# The Mappa mundi of Albi: Insight into the manufacturing, life and conservation state of an 8th century world map

Laurianne Robinet, Sylvie Heu-Thao, Giulia Galante, Gaël Latour, Aurélie Tournié, Céline Daher, Anca Dan, Marie-Claire Schanne-Klein, Anne Michelin, Jocelyne Deschaux

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## To cite this version:

Laurianne Robinet, Sylvie Heu-Thao, Giulia Galante, Gaël Latour, Aurélie Tournié, et al.. The Mappa mundi of Albi: Insight into the manufacturing, life and conservation state of an 8th century world map. Journal of Cultural Heritage, 2025, 74, pp.341-352. 10.1016/j.culher.2025.05.013. hal-05185402

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Submitted on 24 Jul 2025

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Original article

# The *Mappa mundi* of Albi: Insight into the manufacturing, life and conservation state of an 8th century world map

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Laurianne Robinet<sup>a,*</sup>, Sylvie Heu-Thao<sup>a</sup>, Giulia Galante<sup>a,b</sup>, Gaël Latour<sup>b,c</sup>, Aurélie Tournié<sup>a</sup>, Céline Daher<sup>a</sup>, Anca Dan<sup>d</sup>, Marie-Claire Schanne-Klein<sup>b</sup>, Anne Michelin<sup>a</sup>, Jocelyne Deschaux<sup>e</sup>

## ARTICLE INFO

**Article history:**

Received 20 February 2025

Accepted 23 May 2025

**Keywords:**

Illuminated parchment

World map

Physicochemical analyses

Medieval manuscript

Imaging technique

## ABSTRACT

The *Mappa mundi* of Albi is one of the oldest examples of spatial representation of the Western world. The small map conserved on the verso of folio 57 in manuscript 29 of the *Médiathèque Pierre Amalric* in Albi (France) was drawn on parchment, probably made in the second half of the 8th century, somewhere between south-western France and northern Spain, maybe in Albi itself. Because of its exceptional importance for the history of space representation, the map, together with the *Index of seas and winds* facing it, on the recto of folio 58, was recorded in the UNESCO Memory of the World Register in 2015. The detailed study published here has examined the manuscript's structure and characterised the different constitutive materials. Observations and physicochemical analyses were performed on the map and the index, from the micro to the macroscale, combining optical microscopy, XRF, FORS, FTIR, and micro-Raman spectroscopy, hyperspectral imaging, proteomic analysis, and non-linear optical microscopy. Three manuscripts conserved at the same library or suspected to have been produced in the scriptorium of Albi have also been examined for comparisons. This material investigation complements the historical studies of the map by shedding new light on the manufacturing, life, and conservation state of this exceptional document.

© 2025 The Authors. Published by Elsevier Masson SAS. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

## 1. Introduction

The *Mappa mundi* of Albi (France), preserved in the Albi Ms. 29 fol. 57v, is one of the two oldest West-European representations of the inhabited world; it can be seen online at https://cecilia.mediatheques.grand-albigeois.fr/idurl/1/97 (pages 119–120 of the digitalized file https://cecilia.mediatheques.grand-albigeois.fr/viewer/97/?offset=#page=119&viewer=picture&o=&n=0&q=; full bibliography at https://data.biblissima.fr/entity/Q227529). The other map covers the folios 63v-64r of the manuscript *Vaticanus Latinus* 6018, a small codex (208 × 144 mm), written mostly in the first half of the 9th century. The Vatican codex can be seen online at https://digi.vatlib.it/view/MSS_Vat.lat.6018/0131, with full bibliography at https://portail.biblissima.fr/ark:/43093/

mdata80df2ed2387f91e45dfd6721c2c38ba4e8b8ce2d. The Albi map was drawn on parchment, most probably made during the second half of the 8th century, between south-western France and northern Spain - either in the region called *Septimania* or in Albi itself [1]. The *Mappa mundi* of Albi and the *Index of seas and winds* which faces it (on fol. 58r) are included in a 77 folios manuscript (27 × 22.7 cm) belonging to the *Médiathèque Pierre Amalric* in Albi, France, and recorded in the UNESCO Memory of the World Register in 2015.

The manuscript 29 is an early Medieval schoolbook, now composed of 26 Latin texts about grammar and rhetoric, moral philosophy, history, geography, and theology. Several scribes wrote this parchment codex mostly between the 8th and 9th centuries. The manuscript also contains texts dated to the 10th and the 12th centuries, which testify to its continuous use and transformation during the Middle Ages. The manuscript remained in the Albi cathedral library until the French Revolution, when it was seized. This saved it from the fire that affected the cathedral's archives in 1794.

<footnote><sup>a</sup> Centre de Recherche sur la Conservation, Muséum national d'Histoire naturelle, Ministère de la Culture, CNRS, Paris, France</footnote>

<footnote><sup>b</sup> Laboratoire d'Optique et Biosciences, CNRS, Inserm, Ecole polytechnique, Institut Polytechnique de Paris, Palaiseau, France</footnote>

<footnote><sup>c</sup> Université Paris-Saclay, Gif-sur-Yvette, France</footnote>

<footnote><sup>d</sup> Archéologie et philologie d'Orient et d'Occident, CNRS, École Normale Supérieure, Université Paris Sciences et Lettres, Paris, France</footnote>

<footnote><sup>e</sup> Communauté d'agglomération de l'Albiginois, médiathèque Pierre-Amalric d'Albi, Albi, France</footnote>

<footnote>* Corresponding author.
E-mail address: laurianne.robinet@mnhn.fr (L. Robinet).</footnote>
<figure><img src="image_5.png" /><figcaption>**Fig. 1.** *Mappa mundi* of Albi (fol. 57v) and the *Index of seas and winds* (fol. 58r) in the manuscript 29 preserved at the Médiathèque Pierre Amalric in Albi, France. Dimension 27 cm x 22.7 cm.</figcaption></figure>

The restoration campaign, in 1958, revealed changes in binding, dating back to the 17th and 18th centuries, when a handwritten *ex-libris* and a summary were added.

The *Mappa mundi* of Albi must not be considered alone, but as part of a two-sided document: a drawn map, on fol. 57v of the manuscript, and the *Index of seas and winds* (Latin *Indeculum quod maria vel venti sunt*), placed opposite, on fol. 58r. The index mirrors the shape of the map and is surrounded by a decorative three-strand braid seen from different sides. The braid's alternating colours reproduce those of the lands, seas, and frontiers on the map (Fig. 1). This map represents an oriented view of the inhabited world (where the East, *Oriens* in Latin, is at the top of the page). The lands correspond to the Roman Empire, centred around the Internal Sea (the Mediterranean with its component seas, including the Marmara, the Black Sea, and the Azov Sea). The maritime surfaces are painted green, except for five large islands, left uncoloured. The map does not correspond to a precise epoch, but compiles place- and people names of various times, until the Christianization of the Roman Empire and its final separation between East (Byzantium) and West (Rome) at the end of the 4th century CE. This world (called *orbis terrarum*, "circle of lands" in Latin) is surrounded by an ocean, coloured with the same green colour as the biggest rivers – the Paradisiac rivers (Nile/Geon, Indus/Phison, Tigris confused with Ganges) as well as the Rhine and the Rhone Rivers bordering Gaul. In some locations, on the shores as well as near the places where major cities were inscribed (like Alexandria, Carthage, Rome) or should have been inscribed (like possibly Milan), there are small circles, eventually filled with green: they could represent the first cartographic sign for showing the presence of people, in highly densely inhabited areas or on some maritime and ocean coasts, as interpreted by Dan [2]. These signs of habitability are absent on the southern coasts of Africa and the

northern coasts of Europe, regions still little known by Roman scholars at the end of Antiquity.

Land divisions are marked by simple or double lines, horizontal or vertical. The lands have the original colour of the parchment; their peculiar horseshoe shape is unique, but can be explained by the ancient tradition of the representations of the *orbis terrarum* (compared to a cloak by Eratosthenes, the inventor of geography) and by the constraints of this small rectangular manuscript to which one had to reduce a large and much more detailed map [2]. About 50 towns, regions, seas, and rivers, significant for Roman and Judeo-Christian history, as well as wind names taken from the texts which nourished the model of the map, are named. On the *Index of Seas and Winds*, names of 22 seas (parts of the Internal Sea – regrouping our Mediterranean and Black Sea – but also the gulfs of the surrounding ocean) are listed in a column of 24 lines at the centre of the page, following their general order from East (up) to the West (down), with 12 names of winds written radiantly, according to their geographical origin.

The *Mappa mundi* of Albi illustrates the knowledge about space and people in Late Antiquity, and its transmission between Gaul and Spain, after the fall of the Western Roman Empire. Some of the most important cities and empires of the Classical Antiquity (Babylon, Athens, Carthage, Macedonia, Alexandria, Rome) are mixed with names and signs related to Judaism and Christianinity, such as Jerusalem, Mount Sinai and the rivers of the Earthly Paradise mentioned in the *Genesis*, and identified with the real rivers of Egypt, Near East and India since the 4th–5th century CE. The *Mappa mundi* of Albi is probably an 8th-century copy, one of the oldest if not the oldest of its kind, derived and reworked after an older late-antique map. Dan suggests a 5th-century model, in France, possibly related to Eucherius, bishop of Lyon, who had an important contribution to the establishment of a Christian school
curriculum, after Jerome and Augustine and before Cassiodorus and Isidore [2].

## 2. Research aim

The manufacturing process, the use, and the conservation state of this exceptional manuscript are still largely unknown. Detailed observations and physicochemical analysis were performed on the map and the *Index* to identify the parchment, the ink and the colouring materials. The aim is to have a better knowledge of the *Mappa mundi* of Albi and, if possible, to contribute to the determination of its date and place of production. A multi-technique approach, combining non-invasive and micro-sample-based analyses at different length scales, was applied to the map and the *Index*. In parallel, the rest of the folios in Ms. 29 were examined to better understand the making of the *codex* and verify that the *Mappa mundi* was still in its original place in the manuscript. Three manuscripts also conserved at the Médiathèque Pierre Amalric in Albi and known or suspected to have been produced in the scripторium of Albi, only decades after Ms. 29, have also been examined for comparisons.

## 3. Materials and methods

The major part of the investigations was carried out on Ms. 29, dated to the 8th century and conserved in the Médiathèque Pierre Amalric in Albi (France), with a focus on folios 57v, the *Mappa mundi*, and 58r, the *Index of seas and winds*. For comparison, sample-based analyses were carried out on three additional manuscripts also conserved in the Médiathèque Pierre Amalric in Albi:

- RES Ms. 2, a canonical collection of Albi dated to 880-890, which is a copy of Ms. 364 from the region of Albi, today stored in the Toulouse library, and possibly the closest in date to the *Mappa mundi* of Albi (https://cecilia.mediatheques.grand-albigeois.fr/idurl/1/104);

- RES Ms. 38 bis, a canonical collection known as *Vetus Gallica* dated around 810. It was probably copied in Bourges, but was present in Albi from the end of the 9th century (https://cecilia.mediatheques.grand-albigeois.fr/idurl/1/113);

- RES Ms. 39, which contains a mixture of exegetic texts dated around 800 from one of the centers of Carolingian power. Its attribution to Albi is not confirmed (https://cecilia.mediatheques.grand-albigeois.fr/idurl/1/114).

Micro-samples were collected using the tip of a scalpel from five regions on the *Mappa mundi* of Albi, Ms. 29, fol. 57v: two from green coloured regions, s1 and s2, one within the double line around Jerusalem, s3 (Fig. S1 in supplementary material), and two on folio 57r, within the two circular stains, s4 and s5 (Fig. 2 and Fig. S1 in supplementary material). For comparison, micro samples were also collected from the green regions of Ms. 39 fol. 117v, and Ms. 2 fol. 1 and fol. 40.

For the analytical interpretation, two series of mock-up samples were prepared on parchment to collect reference spectra: a series with different binding media on its own: hide glue, egg white, egg yolk and a whole egg; and a series with different colouring materials mixed in hide glue: woad, weld leaves or buckthorn berries water extract, woad + weld leaves water extract and woad + buckthorn berries water extract (a detailed description of the mock-up preparation is given in supplementary material Fig. S2).

For the identification of the animal species of the parchment by proteomic analysis, minimum two folios per quire were sampled using a pair of fine tweezers in Ms. 29. As a result, a total of 25 folios were analysed in Ms. 29 (table S1 supplementary materials) and two folios originating from different quires were sampled in the other manuscripts: fol. 1 and fol. 40 in Ms. 2, fol. 8 and fol. 15 in Ms. 38bis, fol. 60 and fol. 118 in Ms. 39.

Photography of the map and the index was collected with a Nikon D800 camera in reflexion under visible and ultraviolet il-luminations, and in transmission using a Ceelite flexible lightsheet. Microscopic images were collected on the map and the index with a Dinolite digital microscope (AD 4113T-I2V) and Zeiss Axioscope A.1 microscope. Micro-samples were examined with an Axio Im-

<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Detail of the *Mappa mundi* of Albi observed under transmitted light (top) with mention of the two circular stains (red arrows s4 and s5) where micro-sampling was performed. Zoom-in (bottom): microscopic images of a hole and fold in the parchment folio collected in reflected light.</figcaption></figure>
ager D2m from Zeiss light microscope. The parchment thickness was measured with a digimatic micrometer Mytutoyo CLM-QMX with a force of 2.5 N. Measurements were taken on selected folios of quires 1, 2, 3, 8 and 9 of Ms. 29, in the middle of each folio edge (top, side and bottom) up to 25 mm from the border of the parchment folio. All measurements were repeated minimum three times and averaged.

X-ray fluorescence spectroscopy (XRF) measurements were collected using an Artax (INTAX, Berlin, Germany) equipped with molybdenum anticathode. A 0.6 mm collimator was used. It was operated at 45 kV, 600 µA. Direct analyses on the map and the index were carried out at a distance comprised between 5 and 6 mm from the instrument in a 400 s "live-time" period. The Artax device includes a Silicon Drift Detector X-Flash (RONTEC), an analyser and a software used for spectra acquisition, elements' recognition, background and peak areas calculation. The "collimator to sample" distance was adjusted using a digital video micro-camera attached to the measuring head of the system, close to the X-ray collimator.

Fiber-Optic Reflectance Spectroscopy (FORS) measurements were collected using a portable fiber spectrophotometer FieldSpec 4 (ASD) covering the visible and near-infrared wavelengths (350-2500 nm). The lamp and the collecting fibre optic were mounted on a stand with a 0-45° orientation to avoid any contact with the manuscript during the measurements. Spectra were collected with a resolution of 3 nm for 350-1000 nm and 10 nm for 1000-2500 nm ranges.

Mid-infrared spectroscopy measurements were collected in situ in different regions of the map with a portable Alpha spectrometer (Bruker) fitted with an external reflectance module. The instrument is equipped with a Globar SiC source and a DTGS detector. The measurements were carried out perpendicularly to the map over an area of around 7 mm, with a working distance of 15 mm. The spectra were collected in the 400-4000 cm⁻¹ spectral range, with a resolution of 4 cm⁻¹, and 128 scans. Kramers-Kronig transformation was applied to the reflectance spectra collected. Micro samples of the stain were analysed using a diamond cell on a Thermo-Nicolet infrared spectrometer coupled to a XL continuum microscope. The spectra were collected in the 400-4000 cm⁻¹ range with a resolution of 4 cm⁻¹.

Hyperspectral imaging was obtained using two devices for the collection of reflectance spectra in each point of the field of view for the visible near infrared (VNIR; 400-1000 nm) and the short-wave infrared range (SWIR; 900-2500 nm). The VNIR system consists of an Impector N10E spectrograph equipped with a CCD sensor composed of 1600 (spatial) x 1200 (spectral) pixels with a spectral resolution of 2.8 nm. The SWIR camera consists of an ImSpector N25E imaging spectrograph (Specimcorp, Finland) and a cooled, temperature stabilized MCT detector (9.6 mm detector having 320 (spatial) x 256 (spectral) pixels) with a spectral resolution of 10 nm. Both systems from Specim company work as a line scan camera providing full, continuous spectral data. The hyperspectral data cube is first normalised by using white and black images. A diffuse white reference (99 % reflectance spectralon®) covering the entire field of view of the detector was scanned both in each image/scan and separately to convert the resulting image cubes to reflectance factor. A dark reference was also acquired at each acquisition through a built-in shutter so as to quantify the electronic noise of the detector. Statistical analysis was applied to the VNIR and SWIR data cubes, especially principal component analysis (PCA) and spectral angle mapper (SAM). Calibration and data analysis were performed using ENVI software (Harris Corporation, USA). For the VNIR camera, a focal lens of 23 mm was used, with a 24 cm field of view and 0.2 mm spatial resolution. For the SWIR camera, a lens with a focal length of 15 mm, a 30 cm field of view, and 1 mm of spatial resolution was used. The working distance for both systems was around 47 cm, and a white cardboard was in-

stalled above the manuscript with a slot to protect it from light and direct heat from the halogen during the measurement.

A custom-built upright non-linear optical (NLO) microscope (multiphoton microscope) based on a femtosecond Ti:Sa laser (Mai Tai, SpectraPhysics) tuned to 860 nm was used as previously described [3]. Due to the non-planarity of the parchment folio, a 5x air objective (Nikon, AZ Plan Fluor 5x NA 0.5) with a 15 mm working distance was used for noncontact imaging of the parchment, resulting in nominal resolutions (FWHM) of 0.65 µm (lateral) and 4.0 µm (axial) (Fig. S3 in supplementary materials). Simultaneous two-photon excited fluorescence (2PEF) (GG400 high-pass filter, Schott) and second harmonic generation (SHG) (427/10 interferential filter, Semrock) signals were collected in the backward direction by using photon-counting photomultiplier tubes (P25PC, Electron Tubes). 2PEF and SHG signals are represented in false colours, respectively red and green. The acquisition pixel rate was 200 kHz, which corresponds to around one frame per second for 320 × 320 pixels wide images (1070 × 1070 µm² for 3.35 µm pixel size). The laser power at the sample surface was between 0.7 and 1.9 mW, without any observable damage in the studied samples. Image stacks were acquired with 5 µm axial steps with penetration depths ranging from 20 to 40 µm, depending on the local scattering properties of the parchment. The ratio of 2PEF and SHG signals was calculated to assess the degradation state of the collagen using a custom-written Matlab program [4].

Micro-Raman spectroscopy measurements were carried out on the microsamples using an Invia microscope (Renishaw) with a 532 nm or 785 nm laser (with 1800 or 1200 lines/mm grating respectively), 50 × (NA 0.75) or 100 × (NA 0.85) objectives and a power at the sample surface was around 1 mW (0.1-1 % at 532 nm et 1 % at 785 nm). Surface Enhanced Raman Spectroscopy (SERS) was carried out on a HE785 (Horiba-Jobin-Yvon) equipped with à 785 nm laser and a 685 lines/mm grating, and a Pelletier cooled CCD detector. The laser was focused on the sample using a x40 LWD objective (NA 0.45), with a laser power of approximately 10 mW at the sample. Silver colloids were prepared following the procedure of Lee and Meisel [5] by reduction of silver nitrate with sodium citrate, adapted from Van Elslande et al. [6]. The analytical procedure was the following: the sample is placed on a gold mirror and covered by a drop of around 10 µl of silver colloids and a 5 µl drop of KNO₃, an aggregating salt. The SER spectra were collected between 50 and 3300 cm⁻¹, for 1 to 4 s with 1 to 4 accumulations, depending on the sample.

Proteomic analyses were undertaken from some parchment fixtures (about 10 µg) sampled using a fine pair of tweezers on the hair side to identify the animal species. The peptide analysis is performed by MALDI-TOF after the digestion of the collagen by the trypsin enzyme, according to the Kirby method [7]. The detailed procedure is described in a previous publication [8].

The locations of all the point analyses (XRF, FORS, FTIR spectroscopies and NLO imaging) carried out in situ on the *Mappa mundi* fol. 57v and the *Index* fol. 58r and micro-sampling are presented in Fig. S1 in the supplementary material.

## 4. Results

The map and the index have been drawn on the parchment grain side, as can been seen from the remaining hair on the index. Visual observation of the map and the index revealed that the document has been highly used: the proofs are the faded brown ink of the writings and the lines, the missing footer corners restored with new parchment, and the presence of folds and creases in the parchment. A tab of parchment attached to the recto of folio 57 (Fig. S4 in supplementary materials), indicates that a restoration was carried out at some point in order to consolidate or reattach the folio. The map has a very shiny surface, unique in the
<figure><img src="image_7.png" /><figcaption>Fig. 3. Assembly of the parchment folios to visualize the skin originally used in some quires of Ms. 29. Blue arrows (on the right-hand side) correspond to the location of punches and horizontal fold on parchments.</figcaption></figure>

manuscript, suggesting a peculiar treatment of the surface. A green colouring material has been applied unevenly for the seas and rivers on the map and in two different hues in the frieze of the index. Two circular stains particularly visible under UV and transmitted light are observed on the top half of the map (pointed by red arrows in Fig. 2).

## 4.1. Parchment and manuscript structure

The previous codicological examinations of Ms. 29 identified ten quires [9,10]. By using the high-resolution digital images and the transmitted light photography collected during this study, we tried to understand how the quires and the bifolios were assembled and if the folios 57 and 58 were coherent with the rest of the manuscript. Additionally, the animal species of the parchment was identified and the parchment thickness was measured.

For proteomic analyses, the mass spectra of all the folios analysed in Ms. 29, Ms. 2, Ms. 38bis and Ms. 39 present ovine peptides markers, indicating that the parchment was made from sheep skin. The overall appearance of the folios, made of parchment of different quality, led us to distinguish three main parts in the Ms. 29: part 1, including quires 1 to 4 (fol. 1-fol. 32); part 2, including quires 5 and 6 (fol. 33-fol. 46); part 3, with quires 7 to 9 (fol. 47-fol. 71) (Fig. 3). The last folios in the manuscript are heavily degraded and incomplete; therefore, they could not be examined in detail, nor related to the others. Whilst in parts 1 and 2 the copyist used as much of the parchment surface and preserved the natural edges of the skin, the parchment bifolios in part 3 were cut to fit the dimensions of the manuscript (Fig. 3). In part 1, each quire is made of two bifolios cut from a single skin and assembled in quarto. In this part, the parchments have been roughly prepared, as seen from the important scraping marks, leading to a thick parchment of around 300-400 µm with great disparities (thickness values ranging from 200 to 550 µm within a folio, Table S2 in supplementary materials). In part 2, the parchment is more homogeneous, and fewer manufacturing marks are visible. However, the organisation of the quires is different, with three bifolios of similar appearance and another isolated bifolio. In part 3, that includes the Mappa mundi and the Index, the more careful finishing of the parchment led to a more homogeneous appearance. Therefore, the skin reconstruction was more difficult. The parch-

ment, similar along the three quires, was thinner, ranging from 200 to 300 µm, with a thickness of 200-270 µm for the Mappa mundi (fol. 57) and 250-320 µm for the Index (fol. 58) (Table S2 in supplementary materials). Double punches and a horizontal fold aligned with these punches are visible in all the bifolios. The observation of these marks under high magnification indicates that these are anterior to the decor application (Fig. 2 and highlighted by blue arrows in Fig. 3), meaning that these parchments originate from folios prepared for a larger manuscript, most likely blank, that was turned 90° to be reused [9]. Within part 3, the transmitted light photographs also revealed the presence of folds anterior to the writings and decor in bifolios fol. 50-fol. 51 in quire 7, and fol. 48-fol. 53, fol. 57-fol. 62 in quire 8. The folds and the similar finishing of the parchments in this group suggest that one skin has been used over several quires. A tentative assemblage of the quire in the manuscript is proposed in Fig. S5 of the supplementary materials.

Non-linear optical (NLO) microscopy of the map and the index has allowed us to observe the three-dimensional organisation of the collagen fibres, the main constituent of the skin, and its conservation state in different areas of the parchment. The collected NLO images combine second harmonic generation (SHG) signals, specific to well-preserved fibrillar collagen, and two-photon excited fluorescence (2PEF) signals emitted by fluorophore-containing materials such as degraded collagen, fat or dust [3]. The strong SHG signals in the images collected in central parts of the map (Fig. 4A) and on the index (Fig. S6 in supplementary materials) indicate a good preservation of the fibrillar collagen within the parchment. The two sides of the Mappa mundi's folio have a very different collagen fibre morphology: a dense collagen distribution with no clear organisation on the grain side (fol. 57v, Fig. S6A in supplementary materials) and well-defined thin fibres showing a more open structure on the flesh side (fol. 57r, Fig. S6B in supplementary materials). The fluorescent material observed between the fibres may correspond to fat residues present in larger amounts in sheep skin), degraded collagen, and maybe dust accumulated over time.

In some locations of the Mappa mundi, the images show a fluorescent material with a partially cracked surface, and the presence of line patterns that could correspond to brush strokes (Fig. S7 in supplementary materials). This material might be a coating that
<figure><img src="image_8.png" /><figcaption>**Fig. 4.** NLO images and computed images of the ratio 2PEF/SHG in different areas of the *Mappa mundi* of Albi and the *Index*. (A) SHG (green), 2PEF (red), merge of SHG and 2PEF signals, and pixel-wise ratio of the 2PEF signal to the SHG signal for areas at the centre of fol. 57v, and at the border of fol. 58r. (B) Computation of the pixel-wise ratio of the 2PEF signal to the SHG signal on different areas; the mean value of the ratio R over each image is indicated below each image. All the images are presented with the same Look-Up-Table (ratio between 0 and 7).</figcaption></figure>

has been applied over the parchment surface, likely responsible for
the shining surface observed on the map. On the edge of the index
folio, in an area that has probably been extensively manipulated,
the NLO images show a loss of SHG signals in the fibrous structure
combined with an increased fluorescence, suggesting a degradation
of the collagen (Figs. 4A and S6D). Previous work has shown that
the ratio of 2PEF to SHG signals can be used to quantify the col-
lagen state of degradation in parchment and that a ratio above 1
is indicative of an advanced state of collagen degradation [4]. This
ratio was calculated in different areas on the map and the index,
providing a ratio image and an average ratio value R (Fig. 4A and
4B). The values calculated for this ratio R are below 1 for all the
areas of the Mappa mundi (recto and verso) and also of the Index,
meaning that the fibrillar collagen is well-preserved, except for the

areas at the border of the index where R > 1: this confirms the
degradation of the collagen in this area, probably due to the regu-
lar manipulations.

4.2. *Decoration, lines and writings*

For the writing and tracing, X-ray fluorescence spectroscopy
analyses indicate the use of an iron gall ink with high iron con-
centration and traces of potassium, copper, zinc and lead (Fig. S8
in supplementary materials). The use of an iron gall ink is con-
firmed by hyperspectral imaging with the disappearance of the
tracing and writing in the infrared range. The composition is simi-
lar all over the map and the index. Hyperspectral imaging over the
visible range combined with principal component analysis (PC3,
<figure><img src="image_9.png" /><figcaption>**Fig. 5.** Hyperspectral image in the visible range after statistical analysis, PC3 of the map and the index in Ms. 29, revealing the iron-gall ink tracing. The vertical rectangular bands visible in each image correspond to a Mylar band used to maintain the parchment folios during analysis.</figcaption></figure>

third principal component) brings out the ink, which improves the readability of the text (Fig. 5). No preparatory drawings nor hidden writing could be seen, confirming that the reused parchment for the map and the index were initially blank. Because the manuscript could not be opened flat during the hyperspectral image collection, the region close to the binding could not be imaged sharply.

In the painted regions, we observed dark and light greens with light blue particles under magnification (Fig. S9 in supplementary materials). Compared to the parchment, no new chemical elements are detected by XRF: this excludes the use of a copper-based pigment (Fig. S8 in supplementary materials). The FORS spectrum suggests the presence of indigotin, the colouring molecule found in the plants of indigo and woad, according to the absorption peak at ca. 660 nm (Figs. 6B and C). This was confirmed by micro-Raman spectroscopy on samples s1 and s2 (Fig. 7A). The comparison of the FORS spectrum first derivative of different hues of the green colouring material on the map with reference spectra collected on painted mock-up displays a shift of the reflectance band to lower wavelengths associated with the dilution and the possible combination of indigotin with a yellow organic dye (Fig. 6C). The use of spectral angle mapper on the hyperspectral images helps to visualize the repartition of the different hues of green applied unevenly within the map and the index (Fig. 6A). The reflectance and first derivative spectra extracted from the visible hyperspectral images and used for the SAM statistical treatment are provided in Fig. S9 in supplementary materials.

SER spectra could be collected on sample s2, as well as on samples from the paint mock-ups prepared from the yellow dyes extracted from the berries of the buckthorn tree (Rhamnus cathartica) and weld. The SER spectra collected on the green sample from the map show a resemblance with the buckthorn berries spectrum (Fig. 7B), supporting our interpretation that the green colouring material on the Mappa mundi of Albi was prepared from a mixture of indigotin and a yellow natural organic dye. In the manuscripts used for comparison, however, the green colouring materials identified

by micro-Raman spectroscopy appears to be copper based compounds due to the presence of a copper degradation product atacamite in Ms39 and possibly an organocopper complex in Ms. 2 (Fig. S10 in supplementary materials) [11].

Infrared reflectance spectra collected in the different regions of the Mappa mundi display the characteristic bands of protein at 1654 and 1546 cm⁻¹ (Amide I and II), a strong band around 1445 cm⁻¹ and 875 cm⁻¹ corresponding to calcium carbonate, as well as strong CH₂, CH₃ stretching vibrations at 2850 and 2920 cm⁻¹, suggesting the presence of fats, common in sheep-skin parchment (Fig. 8 and infrared reference spectra of calcite in Fig. S11). A sharp peak at 1578 and 1543 cm⁻¹ suggests the presence of calcium stearate or palmitate, calcium soaps possibly from the reaction of these fatty acids with the calcium carbonate applied on the parchment during manufacturing [12]. This is confirmed by micro-Raman spectroscopy on the microsamples collected on the map (Fig. 7C), in particular sample s3 whose spectra match the spectra of calcium palmitate [12]. Within the microsamples, micro-Raman spectroscopy also identified calcium carbonate (v(CO₃⁻) at 1086 cm⁻¹), calcium sulphate (v(SO₄²⁻) at 1008 cm⁻¹), starch (475 cm⁻¹ (Fig. 7D, Raman reference spectra in Fig. S12), as well as an organic compound with intense bands at 1336 and 1374 cm⁻¹ that remains unidentified (Fig. 7C). Whilst calcium carbonate and calcium sulphate most likely originate from the use of lime and chalk for the parchment manufacturing, the starch comes from a recent addition, possibly as part of the shiny varnish applied as a protective layer or a conservation treatment.

Interestingly, another peculiar treatment seems to have been applied in the upper right part of the map, in the Eastern part of the Mediterranean, as it is the only region prominent in the infrared hyperspectral image (Fig. 9). In the visible range, some green colouring material is detected in the lower part of the double line surrounding the names of Jerusalem and Judea. Close observation of this area under UV and transmitted light suggests that this part has been scrapped, possibly to correct or to reinforce the green colouring material initially applied over it. Raman spectroscopy of
<figure><img src="image_10.png" /><figcaption>**Fig. 6.** Characterization and distribution of the green colouring material on the *Mappa mundi* of Albi and the *Index of seas and winds*. (A) Hyperspectral image in the visible range after statistical analysis with Spectral Angle Mapper showing the repartition of the green colouring material; (B) FORS spectra in reflectance; (C) FORS first derivative spectra of the green region on the map compared to reference spectra collected on painted mock ups.</figcaption></figure>

the micro-sample from this area identified the presence of calcium carbonate and calcium palmitate, with isolated particles of iron oxide and carbon black which may be contaminants (not shown).

Finally, the two round stains showing up in the upper part of the map (highlighted by the red arrows in Fig. 2), have been identified by micro infrared spectroscopy as beeswax from the analysis of samples s4 and s5.

**5. Discussion**

Detailed observation and physicochemical analyses of the *Mappa mundi* of Albi and its manuscript shed new light on its manufacturing, life, and condition. The map and the *index* belong to a group of three quires in the manuscript (quire 7: fol. 47-fol. 55; quire 8: fol. 56-fol. 63; quire 9: fol. 64-fol. 71), whose parchments have been prepared and assembled similarly. These quires, which originate from a larger blank set of parchment reused with a different orientation, with trimmed folios, homogeneous and thinner leaves, show a greater finishing when compared to the other quires. This superior quality of the parchment used for a smaller codex than the one for which it was cut originally may suggest

that special attention was given to this part, possibly to accommodate the coloured folios. Besides the *Mappa mundi* and the *Index*, the quires contain moral, historical and geographical texts that were fundamental in the Early Medieval education of monks [2,9,13,14].

The manuscript has been prepared on a sheep skin parchment, which was very common in the Late Antiquity. During the Early Middle Ages, it remains frequent in the Albi region, as shown by the identification of the animal species of the parchment used for the other manuscripts originating from Albi. The heterogeneity of the parchment's thickness, however, and the presence of holes that were not repaired suggest that the economic conditions of the scriptorium in which the manuscript was copied were not so favourable as those of other Late Antique manuscripts preserved to our day [15]. The use of fine parchment, with a different orientation, could be a consequence of the need to put together all the available pieces to copy this 'encyclopaedic' schoolbook. The calcium carbonate identified at the surface was likely applied during the preparation of the parchment to help the absorption of the fats, present in high quantities in sheep skins [16,17], and to give a whiter appearance to the support for writing and drawing. This
<figure><img src="image_11.png" /><figcaption>**Fig. 7.** Raman spectra of the *Mappa mundi* of Albi micro-samples (MMA in black) with reference spectra (in blue). (A) Spectra of the blue particles; (B) SERS spectra of the yellow dye; (C) spectra of the organic media; (D) spectra of the white particles.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>**Fig. 8.** Infrared reflectance spectra with Kramers Kronig transformation of the green colouring material and the parchment on the *Mappa mundi* of Albi.</figcaption></figure>

corresponds to the Roman 'white parchments' (Latin *candida membrana*), well-known to Isidore of Seville in the 7th century (*Etymologies* 6.11.2).

A characteristic feature in the map and the *index* is the widespread use of a green colouring material prepared from a

mixture of indigotin, originating from indigo (Latin *lulax*, Greek λουλάκιον, from plants like *Indigofera tinctoria* L.) or woad (*Isatis tinctoria* L.), with a yellow natural organic dye possibly extracted from buckthorn, a fruit grain abundant in Mediterranean countries. This composition goes back to Antiquity: the 4th-century Stockholm papyrus written in Greek recommends the preparation of green pigments like the chrysoprase from indigo and celandine [18]. A late Byzantine recipe from the manuscript A6 in the Erlangen Universitätsbibliothek (fol. 18v) refers to a similar composition of a green pigment from indigo, but lets the artisan choose the "yellow colorant" [17]. In any case, this vegetal mix observed on the *Mappa mundi* differs from the copper-based green pigment used in the other manuscripts made in Albi later on, in the early and mid-9th century.

The comparison with other studies on manuscripts from different periods and places in Europe is informative. Indigo is known as a commercial colorant (Johannes Lydus, *On the months* 1.21, 6th century) and was identified in manuscripts from the 5th century onwards (like the *Vergilius Vaticanus*, and the *Quedlinburger Itala* [17]). Its use continues in the Early Medieval scriptoria, between the 8th and the early 10th century [19–22]. Recipes for the fabrication of indigo-based colorants inspired from Hellenistic and Roman sources are well attested in this period – for example in the *codex Lucensis* 490 (dated between the end of the 8th and the beginning of the 9th century, preserved in the Feliniana Chapter Library of Lucca [23]). Claude Coupry published a clear chronology of the use
<figure><img src="image_13.png" /><figcaption>**Fig. 9.** Detail images of the region around Jerusalem in the *Mappa mundi* of Albi, Ms29 under different illumination: (A) reflected white light, (B) Ultraviolet, (C) transmitted light, (D) visible hyperspectral + PCA, (E) visible hyperspectral + SAM, (F) near infrared hyperspectral.</figcaption></figure>

of blue pigments in Western medieval manuscripts: indigo is used in the most ancient manuscripts; lapis-lazuli is only used from ca. 800 onwards, while azurite is used even later, from the 10-11th century onwards [19,24]. In the 8th century, the green colour was made either using copper-based pigments, such as verdigris, or from a mixture of indigo with a yellow pigment, like orpiment, known as “vergaut” [20-22,25]. Both green compounds can sometimes be found in a single manuscript. To our knowledge, despite the antiquity of the recipe, the use of a mixture of indigotin with a yellow natural organic dye has not been evidenced in other manuscripts from this period. Although the pigment was widely used for textiles and inks since Antiquity, this is the earliest example in Albi, where all the other manuscripts use copper-based pigments. Toulouse, close to Albi, was well-known for its woad plant (*Isatis tinctoria*) cultivation only from the 14th century onwards [26]. The identification of indigotin could suggest that the *Mappa mundi* was made in the Albi region, and that the indigotin used on the *Mappa mundi* could originate from woad cultivated in the region, centuries before its modern fame. However, one needs to be careful: indigotin was an important product of trade in Late Antiquity and these analyses cannot give a definite answer about its origin in early Medieval times.

The parchment is well preserved; the only damages that can be seen are due to heavy manipulation (including the map and the *index*), with folds and creases in the parchment, degradation of the collagen on the edge, and beeswax stains probably from a candle (suggesting reading in the dark). The ink for the lines and writings has faded, possibly due to extensive exposure to light.

The document suffered several interventions at different moments in its history. The modification of the area around Jerusalem is the most intriguing one. The double line that was initially green likely corresponds to the aquatic border of the Promised Land, the centre of Judaism, the birthplace of Christianity. As explained by Dan, the green line corresponded to a series of real rivers, including not only the Jordan River (with its tributaries Jor and Dan) but also the Orontes River to the north (identified by the presence of the toponym of Antioch) and the Wadi El-Arish, to the south, near

Gaza and the border between Egypt and Judea [2]. These rivers, now represented on the *Mappa mundi* as one circular water flow, represent the water border crossed by the Israelites who came from Egypt through Sinai (normally to the South-West of ancient Syria) but curiously entered the Promised Land from the East (according to the Biblical book of Joshua 1:1-4). We do not know if the readers of the Albi manuscript were aware of this geographical anomaly of crossing the Jordan (from the East) while coming from Egypt (therefore from the West), but the map certainly allowed them to understand the biblical text and to visualize the conquest of Canaan. This final part of the Jewish exodus was much studied by the Jews and the Christians fighting against the Islamic conquests of the Mediterranean [27]. We cannot know when the Jewish border was changed or underlined on the map, but this intervention must be related to the importance of the terrestrial Jerusalem and of the Holy Land in the religious teaching and contemplation of a Biblical map. The correction could make Judea and Jerusalem immediately visible for all those willing to compare the drawing with the Old Testament and with the Early Christian writings (like Orosius, whose geographical introduction to the *Histories against the Pagans* inspired the prototype of the map and follows the map in this manuscript; one can mention also Eucherius, Jerome and Isidore, whose texts reflect analogous mental maps). If the change was made several centuries after the original drawing, it could be an update of the early Medieval Albi *mappa mundi* to the later Medieval model of maps, which put the Holy Land and Jerusalem in a central position [28,29]. Whatever the date, the monk reading the manuscripts could have been tempted to underline the region where Christ lived and to make it striking for anyone opening the page.

Later modifications were made as part of the conservation treatment of the two folios, such as the addition of new parchment at the bottom page corners, the consolidation of the binding with the addition of a parchment tab, and possibly the application of varnish on the surface of the map as a protective measure, giving the shiny appearance it still has today. These different interventions are not mentioned in the report for the conservation
treatment carried out in 1958 by the Toulouse municipal library [30]. This means that these are anterior to this date, possibly going back to the 17th or the 18th century, when a new binding was made.

## 6. Conclusion

The *Mappa mundi* of Albi is one of the two oldest polychrome world maps made in Western Europe, which have been preserved to our day (UNESCO Memory of the World Register in 2015). This study complements the historical and philological articles published during the last years under the impetus of Jocelyne Deschaux, to improve our knowledge of the manufacturing technique of this document and its conservation state [2,13].

The observations confirmed that the *Mappa mundi* and the *Index* (which faces and completes the drawing in the manuscript), belong to one of the three parts of the manuscript, made of parchment of superior quality. Hyperspectral imaging in the visible and near-infrared ranges combined with statistical data treatments emphasised the spatial distribution of the inks and the green colouring materials, but also revealed peculiar areas – such as the circular drawing around Jerusalem and Judea. Prominent to the naked eye, this outline is now physically and chemically proven to be a correction of the original map, confirming its use as a support for study and contemplation in the long run. From the combination of the different chemical analytical techniques, we identified the use of a mixture of indigotin and a yellow dye to make the different hues of green: this is the first chemical evidence of the mix, otherwise well attested by the Greek and Latin recipes of pigments, transmitted from Antiquity to Medieval times. The parchment was prepared from a sheep skin. The fat remaining from the animal likely reacted with the chalk preparation and produced calcium soaps. Nonlinear optical microscopy helped visualise the morphology of the collagen fibres in the parchment and quantified their conservation state. These measurements revealed that the collagen in the map and the *index* is well-preserved, except for the heavily manipulated edges of the folio. This material study also shows several changes of the manuscript throughout its long history, like the modification of the area surrounding Jerusalem, the presence of wax deposits, or the application of a shiny varnish, which is probably more recent. These new data on the constitutive materials might encourage new reflections from philologists and historians on this unique document and, more generally, on the so-called ‘Dark Age’ during which the manuscript was made: this was a time when the Roman world drawn on the map was only a memory, very different from the reality of the Arab conquests in Spain and Southern France.

## Acknowledgments

The authors wish to acknowledge Christine Andraud, Bertrand Lavédrine and Stéphane Vaïdelich from the CRC for their support with the analyses of the manuscript, Dan Kirby from Boston University for introducing us to proteomic analyses, and carrying out the first measurements on the parchment, as well as Ludovic Belot-Gurlet at the Monaris laboratory for providing access to their equipment to carry out SERS analyses. We are also grateful to Mrs Pascal Heurtel from the library of the National history museum in Paris and Mrs Delphine Gallot from the library of the Polytechnique school for their help within these analytical campaigns.

## Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.culher.2025.05.013.

The raw data from the physicochemical analyses of the *Mappa mundi* of Albi and the *Index* are accessible from https://doi.org/10.48579/PRO/T2VBXF.

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