spectrum plotted. XRF is an elemental analysis technique, not a molecular analysis
one, as each element has a characteristic XRF spectrum, regardless of its molecular environment. It
cannot be used for elements of low atomic mass, and is therefore primarily useful for inorganic
analysis. XRF instruments are commonly included in electron microscopes. It has typically been
used in combination with fingerprinting techniques such as Raman.
XRF instruments that may be used in situ do exist. Cesareo 1996 [59] and Devezeaux de Lavergne
et al. [60] examine the pigments, gold and inks on one thirteenth-century manuscript in French,
using Raman microscopy and XRF. XRF was used as a preliminary to determine which pigments to
examine with Raman. However, in common with most 'open-air' XRF instruments, the sample area
is very large. In these cases, an area 16 mm in diameter was analysed, so was only useful for
preliminary surveying of 'zones', and for the detection of true gold. Klockenkämper et al. 2000 [2]
discussed XRF as a technique for analysis of samples of inks and pigments, including those on
manuscripts, and gives the same c. 1510 Antwerp example as was reported in Denoel 2000 [61] and
Dekeyzer et al. 1999 [62]. Small samples were removed with a swab. It was possible to distinguish
three hands using iconographic classification, and this identification was confirmed by XRF.
De Reu et al. 1999 [63] suggested that an attempt be made to use XRF to analyse the gold leaf and,
since leaf was often made from beaten coins, to relate it to coins of known origin. This would be
interesting, but would be fraught with problems consequent on extensive gold reuse and the long
life and wide circulation of gold coins.
X-Ray Diffraction (XRD)
Further crystallographic details may be obtained by XRD. A sample is placed in the path of an Xray beam. The atomic lattice of the crystal diffracts the path of the X-rays, with the angle of
diffraction depending on the atomic spacing in the lattice. The diffracted X-rays are recorded on
either film or by a detector. Again, known compounds are compared with unknown. Conventional
XRD requires samples, see Guineau et al. 1986 [64] and Wallert 1991 [10]. However, Fuchs and
Oltrogge 1992 [65] examined the pigments on one manuscript, the fifteenth-century Gottingen
Modelbook, using XRD in situ. They used modified equipment that suspends a manuscript page in
the path of the X-Ray beam. The only other authors to have published the use of XRD in situ are
Nir-el and Broshi 1996 [66]. They examined red ink on the only four fragments of the first-century
BC Dead Sea Scrolls where it was used, using XRF and XRD, finding it to be cinnabar. XRD in
situ was possible due to the small size of some of the fragments, allowing them to be placed in a
standard instrument as though they were conventional (if very large) samples.
Fluorescence spectrometry and 3DF
Certain materials fluoresce under ultraviolet, e.g. well-aged picture varnish, and a number of
organic pigments (the well2
These results are for coloured bindings, not miniatures, so are not included in Table 3.
known example being genuine rose madder) and simple broad-spectrum hand-held UV lamps have
long been used to identify the presence of these. Roosen-Runge described the appearance of
pigments under a broad-spectrum hand-held ultraviolet lamp, including fluorescence phenomena [8,
9]. This has been refined into the molecular fingerprinting technique of Fluorescence spectrometry.
A beam of light, ranging from UV to visible, is directed at or through a sample. The light reflected
or transmitted is recorded and, if the sample is fluorescent, the emitted fluorescence appears on the
spectrum. Fluorescence of a particular material is characteristic; there is a specific wavelength of
incident light ('exciting beam') that will cause the maximum fluorescence intensity, and that
fluorescence ('emitted beam') is also of a characteristic wavelength. Conventional fluorescence
spectrometry holds either exciting or emitted wavelength constant and scans the other, producing a
curve and has been published by Guineau 1989 [67], Guineau and Vezin 1990 [68] and Wallert
1991 [40].
'3-Dimensional' Fluorescence spectrometry varies both wavelengths, producing a series of curves,
which are combined to form a 3-D surface, which may be presented as a contour map. The point of
maximum fluorescence therefore appears as a peak with coordinates of exciting/emitted
wavelengths. 3DF was introduced in Wallert 1991 [10]. Removed samples of pigments were
examined using polarizing light microscopy, micro-chemical tests, EDX, and XRD for inorganics,
and UV-Vis and 3DF for organics. Media were examined using 3DF and TLC. Wallert's analysis
demonstrated a correspondence between the illuminations and the recipe books. He stated that this
was the first time 3DF was used for works of art, although see Wallert 1989 [39] in which he
examined the colouring of purple dyed parchment. Analysis of reconstructed samples was tried
using UV-Visible in solution, and 3DF of removed samples in solution. The 3DF spectra are
unfortunately presented in a stereo projection, rather than as contour maps, which makes
comparison between spectra extremely difficult.
Wallert 1991 [40] analysed samples of 'cimatura di gratia' removed from manuscripts. EDX was
used for the inorganic substrate and fluorescence spectrometry, both conventional and 3DF, of
samples in solution for the organic component. Quandt and Wallert 1998 [42] tried fluorescence
analysis for a yellow and a purple organic pigment. Saffron was suggested, and was confirmed by
MS. The theory and application 1999 of 3DF to date is reviewed in Clarke [69]3.
There are considerable problems with fluorescence analysis of organic paints on parchment, notably
the weak fluorescence of many pigments, the strong, broad-band fluorescence of parchment itself,
and the extreme variability of peak position depending on exact recipes, pH, concentration and
substrate.
Particle Induced X-ray Emission (PIXE)
PIXE is also an elemental analysis technique, and also measures the characteristic energies of
emitted X-rays. It may be used in situ, but requires a massive installation, including a particle
accelerator. Where one is available it may be used for elemental analysis in a manner analogous to
EDX. A beam of protons from the particle accelerator is aimed at the artefact to be analysed. Much
as in EDX, X-rays are emitted and are analysed.
One of the earliest applications of PIXE was the examination of the inks and papers of incunabula
by Cahill, Kusko and Schwab 1981 [70]. The configuration of their instrument requires the sample
page to be sandwiched between two sealed halves of a vacuum or helium chamber, and so is clearly
unsuitable for delicate illuminated manuscripts They found PIXE to be highly sensitive and capable
of providing quantitative as well as qualitative results. Further quantitative results for the printing
inks and papers of incunabula are given in Cahill et al. 1984 [71] (using PIXE) and Mommsen et al.
1996 [72] (using XRF). A good, illustrated description of the use of PIXE for manuscripts is del
Carmine et al. 1993 [73].
Canart et al. 1993 [74] examined inks on three eleventh-century Italian manuscripts using PIXE for
quantitative elemental analysis. In particular, the proportions of potassium, iron, copper and zinc
were found be characteristic for each manuscript examined. Good consistency was found for inks in
any one manuscript, and a reasonable distinction between manuscripts was also found. Reasons for
these differences were not obvious. This article is good on the practice and problems of PIXE
analysis of works on parchment.
Denoel et al. 1999 [75] examined the pigments on one sixteenth-century Flemish manuscript using
PIXE. They noted that when vermilion was detected, the amount of phosphorus increased. They
examined egg yolk with PIXE and found phosphorus to be its 'main component', suggesting that
egg yolk medium was used with vermilion. Denoel 2000 [61] examined the pigments on one
sixteenth-century Flemish manuscript using PIXE and Raman microscopy. She pointed out that
green paints are always difficult to determine using Raman analysis due to the complexity of green
mixtures used and also owing to the difficulty of identifying green pigments, presumably because of
the huge range of possibilities4.
Raman spectrometry and Fourier-Transform Raman spectrometry
Raman is similar to IR and FTIR in that it analyses the IR portion of a material's spectrum, and it is
used for molecular fingerprinting. A laser is aimed at the particle to be examined and the Raman
shift, caused by characteristic molecular vibrations (somewhat analogous to a Doppler shift for
sound) is recorded as a spectrum. It is particularly useful as the laser may be directed, using
microscope optics, even to a single pigment grain, and using fibre-optics it may be directed at paint
samples'in situ. In consequence, it has become widely used, almost standard practice, for pigments
on manuscripts. Confocal microscopes may also be used, which allow examination within a narrow
depth of field, so that a series of profiles at different depths may be carried out, under ideal
circumstances.
Guineau 1984 [76] discussed the analysis of azurite and malachite in situ by Raman microscopy,
giving the example of one fifteenth-century French manuscript. This work was reviewed in Vezin
1984 [77]. Guineau et al. 1986 [64] examined the blue pigments on samples (10-50 |im) taken from
six twelfth-century manuscripts from Corbie, France, using microscopy, XRD, IR and Raman
microscopy. All the samples were found to be ultramarine.
3
A number of applications of 3DF have been tried on textiles, and on Ukiyo-e prints by Shimoyama
and Noda. See Dyes in History and Archaeology vols. 12, 13 and 15, and Clarke 1999 [69] for a
bibliography.
4
See also [2] and [62], which report the same set of analyses of this manuscript.
Best, Clark and Daniels 1995 [35] examined pigments on one Icelandic fourteenth-century
manuscript using Raman microscopy and reflectance UV-Vis-NIR spectrometry, suggesting that the
two techniques 'are best used in a complementary fashion' [35, p. 38]. With Raman they were able
to achieve a spatial resolution of l µm, sufficient to identify a single pigment grain - invaluable in
the analysis of mixtures. Clark and Gibbs 1998 [78] also examined pigments on one thirteenthcentury 'Byzantine/Syriac' manuscript using Raman microscopy.
Raman has generally been found satisfactory for inorganic pigments, but has frequently been found
unsatisfactory for organic pigments. Guineau and Guichard 1987 [79] described the use of Raman
micro-spectrometry to identify natural organic colourants in situ, and identified madder on the
headband of a thirteenth-century Islamic manuscript. The spectra were extremely noisy, due to
fluorescence interference, making positive identification dependent on knowing what might be
there, and then looking carefully for the expected peaks. The matches as printed do however appear
to be reasonable, and do not require an act of faith. Burgio, Ciomartan and Clark 1997 [80]
examined pigments on three miscellaneous fourteenth- to fifteenth-century manuscripts using
Raman microscopy. These manuscripts were apparently chosen for convenience of access, being at
University College London, where the laboratories were also situated. The gold paints were also
examined, to determine if they were mosaic gold (SnS2), which they were not. This paper is notable
for the claimed detection of the organic pigment kermes and for the identification of an amorphous
carbon pigment as ivory black. Clark and Gibbs 1998 [81] examined pigments, in this case on three
sixteenth-century Indian manuscripts, using Raman microscopy in situ. This paper is notable for the
use of portable 'Remote Laser' Raman instruments, which use a fibre-optic probe to deliver the
exciting beam to the artefact, and collect the scattered beam. This removes the size restrictions of
the artefacts to be examined, as they no longer have to fit on a microscope stage.
Raman analysis of micro-samples
A recent development is the examination of tiny samples. Almost invisibly small samples, of
approximately l µg, are taken, by gently rubbing the surface with a small dry cotton swab. [3, 4]
Vandenabeele et al. 1999 [5] examined micro-samples of pigments from a late fifteenth-/early
sixteenth-century Flemish manuscript using XRF and Raman microscopy. They conclude that
Raman and XRF make a good combination, the Raman allowing the analysis of single pigment
grains, and the XRF providing quantitative elemental information to substantiate the Raman results,
which should, in future work, allow impurity patterns to be established and to be used as a
fingerprint. As Table 2 shows, this combination has become popular.
Coupry 1999 [7] analysed 98 samples taken from nine eleventh- to twelfth-century Norman
manuscripts, using Raman microscopy. Her samples were typically 1/100 mm and, where possible,
were taken from areas of damage. She found indigotin, perhaps from woad (Isatis tinctoria L.) in
one late tenth-century manuscript, and minium, calcite, lapis lazuli, vermilion, lead white and
orpiment. She suggested that there was a genuine break c. AD 1000, with the introduction of lapis
lazuli, and that also in this period minium was gradually replaced by vermilion (see also 82).
Raman vs. IR
Unfortunately water and carbon dioxide, present in the atmosphere and in manuscripts, produce
strong, broad IR spectra that swamp the details of pigment spectra. CO2 has no Raman spectrum,
and that for water consists of narrow distinct bands. IR is a technique used primarily in
transmission, and IR microscopes rely on the IR beam passing through the sample, e.g. a pigment
grain on a microscope slide, which is clearly inappropriate for manuscripts. In the case of samples
too thick for this, such as manuscripts, the beam passes through the sample, and is reflected by the
substrate. A relatively non-reflective surface, such as a manuscript, is unsuitable. Raman
microscopes do not suffer from this problem, as the sampling beam is re-emitted from the sample,
and so may be collected at 360°. Furthermore, IR microscopes are not constructed with stages
sufficiently large to accommodate a manuscript.
Underdrawings, hidden layers and effaced writing
For easel paintings it is common to take small samples of cross-sections to help to determine the
arrangement of the paint layers, and X-Ray photography may also be used. Miniatures do not
usually have the same complicated series of layers of an easel painting, so these techniques are not
used, although see the reference above to the micro-drilling techniques of Fredrickx et al. [41]. The
only layering that is commonly present (excluding the bole under gold) is underdrawing, in some
carbon-based medium. Carbon absorbs infra-red strongly. Many materials that are opaque to the eye
are transparent to infra-red, including many paints. Underdrawing may be photographed using an IR
'light' source, and IR-sensitive film. Today it is more common to use electronic video imaging
devices. The old 'Vidicon' is increasingly replaced with charge coupled device (CCD) cameras,
which often allow real-time viewing; see Delaney et al. 1993 [83], Kossolapov 1993 [84],
Walmsley et al. 1991 [85] and 1993 [86].
Similar techniques may be used to reveal writing that is difficult to read. Inks may fade
considerably in the visible region, or the supports (papyrus, leather, parchment or paper) may
darken through age, dirt or fire damage, such that the writing is all but invisible to the naked eye.
Viewing in transmitted light may sometimes help. A simple, widely used technique for parchment
is to use a hand-held ultraviolet lamp. The parchment fluoresces but any residual ink (especially
iron-gall ink) will quench this fluorescence, and so appear darker against a lighter background.
A more sophisticated approach is the use of band-pass filter reflectography, in which the writing is
illuminated with light in a series of narrow spectral bands, from ultraviolet to near infra-red, and the
image viewed through a video camera that is sensitive throughout this spectral region. At certain
wavelengths the contrast between the support and the ink will be greater than it is under normal
viewing conditions, due to the relative differences in their UV-Vis-NIR absorption. This can also
reveal hidden layers and underdrawing. Band-pass reflectography will also to some extent
discriminate between inks. Vegetable inks are only visible at wavelengths shorter than 700-750 nm,
and iron-gall inks shorter than 1200-1400 nm, while carbon inks are visible to the limits of IR
visualization, around 1900 nm (see Fuchs and Oltrogge 1997 [87]). The most useful collection of
recent papers on reading effaced writing is that edited by Fossier and Irigoin 1990 [88].
Parchment species
For many years, identification of parchment species was carried out by sight or feel. Some incorrect
diagnoses of calf, sheep or goat inevitably followed. Coupled with inconsistencies in the use of the
terms 'parchment' and 'vellum', the work of many industrious authors unfortunately cannot be
depended on.
Federici et al. 1996 [89] carried out histological studies on parchment. Examination of crosssections allowed distinction between sheep, goat and calf; however, the taking of cross-sections
from manuscripts is clearly unacceptable. A simple non-destructive method of determining
differences in species by examining the grain pattern (the pattern caused by follicle arrangement)
has been suggested. The literature on this technique and on the results of its application to
manuscripts is reviewed in Federici et al. 1996 [89]. Surface illumination, at xl5-20 magnification
works satisfactorily for leather, but less well for the less clear follicle patterns of parchment.
Follicle patterns are obscured in parchment as much of the grain layer is scraped away in its
processing. To overcome this, Federici-et al. used light transmitted through the parchment. The
light was delivered using fibre-optics to protect the sample from heat. They found the follicle
pattern to be most noticeable at the spine of the animal, which often corresponds to the spine of a
book, where a bifolium is folded.
Deoxyribonucleic acid (DNA) analysis is often impracticable, due to deterioration of DNA with
age, coupled with contamination from centuries of handling. To reduce the influence of
contamination, sample size needs to be increased to an unacceptable size. DNA analysis has
however been carried out on the Dead Sea Scrolls. Woodwards al. 1996 [90] analysed early modern
parchment and leather bindings, and archaeological hide and leather, to establish the species of
origin by mitochondrial (mtDNA) sequencing and to identify the individual animal. This is useful
for text reconstruction as isolated fragments of manuscripts may be reunited if their DNA shows
them to be from the same animal. Further papers on the application of these techniques appear in
Parry and Ulrich 1996 [91].
Again, due to contamination through centuries of use, radiocarbon (14C) dating of parchment, even
using the highly sensitive technique of Accelerator Mass-Spectrometry (AMS), requires samples of
about 15 x 15 mm. Smaller samples have rarely been dated successfully. Often a radiocarbon date
can only be assigned with a standard deviation of 35 years (i.e. ± 35 years) or even ±100 years, e.g.
after c. AD 1500 or for very small samples. Successes include the Dead Sea Scrolls [92] and the
Vinland Map [93].
Conclusions
The amount of analytical work done has increased recently, as increasingly sensitive and
unambiguous techniques are developed. An ideal technique would be:
- Non-destructive. The technique should not require samples to be taken, and should do no other
damage. The physical integrity of an artefact should be respected where possible. A compromise
has often been the avoidance of visible damage, for example in the taking of micro-samples.
- Capable of identifying a completely unknown material.
- Universal (capable of identifying any material).
- Sensitive to very small samples, or to very small traces in larger samples. Pigment grains may
be as small as 0.5 nm across and weigh a few picograms.
- Specific, i.e. be able to distinguish unambiguously between similar materials.
Immune from interference (from media, mordants, substrates etc.).
Be capable of identifying components of mixtures.
- Capable of good spatial resolution, to allow analysis of small adjacent areas of colour without
interference from fields, and to distinguish individual pigment particles in a mixture.
- Portable, such that valuable artefacts need not be transported.
- Fast.
However, no technique that has been published is yet ideal, and particular problems remain in the
analysis without sampling of organic pigments, mixtures and media. There is no single 'magic
bullet', but when more than one method of analysis is used, the weakness of any given technique
may be complemented by corresponding strengths in another. Typically, fingerprinting techniques
(UV-Vis, Raman and IR spectrometry), which with the dilute and small samples common on
manuscripts can often give weak or ambiguous peaks, is complemented by the highly sensitive
elemental analysis techniques of XRF, EDX and PIXE.
The choice of equipment often simply depends on availability, as does the choice of manuscripts to
examine. PIXE is a good example; it would be unimaginable to purchase a PIXE installation simply
to carry out elemental analysis of manuscripts, when XRF is far simpler, cheaper and more portable,
but if it is available, it can make more sense to use it. The overwhelming problem still remains that
of getting equipment and manuscripts together in the same room - the equipment is often too big,
and the manuscripts often too valuable, to be moved. Much published research has been determined
by these considerations. Now that Raman equipment is becoming 'portable' (in the sense that it can
be moved, with difficulty), more and more Raman analysis is being carried out and more may be
expected. Often research has been driven by someone who has access to equipment and has a
research 'itch', so examines whatever manuscripts are available; less often is it initiated by a curator,
who may have difficulties in getting authorization to move manuscripts. To date, the main
application of analysis has been motivated by art historical or codicological considerations, rather
than by those of conservation.
Summary tables
The findings of the reports outlined in this paper are most conveniently presented in the form of
tables. Any critical evaluation of published results depends largely on criticism of the techniques
themselves. Some techniques provide very certain results, others are highly ambiguous. Since the
technique used is such an important determinant of the reliability of results, the techniques that were
cited in the references are given in Table 2. The pigments reported as present are summarized in
Table 3.
Table 3. Pigments cited in the references
Table 3. Pigments cited in the references (continued)
References
References 94-100 are not referred to in the text above, but their results are incorporated in Table 3.
1
Orna, M.V. and Matthews, T.F., 'Pigment analysis of the Glajor Gospel book of U.C.L.A.',
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57-72.
2
Klockenkamper, R., von Bohlen, A. and Moens, L., 'Analysis of Pigments and Inks on Oil
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3
Vandenabeele, P. and Moens, L., 'Application of Micro-Raman Spectroscopy to the
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laboratoire: Premier colloque interdisciplinaire de I'Universite de Liege, Le Vertbois, LiegeBelgique, 2000, (unpublished poster).
4
Wehling, B., Vandenabeele, P., Moens, L., et al., investigation of Pigments in Medieval
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5
Vandenabeele, P., Wehling, B., Moens, L., ct al., 'Pigment investigation of a late-medieval
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1999, pp. 169-72.
6
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7
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Author
Mark Clarke trained in paper conservation at Camberwell College of Arts, London, and in
Conservation Science at De Montfort University, Lincoln and Leicester, and completed a doctorate
on Anglo-Saxon Manuscript Pigments at the Department of Archaeology in the University of
Cambridge. His interests are the history of artists' technology, medieval artists' 'recipe books', the
study of works of art as physical objects, and the development of non-destructive techniques of
analysis for pigments. He is currently a guest researcher at the Instituut Collectie Nederland,
Amsterdam.