For several years now, heritage sciences have been experiencing a particularly significant boom. This deeply interdisciplinary field of research aims to foster dialogue between the humanities and natural sciences with a view to improving our knowledge of heritage objects, whether they be parchments, works of art, or artifacts discovered during excavations.

Manuscripts bear witness to ancestral practices and know-how, which unfortunately are poorly documented. It is still unclear why legal documents were preferably written on sheepskin parchment in England from the 13th century until 1925. Among the hypotheses put forward is the fact that sheepskin is whiter, and therefore more attractive, but above all that documents written on it were considered unforgeable due to the tendency of sheepskin to delaminate (any malicious attempt to erase the text would thus be revealed). This delamination property was exploited because it allowed the production of high-quality writing surfaces. It was also used to prepare strong repair pieces used to fill any tears that appeared during the parchment manufacturing process. Understanding why sheepskin delaminates is of interest in the context of traditional parchment preparation techniques, offering valuable insights into the interaction between animal biology, craftsmanship, and historical needs.

Delamination is the phenomenon whereby the inner layers of the skin separate along their interface as a result of mechanical stress. The diagram (a) below shows the structure of the skin, which consists mainly of the epidermis, dermis, and hypodermis. The dermis is divided into two layers, the papillary dermis and the reticular dermis, which contain hair, hair follicles, and sebaceous glands. 

During the parchment manufacturing process, a step following liming involves scraping the skin to remove the hair. This step crushes the sebaceous glands, releasing fats and creating a void where the hair was located (diagram b). 

The study showed that delamination occurs within the papillary dermis itself, in this structurally weakened area, rather than at the papillary-reticular junction as previously assumed. 

The unique nature of the delamination process in sheepskin is highlighted by the skin structure, which differs from that of other animals (calves, goats) used to make parchment, as it has a high fat content associated with a large number of primary and secondary hair follicles. In the study, the presence of fats was confirmed using Raman spectroscopy.

This study combines experimental archaeology and advanced analytical techniques, including scanning electron microscopy (SEM) and micro-Raman spectroscopy, to characterize the delamination process and the adhesion of repair pieces on experimentally produced sheepskin parchment. It benefits from the expertise in archaeometry, biology, chemistry, and physics of the researchers involved.

Beyond its visual and structural implications, delamination has contributed to promoting the use of sheepskin for prestigious documents, improving the surface properties of parchment. The study of the interaction between metal-gallic ink and delaminated sheepskin (wetting experiments) showed that ink diffusion and writing quality are improved, a key finding that provides insight into how surface morphology and composition influence writing performance.

At UNamur, Marine Appart, a PhD student in physics, is conducting this multidisciplinary research on the archaeometry of delamination and repairs on a sheepskin parchment under the supervision of Professor Olivier Deparis (Department of Physics, NISM Institute). 

Also part of the UNamur team are:

• Professor Francesca Cecchet (expert in Raman spectroscopy), Department of Physics, NARILIS and NISM Institutes
• Professor Yves Poumay (skin specialist), Department of Medicine, NARILIS Institute
• Dr. Caroline Canon (histology specialist), Department of Medicine
• Nicolas Gros (PhD student in heritage sciences), Department of Physics, NARILIS and NISM Institutes

Other international experts

• Professor Matthew Collins (world expert in biomolecular archaeology, Department of Archaeology, The McDonald Institute, University of Cambridge, Cambridge, UK)
• Jiří Vnouček (curator and expert in parchment production, Preservation Department, Royal Danish Library, Copenhagen, Denmark)
• Marc Fourneau (biologist) 

This study and the resulting article were inspired by the delamination experiments conducted in 2023 by Jiří Vnouček during a symposium in Klosterneuburg, Austria, in which Prof. Olivier Deparis participated. The symposium was organized by Professor Matthew Collins as part of the ABC and ERC Beast2Craft (B2C) projects.

But it all began in 2014, when the Pergamenum21 project, dedicated to the transdisciplinary study of parchments, was launched.  Pergamenum21 is a project of the Namur Transdisciplinary Research Impulse (NaTRIP) program at the University of Namur. The project received an additional grant in 2016 from the Jean-Jacques Comhaire Fund of the King Baudouin Foundation (FRB).

The projects and events followed one after another, including: 

• May 2014: a transdisciplinary seminar on parchment, the scientific techniques used to characterize this material, and historical questions at the Mauretus Plantin Library (BUMP)
• May 2017: "Autopsy of a scriptorium: the Orval parchments put to the test of bioarchaeology," a transdisciplinary research project co-financed by the University of Namur and the Jean-Jacques Comhaire Fund of the King Baudouin Foundation
• April 2019: a publication in Scientific Reports, Nature group - Jean-Jacques Comhaire Prize: discovery of an innovative technique based on measuring the light scattered by ancient parchments. This technique makes it possible to characterize, in a non-invasive way, the nature of the skins used in the Middle Ages to make parchments
• September 2020: a residential workshop on making parchment from animal skins at the Domaine d'Haugimont – a first in Belgium
• July 2022: a new project on parchment bindings for the restoration workshop at the Moretus Plantin University Library (BUMP) thanks to the Jean-Jacques Comhaire Fund of the King Baudouin Foundation.
• September 2024: a residential symposium-workshop at the Domaine d'Haugimont on the theme of the physicochemistry of parchment and inks using experimental and historical approaches 

Overall, the work of Marine Appart and her colleagues clarifies the structural and material factors that make sheepskin parchment susceptible to delamination and offers new insights into the surface properties of this ancient writing material. UNamur is now establishing itself as a major player in parchment research.

Professor Olivier Deparis, along with several of the researchers involved in this research, are also working on the ARC PHOENIX project.  This project aims to renew our understanding of medieval parchments and ancient coins. Artificial intelligence is used to analyze the data generated by the characterization of materials. This joint study will address issues related to the production chain and the use of these objects and materials in past societies. 

This is a thread that Jean-François Nieus has been pursuing for some twenty years, as part of research into the uses of writing, which elevates documents to objects of history in their own right. This approach, developed over several decades, sheds light on medieval society in all its dimensions: cultural, of course, but also social, political, economic, and religious. "Writing was rare in the early Middle Ages. It gradually gained importance in social practices, with a clear shift in the 12th and ^13th centuries—i.e., during the High Middle Ages—when people began to write much more and diversify the formats and functions of writing," he explains. 

Jean-François Nieus is particularly interested in documentary productions associated with the exercise of princely power and seigneurial management, within an area stretching from the Anglo-Norman world to the Southern Netherlands. Princely and noble archives are essential for understanding the relationships of domination in the so-called "feudal" age, that of territorial principalities and seigneurial lordship, but also issues of family identity and lineage, which were central concerns of the aristocracy. "After the mid^-12th century, most noble families began to keep archives, initially consisting of a few received charters, but soon enriched with their own administrative productions. Although the majority of these secular collections have now disappeared, there is evidence of their existence," he explains. The vicissitudes of the history of the great families and the French Revolution contributed to the loss of these fragile documents, so that today only a handful of archives from ^the 12th and 1^3th centuries remain.

Those studied by Jean-François Nieus nevertheless cover a wide range of types: they include "chartriers" (collections of original charters), "cartulaires" (collections of copies of charters), "formulaires " (collections of model charters and letters), "censiers" (descriptions of the property and income belonging to a seigneury), lists of vassals and fiefs, accounts, etc.

Jean-François Nieus also carries out critical editing work. He will soon publish the archives of the Béthune family (now Pas-de-Calais), as well as those of a small abbey linked to these lords, Saint-Jean-Baptiste de Chocques, whose collection, destroyed during the French Revolution, he is reconstructing.

This patient and meticulous work of discovery, deciphering, studying, and publishing sources that are sometimes very scattered helps to restore the memory of an era and enrich the documentation available to researchers.

In addition to administrative writings, Jean-François Nieus is also passionate about an auxiliary science of history: "sigillography," the study of seals. These small wax discs attached to official documents provide a unique window into the cultural representations of the time. In particular, they show how, after 1066, under the influence of William the Conqueror, a new image emerged: that of a knight on his galloping horse, weapon in hand. This motif, which was completely new at the time, quickly spread among princes and nobles, becoming a powerful symbol of chivalry.

Following this evolution, Jean-François Nieus also traces the spread of coats of arms—heraldry—which he sees emerging in the early ^12th century in northern France and the Anglo-Norman region. Equestrian seals, heraldic signs, and chivalric rites such as tournaments thus formed a cultural community that invented and asserted itself in this area.

If the Middle Ages fascinate Jean-François Nieus so much, it is undoubtedly because of their strangeness: a world very distant from our own, often distorted by stereotypes. "It's a difficult period to popularize because it's so different from our own, even though, in reality, we owe it a great deal. What's more, perceptions of it are marred by numerous clichés, and the general public still views it very negatively, as reflected in everyday language by the sinister adjective 'medieval,'" observes the researcher.

What are the reasons for this negative view? The perspective of intellectuals in subsequent eras, who saw it as the origin of all the archaisms they wanted to combat. Nineteenth-century historians, who gave the discipline its scientific foundation, also passed on erroneous interpretations, which contemporary research is gradually correcting. 

Jean-François Nieus appeared in episode 1 of season 3 of the documentary series "Batailles de légende" (Legendary Battles), which focused on the great battle of Bouvines between King Philip II Augustus of France and a coalition led by King John of England (1214).

To understand how the transition to Christianity came about, researchers generally turn to the great authors, and in particular Saint Augustine, the key figure of Christian antiquity whose writings have been preserved the most. Alongside his best-known works (such as The City of God or The Confessions), Saint Augustine is also the author of short treatises on practices such as marriage or baptism. "In my early post-doctoral research, I sought to understand how these short texts by Augustine, and other North African sources, circulated in the West between late antiquity and the early Middle Ages. This was a period of religious mixing when the first Christian communities were setting up systems of initiation and teaching", explains Matthieu Pignot.

Very quickly, the researcher's interest also turned to anonymous or pseudepigraphic texts (erroneously attributed to a known author), which had fallen into oblivion in favor of writings by authors, and which also addressed these questions of religious education. "This is the starting point for my research project. These texts are difficult to study because, circulating under several names, we don't know their true author. We don't know who wrote them, and we know little about their ancient and medieval transmission. It is precisely these grey areas that make them so interesting", continues the historian.

To address this question, Matthieu Pignot starts from two bodies of texts: on the one hand, a collection of 80 sermons wrongly attributed to Fulgence of Ruspe and, on the other, a Latin translation of an anonymous collection of Greek philosophical maxims by Rufinus of Aquileia (IV-V^th century), an author who played an important role in the transmission of Greek thought in late antiquity in the West.

The methodology favored by Matthieu Pignot for this research involves the use of digital publishing. The aim? "To bring into existence and enhance the value of these texts, which don't have the privilege of having an author's name, and some of which haven't even been printed. What's more, stylistic and linguistic analysis tools will perhaps make it possible to provide clues about the author, or at least to group texts together, based on recurring writing tics."

With this project, Matthieu Pignot also aims to develop the automated manuscript transcription component, which is still under development. "My aim is to contribute to the improvement of these tools through my own transcriptions and to participate in the dynamic of interest in medieval manuscripts in archives and libraries", concludes the researcher.

Matthieu Pignot is a member of the research center PraME("Pratiques médiévales de l'écrit"), part of the research institute PaTHs ("Patrimoines, Transmissions, Héritages"). He also collaborates with the Institut d'études augustiniennes (Paris) and the University of Nijmegen.

I was fascinated by the research field of one of my professors, Guy Demortier. He was working on the characterization of antique jewelry. He had found a way to differentiate by PIXE (Proton Induced X-ray Emission) analysis between antique and modern brazes that contained Cadmium, the presence of this element in antique jewelry being controversial at the time. He was interested in ancient soldering methods in general, and the granulation technique in particular. He studied them at the Laboratoire d'Analyses par Réaction Nucléaires (LARN). Brazing is an assembly operation involving the fusion of a filler metal (e.g. copper- or silver-based) without melting the base metal. This phenomenon allows a liquid metal to penetrate first by capillary action and then by diffusion at the interface of the metals to be joined, making the junction permanent after solidification. Among the jewels of antiquity, we find brazes made with incredible precision, the ancient techniques are fascinating.

In fact, this was one of Namur's fields of research at the time: heritage sciences. Professor Demortier was conducting studies on a variety of jewels, but those made by the Etruscans using the so-called granulation technique, which first appeared in Eturia in the 8th century BC, are particularly incredible. It consists of depositing hundreds of tiny gold granules, up to two-tenths of a millimeter in diameter, on the surface to be decorated, and then soldering them onto the jewel without altering its fineness. So I also trained in brazing techniques and physical metallurgy.

I applied for a position as a physicist at CERN in the field of vacuum and thin films, but was invited for the position of head of the vacuum brazing department. This department is very important for CERN as it studies methods for assembling particularly delicate and precise parts for accelerators. It also manufactures prototypes and often one-off parts. Broadly speaking, vacuum brazing is the same technique as the one we study at Namur, except that it is carried out in a vacuum chamber. This means no oxidation, perfect wetting of the brazing alloys on the parts to be assembled, and very precise temperature control to obtain very precise assemblies (we're talking microns!). I'd never heard of vacuum brazing, but my experience of Etruscan brazing, metallurgy and my background in applied physics as taught at Namur were of particular interest to the selection committee. They hired me right away!

CERN is primarily known for hosting particle accelerators, including the famous LHC (Large Hadron Collider), a 27 km circumference accelerator buried some 100 m underground, which accelerates particles to 99.9999991% of the speed of light! CERN's research focuses on technology and innovation in many fields: nuclear physics, cosmic rays and cloud formation, antimatter research, the search for rare phenomena (such as the Higgs boson) and a contribution to neutrino research. It is also the birthplace of the World Wide Web (WWW). There are also projects in healthcare, medicine and partnerships with industry.

For my part, in addition to developing vacuum brazing methods, a field in which I've worked for over 20 years, I've worked a lot in parallel for the CLOUD experiment. For over 10 years, and until recently, I was its Technical Coordinator. CLOUD is a small but fascinating experiment at CERN which studies cloud formation and uses a particle beam to reproduce atomic bombardment in the laboratory in the manner of galactic radiation in our atmosphere. Using an ultra-clean 26 m³ cloud chamber, precise gas injection systems, electric fields, UV light systems and multiple detectors, we reproduce and study the Earth's atmosphere to understand whether galactic rays can indeed influence climate. This experiment calls on various fields of applied physics, and my background at UNamur has helped me once again.

I was also responsible for CERN's MACHINA project -Movable Accelerator for Cultural Heritage In situ Non-destructive Analysis - carried out in collaboration with the Istituto Nazionale di Fisica Nucleare (INFN), Florence section - Italy. Together, we have created the first portable proton accelerator for in-situ, non-destructive analysis in heritage science. MACHINA is soon to be used at the OPD (Opificio delle Pietre Dure), one of the oldest and most prestigious art restoration centers, also in Florence. The accelerator is also destined to travel to other museums or restoration centers.

ELISA uses the same accelerator cavity as MACHINA. The public can observe a proton beam extracted just a few centimetres from their eyes. Demonstrations are organized to show various physical phenomena, such as light production in gases or beam deflection with dipoles or quadrupoles, for example. The PIXE analysis method is also presented. ELISA is also a high-performance accelerator that we use for research projects in the field of heritage and others such as thin films, which are used extensively at CERN. The special feature is that the scientists who come to work with us do so in front of the public!

I remember that in 1989, I finished typing my report for my IRSIA fellowship in the middle of the night, the day before the deadline. It had to be in by midnight the next day. There were very few computers back then, so I typed my report at the last minute on one of the secretaries' Macs. One false move and pow! all my data was gone - big panic! The next day, the secretary helped me restore my file, we printed out the document and I dropped it straight into the mailbox in Brussels, where I arrived after 11pm, in extremis, because at midnight, someone had come to close the mailbox. Fortunately, technology has come a long way since then...

The proximity between teaching and research inspires and questions. This enables graduate students to move into multiple areas of working life.

Come and study in Namur!

Serge Mathot (May 2025) - Interview by Karin Derochette

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