Encre, parchemin et papier à Chartres au XIVe siècle Les matériaux de l’écrit au prisme des sciences expérimentales

International audienceInscrit dans une perspective transdisciplinaire, au carrefour des sciences humaines et des sciences expérimentales, le projet de recherche EVAS avait pour ambition de forger une nouvelle méthodologie d’étude des pratiques d’écriture médiévales en mêlant un examen codicologique traditionnel à une analyse en laboratoire des matériaux constitutifs du document écrit. L’enquête a porté sur le cas de Chartres dans la seconde moitié du xive siècle et a livré plusieurs enseignements importants. Alors que les travaux récents ont démontré que la peau de veau a été majoritairement utilisée dans l’espace français pour produire des manuscrits de bibliothèque, nos recherches indiquent que, au sein de ce même espace, les documents d’archives plus « ordinaires » ont toujours été écrits sur peau de mouton. En outre, une analyse élémentaire des encres a permis de déterminer à partir de quels sels métalliques ces dernières avaient été fabriquées. Partant, il a été possible de distinguer l’usage de différentes familles d’encre à Chartres au xive siècle, et ce même dans les cas où ces encres présentaient des aspects visuels similaires. L’article présente la méthodologie adoptée ainsi que les principaux résultats obtenus

Dégradation de schistes argileux fossilifères (Bassin d’Autun, France, Permien), partie III : pyrite framboïdale et soufre identifiés comme cause principale des efflorescences

International audienceFossil-bearing shale specimens that include sulfides are chemically reactive and sometimes also mechanically fragile. This decay is provoked by iron sulfate efflorescence resulting from the oxidation of sulfide compounds. The processes underlying these degradations are poorly known, thus impeding the elaboration of curative or preventive treatments. The present contribution aims to identify the origin of museum specimen alterations. It focuses on the Flouest collection housed at the Muséum national d'Histoire naturelle (MNHN, Paris, France) and originating from the Autun Basin (Saône-et-Loire, France; Permian). To evaluate the alteration of MNHN specimens, it appeared necessary to compare their composition with that of unaltered shale so as to identify chemical changes occurring during ageing. Therefore new material was collected in the Autun Basin, among others on the locality of Muse that corresponds to the same lithostratigraphic unit than that of the MNHN specimens. This work is divided in three parts. The two first, presented elsewhere, deal with the composition of the shale matrices and led to the conclusion that these matrices could not account for the large iron(II) sulfate efflorescence provoking damage on the MNHN specimens. The last part of this work, presented here, focus on artificial age-ing experiments performed on new shale material. Most of the alterations observed on artificially aged samples correspond to dispersed crystals of calcium sulfate (gypsum). Similar crystals may be found on MNHN specimens, but they are relatively few and sporadically distributed. They are thus considered as damage of secondary importance with respect to iron sulfate efflorescence. These latter could be reproduced on three samples only (upon the 142 aged samples). They were also found on a copro-lite and on a wood remain that had got severely damaged in ambient conditions within a few months after their excavation. On all these samples iron sulfate had grown on brownish layers consisting in crystals of framboidal pyrite (1 to 3 m) and eventually sulfur (20 to 50 m). These brownish layers are associated to thin maceral layers probably because of bacterial activity: during fossil diagenesis, bacteria need organic matter for their metabolism to produce hydrogen sulfide, a precursor of sedi-mentary pyrite formation. Most of the damaged specimens of the Flouest collection show as well a thin maceral layer nearby iron(II) sulfate efflorescence. On one of them, this layer is particularly thick. It corresponds to vitrinite and shows in some areas a brownish aspect. The topology of this surface (observed with scanning electron microscopy) shows numerous small holes (< 2 m) and large holes (10–20 m). This morphology is compatible with a former occurrence of isolated grains and aggregates of framboidal pyrite. These observations suggest that iron sulfate efflorescence was provoked by th

Application of Arrhenius law to DP and zero-span tensile strength measurements taken on iron gall ink impregnated papers: relevance of artificial ageing protocols

International audienceIron gall inks (IGI) were largely used for writing until the nineteenth century. Under certain circumstances, they provoke a substantial degradation of their cellulosic support.It was shown in a previous works thatc ombination of oxygen and iron largely impacts cellulose chain breaking occurring in acidic conditions (pH 3–4). The present study aims to study the kinetic of this degradation. It assesses the validity of Arrhenius law between 20 and 90°C taking advantage of the fast depolymerization of IGI impregnated papers at room temperature and using two complementary tools: DP measurements and zero-span tensile strength. The first one is sensitive enough to measure degradation at its very beginning, while the second is more appropriate for advanced stage of degradation. Similar activation energies (97± 2 kJ mol-1) were found viaDP and zero-span measurements, and reaction rates of IGI impregnated papers were 1–2 orders of magnitude aboveavailable data related to lignin-free acidic papers. These observations suggest a dominant hydrolytic mechanismthat involves directly or indirectly oxygen and iron

Alcide d'Orbigny and the Paris Foraminifera: story of a collection under Byne attack

International audienceIn 1858, the National Museum of Natural History, Paris, acquired the prestigious foraminiferal collection of the French naturalist Alcide Dessalines d’Orbigny (1802-1857). Pioneer in the fields of micropaleontology and biostratigraphy, d’Orbigny’s deep interest in tiny shells and micro-fossils led him to publish the first classification of the Phylum of Foraminifera in 1826. He later became the first professor of palaeontology at the Museum. However, quarrels in the teaching community resulted in multiple vacancies at the chair of palaeontology after d’Orbigny’s death. His collection, which includes about 800 slides of type specimens, 3D sculptures enlarged 40-200 times, hundreds of “unpublished plates” and a thousand small bottles of sediments, was progressively abandoned. For almost a century, the foraminifera have been left to the care of scientists external to the museum. In 2007, a position of professor of micropaleontology was finally created and micropaleontological collections were gathered. Until then, the conditions of conservation of this outstanding scientific resource have been relatively unknown

Un nouvel outil pour évaluer le risque de migration d'encres ferrogalliques : possibilités et limites

International audienceLes encres ferrogalliques sont sensibles à l’eau et certains traitements de restauration provoquent, autour des traits, des halos bruns, plus ou moins perceptibles, qui s’accompagnent d’une migration de fer préjudiciable à la conservation du support. Ces migrations sont difficiles à éviter car les tests de solubilité pratiqués par les restaurateurssont peu fiables.Un test colorimétrique a été récemment proposé pour évaluer les risques de migrations au cours d’un renforcementavec une colle à base d’eau. Il consiste à tester la procédure de renforcement elle-même qui doit être appliquée sur un papier portant une inscription d’encre ferrogallique et préalablement imprégné de bathophénanthroline, un réactif qui se colore en rose en présence de traces de Fe(II). L’absence de couleur rose (test négatif) permet de conclure à l’innocuité de la procédure. Ce test fonctionne bien pour évaluer l’impact des colles aqueuses et nous avons cherché à l’utiliser surd’autres types de traitement, en rapprochant au besoin les résultats obtenus avec l’examen de documents originaux.Ce test s’avère inadapté pour évaluer les traitements par immersion et les traitements à base de solvants organiques. Il permet en revanche une évaluation fiable des traitements aqueux où l’apport d’eau est modéré, sans extraction possible

Scanning Electrochemical Microscopy for the Electroless Deposition of Gold on Natural Pyrite: Effect of Ferric Ions

International audienceThe local electroless deposition of gold on pyrite is studied by scanning electrochemical microscopy (SECM). The SECM and additional SEM experiments provide kinetic and mechanistic insights on the local galvanic replacement of pyrite by gold. We evidence that individual gold nanoparticles or full coverage of gold on the pyrite surface can be obtained by controlling either the deposition time or the flux of gold ions electrogenerated at the ultramicroelectrode. We also studied the influence of ferric ions, known to be implied on gold etching and pyrite corrosion and therefore, on the overall process of gold deposition on pyrite. We then demonstrate that the presence of ferric ions significantly modifies i) the thermodynamic of the gold electro-dissolution, ii) the process of adsorption of auric ions on pyrite in the first instants, iii) the number of nucleation sites on the pyrite surface and, iv) the structure of the deposited gold layer

Byne's Decay :The Case of Alcide d’Orbigny’s Foraminiferal Collection

International audienc

Le scriptorium et la bibliothèque du Mont Saint-Michel au XIe siècle : analyse matérielle des manuscrits (parchemins, encres, pigments et liants)

International audiencePrésentation des résultats du projet Patrimoine écrit 2018-2019, co-porté et co-dirigé par Laurianne Robinet (Centre de Recherche sur la Conservation des Collections) et Stéphane Lecouteux (ville d'Avranches).La séance de trois heures (10h-13h) se déroulera ainsi :1. Le projet Patrimoine écrit 2018-2019 et ses objectifs (Laurianne Robinet & Stéphane Lecouteux)2. Démarche analytique et évolutions (Anne Michelin, Laurianne Robinet & Véronique Rouchon)[Pause (15 min.)]3. Résultats des analyses matérielles réalisées sur les manuscrits (Lucie Arberet)4. Interprétation des résultats (Stéphane Lecouteux)5. Bilan et perspectives (Laurianne Robinet & Stéphane Lecouteux