Isotope Tracers to Investigate Reactive Zones in Stones from Built Cultural Heritage

AbstractThis work aims at identifying the reactive zones inside limestone used in monuments exposed to fog. The location of these zones and the depth of the water penetration front is of primary relevance to evaluate the transport of aggressive species and the influence of environmental conditions on alteration mechanisms and kinetics of limestone exposed to the atmosphere. We report herethe results of weathering experiments conducted in a deuterium-enriched environment and the characterization of reactive zones analyzedby NanoSIMS. It was determined that water penetrated several hundred micrometers inside the limestone and that only the first micrometerswere significantly altered

The rose of the Sainte-Chapelle in Paris: sophisticated stained glasses for late medieval painters

The restoration of the rose (15th century) of the Sainte-Chapelle in Paris, France, offered a unique opportunity to investigate the color and chemical composition of these emblematic medieval French stained glasses with non-destructive analyses. The obtained results are aimed at complementing the knowledge from art historians and thus together trying to compensate for the total absence of archives on the construction of the rose. Comparison with the glasses of the nave (13th century) reveals an important evolution of the aesthetics based on new types of glasses: new colors and extensive use of flashed glass. The systematic study of the chemical composition of both sides of each glass piece revealed that about half of the studied glasses were flashed. For non-flashed glasses, this comparison allowed evaluating the influence of glass surface weathering, although very moderate, on the composition variability. In light of the variability criteria, the multivariate analysis of the chemical composition allowed inferring that most glasses originate from the same production glasshouse. The new colors result from the original composition of flashed glass, allowing superimposing otherwise incompatible redox states of the coloring transition elements. The comparison with the glasses of the nave reveals the glass technology evolution that occurred over two centuries and allowed the production of new glasses for the medieval glaziers at the eve of the Parisian Renaissance

The rose of the Sainte-Chapelle in Paris: sophisticated stained glasses for late medieval painters

The restoration of the rose (15th century) of the Sainte-Chapelle in Paris, France, offered a unique opportunity to investigate the color and chemical composition of these emblematic medieval French stained glasses with non-destructive analyses. The obtained results are aimed at complementing the knowledge from art historians and thus together trying to compensate for the total absence of archives on the construction of the rose. Comparison with the glasses of the nave (13th century) reveals an important evolution of the aesthetics based on new types of glasses: new colors and extensive use of flashed glass. The systematic study of the chemical composition of both sides of each glass piece revealed that about half of the studied glasses were flashed. For non-flashed glasses, this comparison allowed evaluating the influence of glass surface weathering, although very moderate, on the composition variability. In light of the variability criteria, the multivariate analysis of the chemical composition allowed inferring that most glasses originate from the same production glasshouse. The new colors result from the original composition of flashed glass, allowing superimposing otherwise incompatible redox states of the coloring transition elements. The comparison with the glasses of the nave reveals the glass technology evolution that occurred over two centuries and allowed the production of new glasses for the medieval glaziers at the eve of the Parisian Renaissance

Corrosion sensitive dosimeter material for environmental condition control in culture heritage

Das Ziel dieser Arbeit war es, ein neues Dosimetermaterial zu entwickeln, das schneller reagiert als der klassische Glassensor. Einen vielversprechenden Ansatz dafür bietet der Sol-Gel Prozeß, mit dem dünne Schichten hergestellt werden können. Erste Versuche mit transparenten Schichten einer glasähnlichen Zusammensetzung (mit einem hohen Anteil an K und Ca) waren nicht erfolgreich, da eine deutliche Erhöhung der Reaktivität nicht erreicht wurde. Schichten, die einen sehr hohen Ca-Anteil aufweisen, zeigten allerdings die gewünschte Empfindlichkeit gegen Umwelteinflüsse. Die neuen „Rapid-Sensoren“ werden aus einem vorkonsensierten SiO2-Sol (Silizium (IV) Oxid-Sol) und Ca(NO3)2 4H2O in Aceton (Molverhältnis Ca : Si = 10 : 1) hergestellt. Objektträger werden mit diesem Sol beidseitig beschichtet. Die Tauchbeschichtung und die Temperung (5 Minuten bei 600 °C) wurden auf hohe Empfindlichkeit gegen Feuchtigkeit und Schadgase (Screening Test in einer Klimakammer) optimiert. Die neuen Sensoren sind im sichtbaren Spektralbereich nicht transparent, sondern opak, können aber wie die klassischen Glassensoren mit IR-Spektroskopie (in Transmission) ausgewertet werden, wobei der Anstieg der OH-Bande bei 3300 cm-1 als Mass für den Korrosionsfortschritt (genannt E-Wert) dient. Die aktive Sensorschicht setzt sich aus kristallinen und amorphen Bestandteilen zusammen. Die Zusammensetzung und Morphologie der Kristallphase wurde weitestgehend charakterisiert. Mit Lichtmikroskopie lässt sich die Oberfläche des Rapid-Sensors als eine Vielzahl kleiner polygoner Kristalle charakterisieren, für die im REM beobachtet verschiedene Wachstumsstufen erkennbar sind. Mit Hilfe der EDX-Analyse und ICP-AES wurden Si, O, Ca und Na als die Hauptelemente der Schicht bestimmt. Mit SNMS-Tiefenprofil konnte eine Diffusion von Na aus dem Objektträger in die Schicht nachgewiesen werden, was zu einer besonders guten Haftung führt. Mittels Röntgendiffraktometrie, IR- und Raman-Spektroskopie lassen sich Informationen über die Struktur der Schicht erhalten: die Kristallphase besteht aus einer Mischung aus Calciumoxid und Calcium-silicat-en, die mit XRD schwer zu unterscheiden sind. Auch im infraroten Spektralbereich weisen die Si-O-Schwingungen auf silicathaltige, Bestandteile in der amorphen Schicht hin. Für die Kalibrierung des neuen Dosimetermaterials sind Bewitterungen unter kontrollierten Bedingungen grundlegend notwendig. Dazu wurde ein Bewitterunsprogramm (I) mit hoher Feuchte und Temperatur (40 °C, 98 % r.F.) sowie ein zweites mit Zugabe von SO2 als Schadgas (II) gewählt. Beide Programme beschleunigen die Umweltwirkung im Vergleich zu Realbedingungen und haben sich in anderen Versuchen mit klassischen Glassensoren bewährt. Zusammenfassend lässt sich aus den Bewitterungsversuchen feststellen, dass der neue Sensor integrativ auf Temperatur, Feuchte, und Schadgas reagiert. Entsprechend der Reaktion des klassischen Sensors führt eine Temperatur / Feuchte- Bewitterung zur Bildung von CaCO3-Kristallen, während bei Anwesenheit von SO2 bevorzugt Gipskristalle gebildet werden. Diese Parallelen lassen den Schluß auf ein vergleichbares Reaktionsprinzip zu, obwohl die Reaktion der Calciumsilicate, aus denen die Schicht besteht, nur bedingt mit der für Glas typischen Verwitterung vergleichbar ist. Mit REM kann man bei Rapid-Sensoren beobachten, dass die Reaktion am Rand der Kristalle beginnt und in die Tiefe fortschreitet, bis zur vollständigen Umsetzung (Sättigung). Die kristallinen Korrosionsprodukte breiten sich im weiteren Verlauf auch auf der amorphen Schicht aus. Der Mechanismus ist nicht reversibel und entspricht damit nicht dem für poröse SiO2-Schichten beschriebenen Alterungprozeß. Erste Sensorstudien unter natürlicher Bewitterungsbedingungen ermöglichen einen Vergleich mit klassischen Glassensoren und umreissen das künftige Einsatzspektrum. Expositionen in der ISC-Außenstelle Bronnbach und im Grünen Gewölbe in Dresden zeigen, dass die Rapid-Sensoren schneller reagieren als klassische Glassensoren (Steigerung um etwa Faktor 3). Unter moderat korrosiven Bedingungen im Innenraum sind 4 Wochen Expositionszeit günstig (mindestens 3 Monate für Glassensoren) während im Außenraum Rapid-Sensoren innerhalb von 7 Tagen ansprechen (einige Wochen für herkömmliche Glassensoren).The goal of this work was to develop a new dosimeter material, which reacts faster than the classical glass sensor. The sol-gel process offers a promising approach for the preparation of thin layers. First attempts with transparent layers with a composition similar sensitive glass (with a high concentration of K and Ca) were not successful, since a clear increase of reactivity was not reached. Layers, which exhibit a very high calcium concentration finally showed the desired sensitivity to environmental influences. The new "Rapid-Sensor" is prepared from a pre-condensed SiO2-Sol (silicon (IV) oxide Sol) and Ca(NO3)24H2O in acetone (molar ratio Ca : Si = 10 : 1). Microscopic slides are coated with this sol from both sides by dip coating. The curing process (5 minutes at 600 °C) has been optimised for high sensitivity to humidity and pollutants (screening test in a climatic chamber). The new sensors are not transparent, but opaque. Nevertheless, they can be evaluated like the classical glass sensors with IR spectroscopy (in transmission mode), whereby the increase of the OH-band at 3300 cm-1 serves as a measure for the corrosion progress (so-called E-value). The sensitive coating consists of crystalline and amorphous components. The composition and morphology of the crystal phase were characterised as far as possible. With light microscopy the surface of the Rapid-Sensor can be described as a multiplicity of small polygonal crystals, for which in the SEM different growth steps are recognisable. With EDX and ICP AES analysis, the elements Si, O, Ca were determined as the main elements of the layer. With SNMS depth profile the diffusion of Na from the support (microscopic slide) into the layer can be proven, what leads to a particularly good adhesion. By means of X-ray, IR and Raman spectroscopy information about the structure can be received: the crystal phase consists of a mixture of calcium oxides and silicates, which can not be differentiated further with XRD. In the infrared spectrum signals designated to vibrations of Si-O confirm that silicates are present in the amorphous layer. For the calibration of the new dosimeter material, weathering experiments under controlled conditions are fundamentally necessary. Therefore, an accelerated ageing program (I) with high humidity and temperature (40 °C, 98 % r.F.) as well as a second program with the addition of SO2 as pollutants (II) has been selected. Both programs accelerate the environmental effect as compared with natural conditions and have been applied in previous experiments with classical glass sensors. As a conclusion, it can be stated from the environmental testing that the new sensor integrates the impact of temperature, humidity, and pollutants. Similar to the reaction of the classical sensor weathering at high temperature and high humidity leads to the formation of CaCO3 crystals, whereas in the presence of SO2 gypsum crystals are preferably formed. These similarities permit the conclusion that a comparable reaction principle might exist, although the reaction of the calcium silicate, of which the layer consists, is not necessarily comparable with the typical glass weathering. With SEM one can observe that the reaction of Rapid-Sensors begins at the edge of the crystals and progresses into depth, up to complete conversion (saturation) has been achieved. The crystalline corrosion products spread over the amorphous layer. The mechanism is not reversible and does not correspond thereby to the ageing process described for porous coatings of SiO2. First sensor studies under natural weathering conditions make a comparison possible with classical glass sensors and outline the future spectrum of use. Exposures in Bronnbach and in the Grünen Gewölbe Museum (Green Dome) in Dresden show that the Rapid-Sensors react faster than classical glass sensors (about three times increase). Under moderately corrosive conditions indoor 4 weeks exposure time are requested (at least 3 months for glass sensors). For outdoor applications Rapid-Sensors respond favourably within 7 days (some weeks for conventional glass sensors)

Les verres de la rose de la Sainte-Chapelle de Paris ont-ils été fabriqués dans la Vôge ? Méthodes d’observation et d’analyse

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Analyses of early Medieval stained window glass from the monastery of Baume-les-Messieurs.

The collection of early medieval window glass found in the abbey of Baume-les-Messieurs (Jura, France) is exceptional because it dates to the end of the eighth century, and due to the number of fragments as well as their state of conservation. Different colours and forms have been identified. These pieces are a rare opportunity to address the glass craft, its recipes and techniques for a phase of its history that has remained little known. Analyses in PIXE–PIGE prove that, in addition to fragments from two soda glass items, the pieces are made from wood-ash glass. Most of them probably came from the same production and the raw material is present in the region. At this early stage of wood-ash glass production, the glassmakers had mastered the glass as well as the colour processe

Use of Hydrogen Isotopes to Understand Stained Glass Weathering

International audienceIn order to assess the kinetic role of the alteration layers formed on stained glass windows weathered for several centuries, aspecific experiment was designed. An ancient stained glass sample was subjected to an artificial simulated fog doped indeuterium for 13 weeks. The aim was to trace the circulation of water through the alteration layer and to locate reactive zones.Results demonstrate that the solution rapidly circulates in the alteration layer via pores and cracks, so that transport (especiallythe supply of protons at the interface between pristine and altered glass) is not rate-limiting in the alteration process. Thealteration is rather controlled by the release of glass alkalis from ion exchange with protons at an estimated diffusion rate,consistent with the long-term apparent kinetics measured on medieval stained glasses

Les vitraux du haut Moyen Âge de Baume-les-Messieurs (Jura, France) : contexte stratigraphique, analyses archéométriques et mesures conservatoires

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Les vitraux du haut Moyen Âge de Baume-les-Messieurs (Jura, France)

peer reviewed

Role of secondary phases in the scaling of stained glass windows exposed to rain

International audienceThe cyclic nature of atmospheric conditions triggers different weathering responses. Although studied in the past in solution, the complex alteration mechanisms were not adequately described. In the present work, atmospheric weathering of medieval SiO2-K2O-CaO glass was studied via field exposure of model-glasses and ancient stained glasses. Local dissolution and precipitation of secondary minerals, mainly calcite, create a fracture network, allowing water to move into the glass enhancing alteration processes and scaling of the surface. In fine, the renewal of glass surface by removal of altered scales helps accelerate the alteration rate and prevents the formation of a protective layer