chapter 14.pdf

Chapter 14 

Pigment identification in illuminated 

manuscripts 

Peter Vandenabeele and Luc Moens 

14.1 INTRODUCTION 

Throughout history, books, being symbols of wisdom, have always attracted 

people. Numerous mediaeval paintings show marvellous illuminated manuscripts, 

expressing the importance of their owner. Only the wealthiest people 

in the society could afford books. Indeed, apart from the time invested to 

manufacture a manuscript, even the raw materials needed were highly 

expensive [1,2]. The number of bifolia that could be obtained from a single 

sheet of skin, though depending on the size of the book, was limited; 

parchment and pigments were very expensive. Some manuscripts contain 

colourful miniatures, capitals or border illuminations, raising the cost of the 

manuscript. 

While admiring these codices, one almost automatically wonders about the 

production process of these artefacts. How were these works manufactured? 

How many people worked on this book? Who were they and how long did it 

take to make such a manuscript? These questions are not always simple to 

answer, and the solutions might depend on the work under consideration. 

Manuscript production starts with the purchase of different raw 

materials: parchment, pigments, binding media, etc. Depending on the 

book and its size as ordered, an estimation of the number of folios was made. 

Decisions were taken on the number, size and position of the different 

miniatures and the layout of the work was discussed. Subsequently the 

sheets of parchment were cut into the desired format and folded into a 

bifolium (or diploma). A number of these were gathered together into a quire. 

Often a quire consisted of four bifolia, thus containing eight folios (or leaves), 

i.e., 16 pages. The next stage in manuscript production was the ruling of the 

pages. Lines were drawn in order to determine the layout of the page. Then 

the scribes copied the text by hand. Spare room was left for later insertion of 

Comprehensive Analytical Chemistry XL 

Janssens and Van Grieken (Eds.) 

© 2004 Elsevier B.V. All rights reserved 635

P. Vandenabeele and L. Moens 

miniatures, capitals, paragraph marks, etc. During the long and labourintensive 

process of copying the whole treatise, occasionally mistakes were 

made. In this case the scribe marked the alterations in the margin. Similarly, 

the scribe made markings for the rubricator, who inserted capitals and 

headings in the next stage of manuscript production. The word "rubricator" 

originates from the Latin "rubrum" which means "red," a colour that is often 

used for capitals, titles, etc. At the end of many manuscripts a "colophon" can 

be found: this often indicates the year of manufacture or purchase and the 

patron. The whole manufacture of mediaeval manuscripts was a very labourintensive 

and time-consuming process. Occasionally, in some manuscripts a 

"lamentatio" can be found in which the scribe complained about the work it 

took to copy the whole manuscript. Examples of these are [2]: 

Explicit hic totum, frater Jacobe, da michi potum 

(This is the end of my duty, brother Jacob, bring me a mug of wine) 

or 

Finito libro, frangamus ossa magistri 

(As the copying of the manuscript is finished, we will break the bones of the 

master, who composed it) 

Generally, many mediaeval manuscripts have survived the ravages of 

time quite well. One reason for this phenomenon is that these works of art 

have always been considered as very valuable and thus have been handled 

with care. Often manuscripts were status symbols instead of utilitarian 

objects. Codices were kept in libraries, and thus were protected at least from 

some external influences. Manuscripts were stored closed, shielding the 

illuminations from harmful influences, such as light. On the other hand, one 

can note that there is also a kind of historical selection: works of art of bad 

technical quality are often eliminated in the course of time, so that mainly 

works of good technical quality remain. 

14.2 COMBINED METHOD APPROACH 

There are several possible reasons to perform art investigations [3]. Aside 

from the fundamental interest in ancient materials and techniques, art 

analysis can help in solving specific questions of (art-) historians, curators 

and restorers. These professionals often encounter problems concerning 

degradation, authenticity or provenance of an artefact. Degradation studies 

are made by looking at changes in the structure and the spectroscopic 

characteristics of the different components. The question of authenticity is 

closely related to that of dating the artefact. Painted objects of art can be 

636

Pigment identification in illuminated manuscripts 

approximately dated by examination of their pigments. Certain pigments 

have well-established dates of invention and finding them indicates a later 

creation or modification of the artefact. A well-known example is Prussian 

blue, a pigment that was invented in 1704 by Diesbach in Berlin [4,5]. 

A positive identification of this material enables dating post quem. On the 

other hand, certain pigments fell into disuse, as they were substituted by 

better pigments or by pigments that were less harmful or less expensive. 

Finding such pigments makes it possible to date an object of art ante quem. 

Natural Indian yellow is such a pigment that disappeared from the palette 

around 1900. This pigment was obtained from urine of cows that were fed 

with mango leaves. Although a good pigment was obtained, this practice 

harmed the animals, as the salts formed needle-shaped crystals in their 

kidneys. Therefore, under pressure of animal welfare activists, this practice 

was forbidden by law and thus, the identification of natural Indian yellow in 

an object of art indicates that the work almost certainly dates from before 

that period [6]. 

Anachronistic use of materials is a strong indication for an artefact to 

be a fake. In making these conclusions, care has to be taken that no 

restorations are analysed. Another way to recognize forgeries by spectroscopic 

means is by comparing the pigments in a specific object of art with 

those in a large set of other artefacts by the same artist. By analysing an 

extended collection of his paintings, the artist's palette can be reconstructed 

as a function of time. The discovery of apparent contradictions 

can be indicative of a fake. 

Another important reason for art analysis is to obtain answers to specific 

questions of conservators, curators or (art-)historians. Such questions 

include the determination of the origin of degradation. An example was 

the identification of copper in a green pigment in a mediaeval manuscript of 

the Ghent University Library [7]. This pigment caused the deterioration of 

the manuscript as the parchment that served as substrate was corroded. 

For each examination of artefacts, the information obtained and the risk 

of possible damage should be balanced. The art investigator should aim to 

obtain as much information as possible on the artwork, while damaging it as 

little as possible (and if possible not damaging it at all). Therefore, it is a good 

idea to apply several non- or micro-destructive methods, in order to obtain 

complementary information [3,8,9]. In our case, two sensitive microanalytical 

techniques, namely Total-reflection X-Ray Fluorescence analysis 

(TXRF) and Micro-Raman Spectroscopy (MRS) were used, in combination 

with a gentle micro-sampling method [10-12]. 

637


TXRF [13,14] reveals the elemental composition of the sample. As only 

the elements with Z > 14 are detected, the analysis is limited to the 

inorganic pigments. Most of the pigments can be identified by means of their 

"key elements." For example, the presence of mercury in a red sample 

indicates the presence of vermilion. Despite this, in some cases TXRF is not 

able to identify the pigments unambiguously. The presence of copper in a 

green sample might indicate the presence of copper resinate, malachite, 

verdigris, posnjakite, brochantite, another green copper pigment or even the 

blue pigment azurite, mixed with a yellow pigment. On the other hand, 

TXRF determines the relative amounts of the detected elements, and thus 

the relative amounts of the pigments in the sample can be identified. 

Moreover, TXRF provides an idea of the (elemental) impurities in the sample. 

MRS provides complementary information on the sample. Whereas TXRF 

is not able to distinguish between several pigments with the same key 

element, a molecular technique such as MRS provides information on the 

chemical environment of these elements and (if any) on their crystalline 

structure [15-17]. Moreover, MRS is not restricted to inorganic materials, 

but it is possible to record spectra of organic dyes and binding media as well. 

By using microscope optics, it is possible to record spectra from samples with 

a diameter of ca. 1 m and thus all the pigment grains can be identified 

individually. Despite these advantages, by focussing on different pigment 

grains, the technique cannot be used for quantitative analysis of this type of 

sample. If no useful Raman spectrum can be recorded because of fluorescence 

effect giving rise to an excessive spectral background, a laser with another 

wavelength can be chosen, if available. 

In some cases, Raman spectroscopy may be applied in a direct way 

[18-20]. This approach has the advantage that no sampling is required. 

Several groups have positioned loose leaves or whole bound manuscripts 

under the Raman microscope [21,22]. By changing the position of the 

manuscript or the folio, it was possible to analyse different painted areas. 

During these investigations, care has to be taken not to damage the fragile 

artefact, either manipulating it or by applying too much laser power. With 

standard Raman microscopes, unless small manuscripts are examined, it is 

often impossible to reach the central parts of the manuscript, because of 

spatial limitations. In this case, an alternative is the use of a tilted 

microscope [19] or a mobile probe equipped with fibre-optics [20]. 

As two complementary analytical methods are involved [23], it may be 

helpful to make use of a convenient sampling method. In art analysis it is 

critical to damage the object as little as possible, especially when delicate 

manuscripts are involved. For TXRF investigations, it is necessary that the 

638


sample can be spread out homogeneously, as a fine (mono-) layer of grains, 

over a flat sample carrier. For these reasons, a gentle micro-sampling method 

was developed [10-12,24]. This procedure consists of gently rubbing a cotton 

bud over the painted surface, thus transferring a small amount of paint 

(ca. < 1 ug) from the artefact to the Q-tip. This sampling method does not 

leave any visible trace on the artefact. In order to avoid loss of material and to 

eliminate contamination of the sample, the cotton bud was mounted in a 

plastic sample container. In the laboratory, the Q-tip is tapped on to a 

suitable sample carrier. An important disadvantage of this method is that 

the information is limited to the surface layer. By using this sampling 

procedure it is not possible to examine a paint layer that is covered with 

varnish. For the examination of illuminated manuscripts, this is barely a 

drawback, but for the analysis of easel paintings sampling has to be done 

when the varnish is removed, e.g., when the painting is being restored. 

This Q-tip sampling method has been applied for the present study. 

14.2.1 Analysis of manuscripts 

The spectroscopic examination of mediaeval manuscripts focuses on the 

different materials in these objects of art: paint (consisting of pigment and 

binding medium), parchment, dyes and ink. 

14.2.1.1 Inorganic pigments 

One of the most striking aspects when admiring mediaeval illuminated 

manuscripts is the brightness of the painted colours. Paint consists of 

a mixture of a binding medium and a colouring agent. If the colouring 

agent is insoluble in the medium, it is called a "pigment"; otherwise the term 

"dye" is used. See Table 4.6 for an overview of inorganic pigments. 

Red pigments 

During the middle ages, red was an important colour, and was the colour 

most often used for capital letters, paragraph marks, running titles, etc. In 

that period several red and orange pigments were in use. XRF key elements 

of the most important red pigments are tabulated in Table 14.1; the 

corresponding Raman spectra are shown in Fig. 14.1. Vermilion (HgS) is a 

pigment that was known already to the Romans. They called it "minium," a 

name that caused confusion in later periods, as this term was also used 

for red lead (Pb 3O 4) [25]. The high intensity Raman band at 254 cm -1 , in 

the spectrum of vermilion, can be assigned to the v(Hg-S) stretching 

vibration [25]. Different lead oxide pigments, such as red lead and massicot 

639

TABLE 14.1 


Overview of some important red pigments, their chemical composition, TXRF key 

elements and Raman band positions 

Pigment Other names 

Vermilion Cinnabar, minium HgS 

Red lead Minium 

Hematite Main component 

of red ochre 

Chemical TXRF key Raman wavenumbers 

composition elements (cm - 1 ) 

Pb 3 0 4 

Fe 203 

Hg 343(m), 283(w), 254(vs), 

144(vw), 112(vw) 

Pb 549(s), 477(vw), 457(vw), 

391(m), 314(w), 231(w), 

224(w), 152(m), 122(vs) 

Fe 659(vw), 613(w), 499(w), 

412(m), 394(vs), 246(w), 

227(vs) 

Indications of relative peak intensities are provided (vs, very strong; s, strong; m, medium 

intensity; w, weak; vw, very weak; sh, shoulder). 

(see section 'Yellow Pigments") can be distinguished by their Raman spectra, 

as both the crystal symmetry and the oxidation state of Pb are different. 

The intense Raman band at 547 cm 1 wavenumber shift can be assigned to 

the v(Pb-O) stretch vibration, while the band at 224 cm-l is related to the 

b(O-Pb-O) deformation. Hematite is the main component of different forms 

of red ochre, i.e., earth pigments that have been in use since prehistory. 

Using Raman spectroscopy their presence was demonstrated in prehistoric 

rock art in the southwest of France [26]. Raman and FT-IR spectra of 

different types of ochres were recorded by Bikiaris et al. [27]. 

c 

vZ 

1: 

600 500 400 300 200 

Raman Wavenumbers /cm -1 

Fig. 14.1. Raman spectra of red inorganic pigments: (a) vermilion, (b) red lead and 

(c) hematite (baseline-corrected). Raman spectra were recorded with a Renishaw 

System-1000 spectrometer with a laser of 780 nm. 

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a 

700 

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. . . . . . . . . . . . . . . . I l I l l l 

100


Blue pigments 

In the middle ages, two important blue mineral pigments were available, 

viz. azurite (2CuCO 3-Cu(OH) 2) and lapis lazuli (natural ultramarine, 

Nas... oA1 0 6Si 06 24S 2... 4) [4,5,28]. Azurite is a basic copper carbonate, 

that is found as a mineral together with the green pigment malachite 

(CuCO 3.Cu(OH) 2). In Western Europe, it was the most important blue 

pigment until the middle of the 17th century. The natural form of 

ultramarine is lapis lazuli, a semiprecious stone that prior to this period 

(?) was only found in Badakshan (in present Afghanistan). Purification of the 

milled material was more complex and time-consuming than for most 

minerals and this, combined with its rareness and the long distance it had to 

travel, made it the most expensive mediaeval pigment. Only around 1830, 

three scientists (J.B. Guimet, C. Gmelin and F.A. Kottig) independently 

succeeded in synthesizing ultramarine [5]. Lapis lazuli and synthetic 

ultramarine are chemically identical and they may only be distinguished 

from each other by the presence of impurities. Smalt (CoO nSiO2) is the 

earliest cobalt pigment. It is suspected to originate from glass production. 

According to Schramm and Hering [4] it was in use from the 15th century 

onwards in Western Europe. Raman spectra of some blue pigments are 

shown in Fig. 14.2 and are tabulated, along with TXRF key elements in 

Table 14.2. As azurite is anisotropic, the spectrum is strongly orientationdependent. 

The intense band at 1096 cm-1 derives from the symmetrical 

b 

Dc 

n 

ZJ U) Co 

(D 

1600150014001300120011001000 900 800 700 600 500 400 300 200 100 

Raman Wavenumbers/cm -1 

Fig. 14.2. Baseline-corrected Raman spectra of blue inorganic pigments: (a) azurite, (b) 

lapis lazuli and (c) smalt. Spectra recorded under similar conditions as for Fig. 14.1. 

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stretch vibration of the carbonate ion. At lower wave numbers different 

Cu-O lattice vibrations are found. The Raman spectrum of ultramarine is 

characterized by the very strong band at 545 cm-l, which is assigned to the 

v([S-S]-) stretch vibration [29,30]. The other bands in this spectrum are 

weak to very weak. The Raman spectrum of a smalt sample shows three 

medium to strong Raman bands (at 692, 460 and 197 cm 1). Lapis lazuli has 

no TXRF key elements, as the characteristic X-rays of low-Z elements are 

absorbed by the air and by the Be-window of the detector. Additionally, the 

sulphur-K lines overlap with Pb-M(x radiation. Moreover, as sulphur is 

present in several traditional binding media, this element is not a conclusive 

indicator for the presence of lapis lazuli. 

Yellow pigments 

Lead-tin yellow, type I (Pb 2SnO 4) was in use between ca. 1300 and ca. 1750 

AD. The pigment lead-tin yellow, type II (PbSn 2SiO 7) was a pigment that 

probably originated from Venetian or Bohemian glass production. It became 

available at the beginning of the 14th century [31] . Massicot (PbO) is a yellow 

lead(II)oxide. Yellow ochre (Fe 203nH 20)) is an important earth pigment that 

was in use since prehistory. The main component is limonite. Raman spectra 

are shown in Fig. 14.3 and are summarized together with the TXRF key 

elements in Table 14.3. In the spectrum of massicot the very strong band at 

143 cm 1 can be assigned to the v(Pb-O) stretching vibration [30]. In the 

same region (130 cm l) in the spectrum of lead-tin yellow (type I) a very 

C 

c 

a 

1000 900 800 700 600 500 400 300 200 100 


Fig. 14.3. Raman spectra of yellow inorganic pigments: (a) lead-tin yellow (type I), 

(b) massicot and (c) limonite (baseline-corrected). Spectra recorded under similar 

conditions as for Fig. 14.1. 

643

TABLE 14.3 


Overview of some important yellow pigments, their chemical composition, TXRF key 


Pigment Other names Chemical TXRF key Raman wavenumbers 

composition elements (cml) 

Lead-tin Pb 2 SnO 4 Pb, Sn 613(vw), 525(vw), 456(w), 

yellow 379(vw), 336(vw), 292(w), 

(type I) 273(w), 196(m), 130(vs) 

Massicot PbO Pb 384(vw), 289(m), 217(vw), 

143(vs), 124(vw) 

Limonite Main component Fe 203-nH 2O Fe 552(w), 484(w), 420(w), 

of yellow 400(m), 389(s), 302(m), 

ochre 247(w), 206(vw) 



intense Raman band is found. The Raman spectrum of red ochre is easily 

distinguished from the spectrum of yellow ochre, since many peak positions 

and intensities are changed. 

Green pigments 

Many different green pigments have been used by artists. Copper pigments 

in particular were commonly used in the middle ages. In the literature often 

verdigris (Cu(CH 3COO) 2 nCu(OH) 2) or malachite (CuCO 3-Cu(OH) 2) are 

cited [4], but in reality many more green copper pigments were in use 

[32,33], several of these being of mineral origin. Common examples are the 

basic copper sulphates, such as posnjakite (Cu 4SO 4(OH)6-H 20) and 

brochantite (Cu 4SO 4 (OH) 6). In the middle ages, verdigris was synthesized 

by the reaction of vinegar with copper plates and, depending on the recipe, 

different shades and types of verdigris were obtained. Malachite, on the 

other hand, was a natural mineral. Copper resinate results from the 

dissolution of copper salts in turpentine and resinous material. Chrysocolla 

is a green copper silicate of mineral origin that, after grinding, was used as a 

pigment, while the main component of green earth is an iron silicate. 

When performing dispersive Raman spectroscopy with a near infrared 

laser (X = 780 nm), green pigments in general give rise to rather weak 

Raman spectra with low signal-to-noise ratios, as a result of the absorption of 

the laser light (Fig. 14.4, Table 14.4). 

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1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 

Raman Wavenumbers/cm-1 

Fig. 14.5. Raman spectra of black pigments: (a) carbon black and (b) iron black. 

Spectra recorded under similar conditions as for Fig. 14.1. 

as preparation layer, mixed with animal glue, while in Italy gypsum 

(CaSO42H 2 0) was more commonly used for the preparation layer, using a 

technique called "gesso." For the white pigment, anhydrite (CaSO 4) was 

frequently applied, a natural mineral that is found together with gypsum, 

but that often was synthesized by calcination of gypsum. One of the most 

important white pigments is white lead (2PbCO 3-Pb(OH) 2); beside its 

colouring properties this material is appreciated as a siccative. Permanent 

white (BaSO 4) is a synthetic white pigment that has been available since the 

beginning of the 19th century [5]. The natural form, which is called barite, 

can occasionally be observed in mediaeval manuscripts, often together with 

gypsum [35]. Normally it is not used as white pigment as it lacks masking 

power. The Raman spectra of different white materials are easily distinguished 

(Fig. 14.6). These spectra all have a very intense Raman band, which 

TABLE 14.5 

Overview of some important black pigments, their chemical composition, TXRF key 


Pigment Other names Chemical TXRF key Raman 

composition elements wavenumbers (cm 1 ) 

Carbon black Lamp black C - 1594(m), 1297(s) 

Iron black FeOFe 20 3 Fe 667(m), 529(w), 

492(w), 306(m) 



647

D 

a' tO 

2 

L 

TABLE 14.6 


Overview of some important white pigments, their chemical composition, TXRF key 


Pigment Other Chemical TXRF key Raman wavenumbers (cm l) 

names composition elements 

Chalk CaCO 3 Ca 1086(vs), 712(m), 282(m), 

156(m) 

Gypsum CaSO42H20O Ca 1372(vw), 1134(w), 1006(vs), 

669(w), 618(w), 492(m), 

413(m), 317(w), 210(w), 

181(w),122(w) 

White lead 2PbCO 3 Pb(OH) 2 Pb 1056(vs), 418(w), 353(vw), 

260(m), 203(m), 154(m) 

Permanent Barite BaSO 4 Ba 1165(vw), 1137(vw), 986(vs), 

white 645(w), 615(w), 460(m), 

451(m), 188(vw), 153(vw) 



together or unmixed) and several animal glues have frequently been 

applied. Casein, a phosphoprotein, can easily be obtained from milk, as it 

precipitates after acidification and heating of skimmed milk. Albumen has 

been applied in different ways: glair has been used as such and the protein 

can be mixed with a small amount of water to adjust the viscosity. Albumen 

has even been applied together with egg yolk, the latter component acting 

as emulsifier. At the time animal glues (i.e., gelatin, bone glue, skin glue, 

fish glue, isinglass, etc.) were not often used in manuscripts as binding 

media in paint, but applied as fixative (e.g., to glue gold leaves). Raman 

spectra of proteins are characterized by the presence of intense amide I 

(ca. 1650 cm-l) and amide III bands (ca. 1250 cm-l 1 ). Often, a sharp Raman 

band is observed at ca. 1002 cm - l , which is assigned to the aromatic ring 

breathing vibration of the phenylalanine amino acid. 

Another group of binding media that was often used in mediaeval 

manuscript production is of vegetal origin. Starch (poly-D-glucose) has 

been used as glue or substrate for organic dyes. Its Raman spectrum is 

dominated by an intense band at 477 cm-l,which can be attributed to a 

deformation of the backbone of the polysaccharide chain. Unlike resins, 

gums are polysaccharide plant exudates that are soluble or swell in water 

(gel formation). Among these, gum Arabic is the most important. Being 

harvested from different acacia species, this polysaccharide consists of 

649


different monosaccharides, among which L-arabinose and D-galactose. The 

Raman spectra of gums are composed of broad, overlapping bands, that 

can be assigned to (C-H) bending vibrations and v(C-O) and v(C-C) 

stretching vibrations, all below 1500 cm 1. Raman spectra of some 

binding media are shown in Fig. 14.7. 

14.2.1.3 Iron gall ink 

Iron gall ink is one of the most frequently used mediaeval inks, besides 

charcoal [39]. Iron gall ink is prepared by adding vitriol (iron(II)sulphate, 

FeSO 4) to the aqueous extract of, among others, gallnuts. In its pure form, 

the ink is the precipitated complex of the iron ion with four molecules of gallic 

acid, but in practice the extract also contains several esters such as di-gallic 

acid and tannin besides the pure gallic acid. As the ink is applied on the 

paper or parchment, one observes the darkening of the ink, a phenomenon 

that has been ascribed to the oxidation of Fe 2 + to Fe 3 + under the influence of 

oxygen in the air [40]. By performing TXRF analysis on mediaeval iron gall 

ink samples, large amounts of Fe are observed, often accompanied with 

smaller amounts of Cu and Zn. These may be ascribed as impurities in either 

the iron ore that was used for the production of vitriol or in the vessels that 

were used for the production or storage. Another possible explanation is the 

use of several admixtures in the vitriol that was used. 

n 

E 

. 

S: 

1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 

Raman Wavenumbers/cm 1 

Fig. 14.7. Baseline-corrected Raman spectra of a proteinaceous binding medium: 

albumen (a) and two polysaccharide media: starch (b) and gum Arabic (c). Spectra 

recorded under similar conditions as for Fig. 14.1. 

650


In Fig. 14.8 Raman spectra of pure gallic acid, FeSO 4, mediaeval iron 

gall ink and a laboratory analogue are presented. The laboratory sample 

has been synthesized by using pure FeSO 4 and gallic acid powder, dissolved 

in de-mineralized water. It is readily observed that the spectrum of 

mediaeval ink is much more complex than that of the modern product; other 

compounds in the gallnut extract may form complexes as well and the 

crystallinity of the precipitate may be different. The Raman spectrum of 

gallic acid powder consists of several well-defined Raman bands. The 

doublet at ca. 1600 cm - 1 may be attributed to the v(C=O) stretching 

vibration and the benzene quadrant stretch vibration. The intense band at 

961 cm -1 may be attributed to the benzene ring breathing vibration, while 

the numerous and overlapping bands between 1550 and 1000 cm - 1 are 

correlated with (C-H) deformations and v(C-O) and v(C-C) stretching 

vibrations. The spectrum of FeSO 4-x H 20 is dominated by the Raman band 

that can be assigned to the (S0 4 ) symmetric stretch vibration of the 

sulphate group (976 cm 1 ). 

0M 

Q) 

C: 

I: 

1800 1600 1400 1200 1000 800 600 400 200 

- 1 

Raman Wavenumbers/cm 

Fig. 14.8. Baseline-corrected Raman spectra of (a) gallic acid, (b) FeSO 4, (c) mediaeval 

gall ink and (d) a laboratory specimen. Experimental conditions for the preparation of 

the laboratory sample are given in the text. Spectra recorded under similar conditions 

as for Fig. 14.1. 

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14.2.1.4 Parchment 

Parchment was an important writing medium during the middle ages, 

although in the early middle ages papyrus was used as well, and from the 

13th century onwards paper, already known for centuries in China and the 

Arab world, was introduced. Mediaeval paper was made from linen rags [1]. 

In mediaeval times, the percamentarius or parchmenter had the task of 

transforming animal skins into parchment. The first stage of this delicate 

process consisted of the selection of good skins from healthy animals. After 

skinning, the pelt had to be washed under cold running water. Often they 

were put into a vessel with lime for several days to promote a partial 

decomposition of the skin. As the skin started to rot, the hairs were loosened 

from it. In the next stage, the wet skins were taken out of the lime and the 

remaining hairs were scraped off with a curved knife with two handles. Then 

the remaining flesh and fat were scraped from the reversed side of the skin. 

In this phase care had to be taken not to cut the skin by accident. The wet 

skin was then stretched on a frame, where it was allowed to dry. While 

drying, the parchment tended to shrink. The dried and stretched material 

was then scraped again for several times in order to make it whiter and 

thinner. The pieces of skin that were removed could be boiled to produce 

animal glue. Often the parchment was treated with chalk to make it look 

paler and to prepare it for the writing process. Parchment was very 

expensive and therefore in several mediaeval manuscripts repairs can be 

found: little holes were sometimes sewn to prevent further damage. 

Parchment is a proteinaceous material, so its Raman spectrum (Fig. 14.9) 

contains well-defined amide I and III bands, similar to the spectra of 

proteinaceous binders. As the parchment is treated with chalk, the intense 

Raman band at 1086 cm - 1 (v(CO3) symmetrical stretch) is also observed. 

14.2.2 Sources of impurities 

When working with micro-samples, special care has to be taken to avoid any 

contamination, which may lead to false conclusions. One should always be 

careful to take a sample that is representative of the work or paint area 

under study. Sampling, sample transportation to the laboratory and 

preparation by the analyst should be done in such a way that contamination 

is avoided. But even when all these conditions are fulfilled, the nature of 

mediaeval manuscripts makes two forms of contamination hard to avoid; 

these types have been dubbed "internal" and "external" contamination [35]. 

Internal contamination originates from imprecise sampling: e.g., during the 

analysis of minute details in initials or border illuminations in mediaeval 

652

DZ 


and the mineral impurities contribute to the final impurity pattern. 

Moreover, during grinding more impurities could be introduced. Other 

pigments were synthesized from mineral sources; here again, during 

synthesis traces of impurities may be added. During transport and trade 

in pigments still more impurities could be introduced accidentally or 

intentionally (in the case of adulteration). Finally, in the workshop the 

pigments were ground and blended, in order to obtain the right hue. By 

mixing the pigments with binder, paint was made. At all these stages 

involved in pigment and paint production elemental impurities were 

introduced, resulting in the intrinsic impurity pattern of the paint layer, 

which is a reflection of the whole transformation that the pigment underwent 

from the mineral ore to the miniature. During this processing many different 

influences affect the impurity pattern, resulting in a combination of trace 

elements that is unique for a specific batch of paint. Thus, by analysing the 

elemental composition, it is possible to discriminate between different 

batches of paint, and thus between the workshops or miniaturists [28,41,42]. 

14.3 ANALYSIS OF THE MANUSCRIPTS FROM THE COLLECTION OF 

RAPHAEL DE MERCATELLIS 

14.3.1 Introduction 

Raphael de Mercatellis (1437-1508) [43] was a natural son of Philip the 

Good, Duke of Burgundy, born in Bruges, in a Venetian family of merchants, 

the Mercatelli family. He studied theology at Paris University and became a 

monk in the Benedictine abbey of Saint Peter in Ghent. Later, he became 

abbot of the abbey of Saint Peter in Oudenburg, where the onset for his 

library was given. During his ecclesiastical career he also became abbot of 

the abbey of Saint Bavon in Ghent, suffragan of Tournai and nominal bishop 

of Rhosus. 

Whereas contemporary bibliophiles preferred literary, moralistic or 

historical texts written in French, Mercatellis' library contained works 

written in Latin, covering a wide range of subjects. Together with works on 

theology and ecclesiastical law, his collection also contained works by 

classical authors (such as Aristotle and Plutarch) and manuscripts on 

astronomy, medicine and mathematics. Although book printing was invented 

during his lifetime (Gutenberg bible, ca. 1456), the books he commissioned 

were manuscripts. Moreover, there is a manuscript that is known to be 

copied from a printed version (Georgus Reish, Margarita Philosophica, 

654


Ghent University Library Ms. 7). The manuscripts were written on 

parchment and they have remarkably large dimensions. Often Mercatellis' 

coat of arms or his monogram is found. Some manuscripts are illuminated 

with acanthus borders, historiated initials or miniatures. 

As no contemporary catalogue of his library survives, the extent of his 

collection at that time is unknown. The remaining lists, dating well after his 

death, mention 80 manuscripts; today, 60 of these are spread out over 

different libraries. The manuscripts have been studied on codicological [43] 

and stylistic grounds [44] and different groups of works can be distinguished, 

which can be related to different periods in Mercatellis' life and to different 

workshops. 

It is very likely that the Mercatellis manuscripts were manufactured in 

private workshops, but little is known on the organization and way of 

working in these workshops. There is a suggestion that the provenance of the 

manuscripts is located near Ghent or Bruges. The latest art historical 

research tends to suggest a Bruges provenance, as there appears to be 

a relationship between the miniatures in the Ghent University 

Library Manuscripts 2 and 5 (both astrological treatises) and the Vrelant 

workshop [45]. 

The aim of this work is to illustrate how the spectroscopic examination of 

mediaeval manuscripts from the Mercatellis collection can provide information 

on the way the manuscripts were produced. Information will be 

gained on the relationships between samples from within a manuscript 

(intra-manuscript relationship). The spectroscopic examination of intermanuscript 

relationships has been examined elsewhere [35,46]. In what 

follows, we focus on the paint composition of border illuminations, initials 

and paragraph markings. 

14.3.2 Pigment identification with TXRF and MRS 

The pigments in the manuscripts were examined by means of MRS and 

TXRF analysis. All the samples in the manuscript contain a significant 

amount of Ca. This could originate from the treatment of parchment with 

chalk, in order to prepare it for writing. From Raman investigations, it 

turned out that this element was present in the form of calcium carbonate, as 

well as gypsum. Another white component that was detected in these 

manuscripts is barite (BaSO 4). The synthetic form of this mineral was used 

as a white pigment since the beginning of the 19th century, namely 

permanent white [5]. As these manuscripts are mediaeval, and taking into 

655


account that no signs of later overpaintings or restorations were found, it is 

likely that we found the natural form of this pigment, probably present as an 

impurity in gypsum. 

From the TXRF investigations it turned out that the blue samples 

contained an important amount of Cu, key element for azurite. These 

findings were confirmed by the Raman investigations. No lapis lazuli was 

found in the Mercatellis manuscripts. All the red samples contain vermilion. 

Some red samples feature an admixture of red lead. 

Figure 14.10 shows a Raman spectrum from the green pigment out of 

De viris clarissimis by Plutarch (Ghent University Library, Ms. 109). The 

quality of the Raman spectrum of many green pigments is relatively poor 

(low SIN ratio), as the 785 nm laser light is absorbed by the green pigment, 

and as the sample produces fluorescence in this region. Despite this, it was 

possible to identify the pigment. The spectrum is identical to the spectrum of 

a basic copper sulphate that was synthesized under laboratory conditions 

[47]. X-ray diffraction of this synthetic pigment showed that the material had 

the same composition as the natural mineral brochantite. 

FU 

.2 

Cr 

C: 

1100 1000 900 800 700 600 500 400 300 


Fig. 14.10. Raman spectrum of a green pigment from De iris clarissimis by Plutarch 

(Ghent University Library, Ms. 109). Spectrum recorded under similar conditions 

as for Fig. 14.1. 

656


14.3.3 Intra-manuscript comparison of Expositio problematum 

Aristotelis 

Spectroscopic methods can help art historians to discriminate between 

different workshops. In the Mercatellis manuscript Expositio problematum 

Aristotelis (Ghent University Library, Ms. 72), the acanthus borders may be 

divided into three distinct groups (Fol. lr-151v, 152r-233v and 234r-395v) on 

stylistic grounds. The difference between the first two groups is minimal and 

therefore these groups were previously considered as a single class. For this 

research, 123 micro-samples were taken from blue leaves in acanthus 

borders and blue initials. In Fig. 14.11 the relative amounts (by TXRF) of Ca, 

Pb, Fe, Zn and As are presented. These elements are all impurities in the 

blue paint, where the blue Cu-containing pigment azurite is present. 

From this representation, the Fe:Zn ratio appears to be mainly 

responsible for the differentiation between the first and second parts of the 

manuscript (U + A) on the one hand, and the last part (0) on the other hand. 

The same groups are found for the blue samples from the initials. The 

discrimination between the first () and second (A) group becomes clear if 

Fe Borders Fe 

As Zn Pi Ca 

As Zn Pb Ca 

Fig. 14.11. TXRF analysis of 123 blue micro-samples, taken from the borders 

and initials in the Mercatellis manuscript Expositio problematum Aristotelis 

(Ghent University Library, Ms. 72). Legend: · fol. lr-144v; A fol. 153r-230v and 

0 fol. 234r-395v. Group marks are purely indicative. 

657


the relative amounts of Fe:Ca:Pb are considered. When considering the 

samples from the initials, the relative amount of Pb for the first part of the 

manuscript () is clearly lower than for the second part (A). A similar 

discrimination is found when considering the Fe:Ca ratio in the blue samples 

from the acanthus borders. 

These results illustrate the possibilities of spectroscopic examination to 

assist in art historical research. During a primary stylistic examination, two 

distinct groups were found, but after conscientious evaluation of the TXRF 

results, this thesis had to be adjusted, as three groups were distinct. The 

need for close interdisciplinary consultation during this research is shown as 

well with this example. 

14.3.4 Analysis of Decretum Gratiani 

Decretum Gratiani (Ghent, University Library Ms. 3) is a medley of texts on 

canon law, collected by the Bolognese monk Gratianus. The manuscript is 

divided into three volumes (labelled 3-I, 3-II-1 and 3-II-2). At the end of 

volume 3-II-1 a colophon states that Raphael de Mercatellis acquired this 

book/volume in 1505: 

Revendus pater Raphael episcopus Rosensis, abbas Sancti Bavonis, comparavit 

hoc volumen anno XVV 

As this manuscript is divided into several volumes, one might wonder 

whether the manuscript was produced by several workshops. This was 

examined by analysing the impurity patterns in a very large number (128) of 

samples from the different volumes in the manuscript. In Fig. 14.12 the 

K Ca Hq 

Fig. 14.12. TXRF analysis of 128 micro-samples, taken from blue initials in three 

volumes of Decretum Gratiani (Ghent University Library, Mss. 3-I, 3-II-1 and 3-11-2). 

Legend: Ms. 3-I; 0 Ms. 3-II-1 and · Ms. 3-1-2. 

658


ratios of the elemental composition of Fe:Ca:K and Fe:Zn:Hg is given for the 

blue initials over the manuscript. From these diagrams, it is seen that the 

classes overlap; the centroids for each class are almost coincident. Therefore, 

we should conclude that it is impossible to discriminate between the different 

volumes, based on their TXRF impurity pattern. Other elements gave 

similar results. These findings show that there is great similarity between 

the volumes and they support the thesis that only one workshop has been 

involved in the production of this manuscript. 

Such homogeneity is also confirmed by the analysis of ink samples. 

Fourteen samples throughout the different volumes of the manuscript have 

been analysed. Samples originated from the main text, from annotations as 

well as from corrections. All the samples contained iron and zinc, key 

elements for iron gall ink [48]. The presence of metallogallic ink was also 

confirmed by Raman spectroscopy. Comparison of the elemental composition 

of the ink samples may also give some indication on the way the manuscript 

was produced and of the allocation of tasks in the workshop. Italian 

researchers have determined the elemental composition of the ink in the 

notes of Gallileo Gallilei. By comparing the elemental composition of the ink 

in his undated letters with the composition of the ink in his diary, they aimed 

to order these writings [49]. By comparing the elemental composition of the 

ink samples in Decretum Gratiani, it was found that all the samples had a 

similar composition, which supports the theory that the whole manuscript 

was produced in a single workshop. Only the composition of the sample from 

the colophon was different from the others, but it is very likely that this 

difference is sooner due to a different preparation of the parchment of the 

last page than a real different composition of the ink: when omitting the 

difference in Ca content the sample has a composition similar to that of 

the others [50]. 

14.4 CONCLUSION 

In this work it was shown how a combined approach of MRS and TXRF 

analysis can be of interest for the examination of mediaeval manuscripts. 

Both methods can be applied in an almost non-destructive way by using a 

gentle micro-sampling method. By using TXRF, the inorganic pigments are 

identified by using their key elements. Raman spectroscopy provides 

information on the molecular composition, inorganic as well as organic, of 

the different grains in the sample. 

In addition to identification of pigments, it is possible by using TXRF to 

obtain an overview of the impurity pattern in the sample. This impurity 

659


pattern is a reflection of all the stages in the pigment production, from 

the mineral source to the paint production in the workshop. Therefore, the 

analysis of the impurity patterns may be of use for the study of the 

provenance and the organization of the workshops where the manuscripts 

were produced. This approach has been applied for the investigation of two 

manuscripts from the former library of Raphael de Mercatellis. It was shown 

how the study of the elemental impurities can be of use for discriminating 

different hands in a manuscript or to indicate the same provenance of 

different volumes of a single manuscript. 

Acknowledgements 

The authors wish to thank Martine De Reu, Reinhold Klockenkimper, Guido 

Van Hooydonk and Alex von Bohlen for their cooperation in this research. 

Mark Clarke is acknowledged for proofreading this text. This research has 

been supported by the fund for scientific research-Flanders (FWO- 

Vlaanderen) and by the Ghent University (Bijzonder onderzoeksfonds- 

BOF). PV is especially grateful to the Fund of Scientific Research-Flanders 

(FWO-Vlaanderen) for his postdoctoral fellowship. 

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