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Imaging techniques, along with their subsequent processing and analysis, are of utmost importance in the visual documentation of conservation processes of cultural heritage (CH) objects. Amongst them, Reflectance Transformation Imaging (RTI) is being used as a tool for the enhancement of surface topography, such as decorative details. This paper proposes a new approach based on advanced RTI data processing and analysis to document the condition of metal artefacts or monitor their conservation treatments. First, the methodology for mapping geometric and statistical information from the stack of RTI image data and their relation to the surface topography and the appearance attributes resulting in feature maps is described. Additionally, the possibility of quantifying intra- or inter-surface changes based on saliency and distance measurements by applying the Mahalanobis distance (MD) on feature maps is demonstrated. This methodology is then used for documenting the condition and monitoring the cleaning treatment of a late Roman coin.

La réalité augmentée est actuellement testée au château de Germolles (Saône-et-Loire) – demeure de plaisance de la duchesse de Bourgogne Marguerite de Flandre, épouse de Philippe le Hardi –, afin de retranscrire auprès du grand public les dernières recherches menées sur les peintures murales médiévales redécouvertes dans les années 1970 et en partie restaurées en 1989-1995. Celles-ci ont bénéficié d’un travail de re-documentation conduit avec le soutien technique et financier de l’Action européenne COST COSCH (COlour and Space in Cultural Heritage) et de la direction régionale des Affaires culturelles de Bourgogne - Franche-Comté. Il a permis de déterminer le niveau d’authenticité des peintures, de caractériser les décors présentant des traces de tôles d’étain doré rehaussées de repeints et d’évaluer leur état de conservation. Cet article reprend les résultats obtenus avant de préciser les conditions de mise en place de l’expérience de réalité augmentée. Les difficultés rencontrées sont décrites, comme les solutions techniques apportées. L’application étant d’ores et déjà intégrée au parcours de visite, un premier retour d’expérience des visiteurs du château est présenté, et quelques perspectives sont discutées. Augmented reality is currently being tested at château de Germolles- the residential palace of Duchess of Burgundy Margaret of Flanders, wife of Philip the Bold- to help the general public visualise the outcomes of the latest researches on the medieval mural paintings that were rediscovered in the 1970s and partly restored in 1989-1995. The mural decorations have been re-documented with the technical and financial support of the EU COST Action COSCH (COlour and Space in Cultural Heritage) and The Regional Directorate of Cultural Affairs of Burgundy - Franche-Comté. It helped determine the level of authenticity of the paintings, characterise the decors that featured traces of gilded tinfoil covered with glaze or paint and evaluate their state of conservation. This article summarises the results obtained and then focuses on the conditions of the augmented reality experience setup. The difficulties encountered are described as well as the technical solutions that were provided. The application has already been integrated into the guided tours of the château, thus allowing a first feedback from the visitors. Future perspectives are also discussed.

The absolute dating of paintings is crucial for tackling the problem of fake art. Investigations to authenticate paintings rely on an advanced knowledge of art history and a collection of scientific techniques. Radiocarbon dating is the only technique that gives access to an absolute time scale, but its application is limited to organic materials such as wood, canvas or natural binder. Extending absolute dating to inorganic pigments would make it possible to overcome the lack of available materials for dating easel and mural paintings. Here, we present a novel technique permitting paintings that contain inorganic pigment to be radiocarbon dated. We report results obtained on lead white that was the major white pigment used from Antiquity to the 20th century. We demonstrate that its manufacture is the key point for an absolute and reliable dating. We report an unprecedented use of 14C to date 14th to 16th century wall paintings. Since lead white was extensively used by the greatest artists, we anticipate that this study will open new avenues for detecting forgeries on the art market and for museums.

Imaging techniques were used to document and monitor physical damage to the unique wall paintings at the Château de Germolles, Burgundy, France. Photogrammetry combined with scanning are the most appropriate techniques to monitor the evolution of microcrack networks in the cornice overhanging the paintings and preserved as a witness to 19th century additions.

The absolute dating of paintings is crucial for tackling the problem of fake art. Investigations to authenticate paintings rely on an advanced knowledge of art history and a collection of scientific techniques. Radiocarbon dating is the only technique that gives access to an absolute time scale, but its application is limited to organic materials such as wood, canvas or natural binder. Extending absolute dating to inorganic pigments would make it possible to overcome the lack of available materials for dating easel and mural paintings. Here, we present a novel technique permitting paintings that contain inorganic pigment to be radiocarbon dated. We report results obtained on lead white that was the major white pigment used from Antiquity to the 20th century. We demonstrate that its manufacture is the key point for an absolute and reliable dating. We report an unprecedented use of 14C to date 14th to 16th century wall paintings. Since lead white was extensively used by the greatest artists, we anticipate that this study will open new avenues for detecting forgeries on the art market and for museums.

International audience; The aim of this study was to examine and document the wall paintings in theChâteau de Germolles. Situated in Burgundy, France, Germolles is the best preservedresidence of the Dukes of Burgundy and was listed as a monument ofnational importance in 1989.The medieval wall decoration of the Château de Germolles was rediscoveredunder the nineteenth-century plasters during World War II. Medieval accounts ofthe château provide a detailed list of the materials acquired to make the muraldecoration, but this list is incongruous when compared with the current appearanceof the paintings. The discrepancy between the archival and material evidence,and also the need to understand the complexity of the painting technique usedwere the main motivations for undertaking the case study described in this chapter.Imaging alongside more traditional examination techniques were utilized torecord and document the mural decoration. The objectives of the case study wereto distinguish the original materials from those applied during restoration, identifythose materials, and correlate them with the archives. We also tried to understandthe medieval painting techniques used and assess the condition of the paintingsand stabilization requirements. Finally we aimed to find a sustainable solution forthe management of the various types of data collected. Various techniques andinvestigations offered valuable insights into the materials and the painting techniqueused. To improve visitor experience, based on the information gained in thecourse of this study, a 3D virtual representation of the original decoration is currentlyproposed for display to the public visiting the Château de Germolles.

Study of the minor and trace element contents in the composition of early aluminium is interesting from a cultural history perspective because it can provide information on the evolution of aluminium smelting practice. A range of aluminium artefacts from the Swiss National Museum and the Lausanne Historical Museum, Switzerland, have been characterised with regard to their minor and trace element composition. This was performed using external beam Particle Induced X-ray Emission (PIXE) with 1 MeV protons and a portable X-ray fluorescence system. The concentration of Mn and Pb was significantly higher for artefacts produced by the amalgam process which confirms studies reported by others.

International audience

The prototyping of a newly designed electrolytic pencil for the local cleaning of silver tarnish on artifacts comprising inseparable organic components is described. The pencil helps determine the type and amount of tarnish, define the cleaning parameters (treatment potential and duration), and provides a safe and efficient way to locally and electrolytically reduce silver tarnish. The electrolyte is conveyed to and from the surface of metal objects via a micro-porous foam and is continuously renewed by two pumps. This user-friendly and ergonomic pencil is distributed as an open source kit for self-assembly with parts fabricated using innovative and low-cost technologies. The operating modes for the pencil are described. To evaluate this new tool, the pencil was used to clean a selection of tarnished silver components from composite masterpieces in the Treasury of Saint-Maurice Abbey.

La pulitura di filati, realizzati avvolgendo fibre naturali con laminette metalliche, costituenti i tessuti antichi è una problematica ricorrente nella conservazione di questi manufatti. In particolare, la difficoltà di rimuovere i prodotti di corrosione senza alterare sia la struttura della lamina metallica che le altre fibre tessili presenti, porta a cercare metodi di restauro innovativi e selettivi per preservare l'integrità dell'opera. Lo scopo di questo lavoro è quello di valutare due metodi di pulitura, ancora poco applicati in questo specifico settore, come possibili tecniche da considerare da parte dei conservatori-restauratori di tessuti. Un piviale in velluto di manifattura fiorentina del XV sec., proveniente dal Musée des Tissus di Lione (Francia), e attualmente in restauro presso l'Accademia di Francia a Villa Medici (Roma), è stato l'oggetto di questa sperimentazione. I filati metallici del cappuccio e dello stolone del piviale presentano una diversa composizione chimica e differenti problematiche di degrado dovute sia alle tecniche di realizzazione che ai fattori ambientali e/o intrinseci del materiale stesso. Il primo metodo di pulitura testato è stato realizzato con la Pleco©, una penna elettrolitica, messa a punto per l'utilizzo su superfici metalliche piccole e grandi associate a materiali organici che non dovrebbero entrare in contatto con soluzioni acquose. Nel corso della sperimentazione sono stati modificati diversi parametri per la sua applicazione su fili metallici sottili. Il secondo metodo di pulitura utilizzato è stato il laser a stato solido, il cui utilizzo nel restauro dei tessuti è ancora poco comune in Francia. Sono stati testati due tipi di laser a Nd:YAG: il primo, in modalità dell'impulso a Q-Switch (8 ns) nelle differenti lunghezze d'onda di 1064 e 532 nm; il secondo, in modalità dell'impulso a Long Q-Switch (120 ns) nella lunghezza d'onda fondamentale di 1064 nm. Per poter rispondere all'esigenza di conservare questo prezioso piviale contenente filati metallici, è stato effettuato uno studio interdisciplinare del manufatto e delle sue forme di degrado al fine di applicare e valutare i due diversi metodi di pulitura. Per quest'ultimo scopo i filati metallici del piviale sono stati analizzati mediante microscopia ottica (MO) e microscopia elettronica a scansione accoppiata alla microanalisi a raggi X a dispersione di energia (SEM-EDS), prima e dopo le operazioni di pulitura. Quest'ultima tecnica è stata selezionata come idonea all'osservazione e all' identificazione dello stato di degrado della lamina metallica che presenta una modificazione della struttura cristallina dovuta al passare del tempo, alla valutazione degli elementi chimici presenti nei prodotti di corrosione nonché alla valutazione della loro presenza/assenza dopo le operazioni di pulitura. I risultati preliminari mettono in evidenza l'efficacia di entrambi i metodi per la specifica problematica, aprendo nuove prospettive metodologiche ai responsabili della conservazione dei manufatti tessili.

[EN] The Château de Germolles is one of the rare palace in France dating from the 14th century. The noble floor is decorated with wall paintings that are a unique example of courtly love spirit that infused the princely courts of the time. After being concealed sometime in the 19th century, the paintings were rediscovered and uncovered in the middle of the 20th century and partly restored at the end of the 1990s. No scientific documentation accompanied these interventions and important questions, such as the level of authenticity of the mural decorations and the original painting technique(s) used in the medieval times remained unanswered. The combined scientific and financial supports of COSCH Cost Action and DRAC-Burgundy enabled to study Germolles’ wall paintings using some of the most innovative imaging and analytical techniques and to address some of the questions raised. The study provided significant information on the material used in the medieval times and on the conservation condition of the paintings. The data collected is vast and varied and exposed the owners of the property to the challenges of data management., [ES] El castillo de Germolles es uno de los raros palacios principescos en Francia que data del siglo XIV. La planta noble está decorada con pinturas murales que son un ejemplo único del amor cortés, ese espíritu que se divulgó en las cortes de la época.Ocultadas desde el fin del siglo XIX, las pinturas fueron descubiertas en la mitad del siglo XXy fueron parcialmente restauradas al finalde la década de 1990. No hay documentación científica queacompañelas intervenciones, y cuestiones importantesse quedaronsin repuesta, en particular el nivel de autenticidad de las decoraciones de las paredes, así como lastécnicaspictóricasutilizadasen laépoca medieval. El apoyo científico y económico de la Acción Cost COSCH y de la DRAC de Borgoña permitió elestudio delas pinturas murales de Germolles con algunas de las técnicas de imagen y analíticasmás innovadoras, con tal de responder a algunas de las cuestiones planteadas. El estudio proporcionó informaciónrelevante en lo que se refiere al material utilizado durante la Edad Mediay sobreel estado de conservación de las pinturas. La toma de datos es ampliay variada, y expuso a los dueños de la propiedad al desafío de la gestión de datos., This project would not have been possible without the financial support by DRAC-Burgundy and the COST Action TD1201: Colour and Space in Cultural Heritage (COSCH) (www.cosch.info) which the authors wish to sincerely thank.

Metal diagnosis of heritage objects is a difficult task performed by conservators, mainly due to the fact that invasive techniques are not allowed on these artifacts. Therefore, conservators have developed diagnosis methods based on the observation of the corrosion forms of the objects. However, although these methods are useful to share a common representation of one specific object, they are very difficult to use to compare or search for objects presenting similar corrosion forms. To support the comparison of different objects, we propose a new support system built upon these methods. This paper presents an innovative way to use C-K theory in order to build an artifact in an interdisciplinary context. The resulting artifact integrates concepts and knowledge borrowed from both the conservation-restoration and the information systems fields.

New protection systems for cultural heritage artefacts can be tested and their efficiency, compared to traditional systems, assessed using artificial metal coupons. The manufacturing of these coupons requires though a thorough investigation of the artefacts that they are supposed to simulate. Not only their composition, but their surface preparation (through artificial or natural aging) should copy as closely as possible real artefacts. Protection systems tested should be applied according to standardised protocols, while short term testing in humid chamber and long term testing on site should be monitored regularly to detect any possible failure. Only then the use of such artificial metal coupons will be validated. This approach is illustrated in this paper through the EU PROMET and Swiss POINT research projects.

Colour and Space in Cultural Heritage ( www.COSCH.info ) is a transdomain European Action (TD1201) in the area of Materials, Physics and Nanosciences (MPNS). The Action runs from 2013 to 2017 and benefits from the support of the European Cooperation in Science and Technology http://www.cost.eu/domains_actions/mpns/Actions/TD1201 . The Authors are active participants of the COSCH network. They represent different disciplines involved in documentation and conservation of material cultural heritage. COSCH aims to enhance applications of optical measuring techniques and electronic imaging in this area. The paper outlines scientific, theoretical and practical solutions promoted by COSCH. COSCH activities have been organised around six main subjects: (1) spectral object documentation; (2) spatial object documentation; (3) algorithms and procedures; (4) analysis and restoration of cultural heritage surfaces and objects; (5) visualisation of cultural heritage objects and its dissemination; and (6) the semantic development of the COSCH Knowledge Representation. The Authors indicate future work that is needed to resolve the identified scientific, technical and semantic questions, as well as challenges of interdisciplinary communication, to ensure a wider adoption of specialist technologies and enhanced standards in 3D documentation of material cultural heritage — being a basis for its understanding, conservation, restoration, long-term preservation, study, presentation and wide dissemination.

The focus of this study consists of examining how corrosion potential measurements can contribute in providing information on the effectiveness of storage and stabilization treatments of copper alloys in aqueous solutions. We report on the electrochemical behavior of artificial copper alloy coupons (covered or not with corrosion layers), simulating the behavior of real artifacts, immersed in sodium sesquicarbonate solutions. Particular attention is given to the transformation of the corrosion layer as a function of time. In addition, synchrotron radiation X-ray diffraction measurements are performed before and after the treatment in order to understand the reactions that take place during the immersion processes.

The paper introduces some key interdisciplinary questions concerning the development of optical measuring techniques and electronic imaging applied to documentation and presentation of artefacts, as identified through the work of Colour and Space in Cultural Heritage (www.COSCH.info), a trans-domain European Action (TD1201) in the area of Materials, Physics and Nanosciences (MPNS) supported, since 2013, by the European Cooperation in Science and Technology http://www.cost.eu/domains_actions/mpns/Actions/ TD1201. Some 125 international researchers and professionals participate in COSCH activities which have been organised around six main subjects: (1) spectral object documentation; (2) spatial object documentation; (3) algorithms and procedures; (4) analysis and restoration of cultural heritage surfaces and objects; (5) visualisation of cultural heritage objects and its dissemination; and (6) the semantic development of the COSCH Knowledge Representation.

Colson Isabelle, Degrigny Christian, Dubus Michel. Les chartes scellées par des bulles de plomb et leur conservation aux Archives nationales. In: La Gazette des archives, n°192, 2001. pp. 221-238.

Treatment of waterlogged iron and iron-wood artifacts using PEG 400 solutions with and without Hostacor IT was monitored to determine if the inhibitor is effective long-term in stabilizing iron embedded in wood. Corrosion potentials of iron were taken on a daily basis for around two months and were compared to potentiodynamic measurements conducted for iron under the same treatment conditions. The pH, chloride and bioactivity contents of the solutions were also measured. The results show that Hostacor IT is effective in slowing down the corrosion of exposed iron in PEG 400 solutions. However, the corrosion potentials for iron embedded in wood in PEG 400 with Hostacor IT do not suggest passivation by the inhibitor. Also, the bioactivity contents were much higher for PEG 400 solutions with Hostacor IT than without. During treatment, biofilms surrounded iron nails in PEG 400 solution with or without Hostacor IT but were found not to affect the passivation of iron by Hostacor IT. Finally, this study d...

Electrochemical methods, including polarization experiments and impedance spectroscopy, were used to evaluate the eAectiveness of benzotriazole (BTA) in an aqueous solution of polyethylene glycol (PEG) in protecting polished archaeological copper or archaeological copper covered with corrosion products. The adsorption of PEG on the polished copper significantly limited the corrosion current. The presence of benzotriazole enhanced the protection of the polished copper, giving maximum protection at a concentration of 10 ˇ2 mol l ˇ1 of BTA in 20 vol % PEG 400 solution. On the other hand, PEG solutions caused degradation of the corrosion products of the copper. This degradation increased with time. When BTA was added, the corrosion products were preserved and, the higher the BTA concentration, the more the corrosion current decreased. In PEG 400 solution protection of the corrosion products of the copper by BTA improved over time.

The corrosion inhibitor Hostacor KS1 is used in polyethylene glycol (PEG) solutions to treat waterlogged iron-wood composite artifacts, but the manufacturer has now replaced this product by Hostacor IT. An electrochemical study compares the behaviour of Hostacor KS1 and Hostacor IT in various concentrations and grades of PEG solution. The corrosion potential was measured versus time, and cathodic and anodic polarization experiments were conducted for polished archaeological wrought iron (without corrosion products) in PEG solutions with and without inhibitor(s). The results reveal that both Hostacor KS1 and Hostacor IT spontaneously passivate iron in PEG solutions, by acting as anodic inhibitors that react with dissolved oxygen in the solution, and so prevent the corrosion of iron. The similarity of the electrochemical test results indicates that Hostacor IT is a suitable replacement for Hostacor KS1.

Examination of the painted metal parts of a Citroen catelpillar car known as ‘Le Croissant d'Argent’, which took part in the Sahara Crossing of 1922–23, revealed that despite widespread corrosion the original paintwork had survived. A procedure was devised to clean and stabilize the painted metal surfaces, using pads soaked in a complexing solution of the tetrasodium salt of edta to dissolve surface corrosion products, and stabilizing oxidized iron alloys with an alcoholic acid mixture. This method is offered as a useful alternative for those responsible for automobile collections when minimal intervention is judged sufficient. The tests carried out to develop the treatments are also described.

International audience; Recent developments in laser techniques in the conservation field have allowed us to test the laser cleaning of tarnished silver and copper threads in textiles. The experimental samples were copper and silver plates that had been artificially sulphurised as well as silk bands dyed according to traditional procedures. The experiments were carried out with different Nd3+:YAG lasers emitting infrared, visible and ultraviolet radiation. The work has focused on optimising the cleaning process to control the side effects (whitening or yellowing of silver and reddening of copper) produced. Tests were also conducted on real artefacts, and the results are discussed.

International audience; The properties of water–polyethylene glycol (PEG 400) solutions vary with the PEG content. The highest acidity and conductivity values were observed in 20% PEG 400 solutions. Oxygen solubility in such solutions decreased as the PEG 400 content increased. Adsorption of PEG 400, estimated by EQCM, varied with the PEG 400 concentration, also reaching a maximum in 20% PEG 400 solutions, with the weight of the adsorbed layer reaching 3.5 μg cm−2.Iron corrosion in water–PEG 400 solutions was studied by monitoring the corrosion potential and the polarization curves. Iron corrosion was highest in the 20% PEG 400 solution due to the compromise between the evolution of acidity, dissolved oxygen content and the adsorption and complexation properties of the PEG solutions. Through adaptation of the Bockris mechanism, PEG adsorption at the metal surface constituted the first stage in the iron corrosion mechanism. Iron (ions)/PEG complexes were then formed, which diffused in solution.

Treatment to stabilize aluminium alloys deriving from submerged aeronautic remains by cathodic polarization in sodium citrate solution extends to the associated composite systems comprising iron alloys. Due to galvanic corrosion, the steel is covered with a thin layer of corrosion which must be eliminated without damaging the aluminium alloys in contact with it. It is therefore proposed to add to the usual treatment by chemical and electrolytic methods a new corrosion-removal step for the ferrous parts, using a corrosion-inhibiting solution for aluminium alloys. The conditions for treatment—solution concentration, cathodic potential applied, the need for good agitation—are described in the case of a BMW 801 D2 engine from a Focke-Wulf 190 plane which was submerged for 45 years in the river Le Loiret.

International audience

The electrochemical stabilization of archaeological cast iron, currently used in restoration and conservation, is designed to extract chlorides by applying an electrical field between the metal (object containing a metal core), which is cathodically polarized, and a stainless steel cage, which is anodically polarized. However, stabilization of artifacts in potentiostatic mode is a relatively long procedure and weakens the artifacts because of the hydrogen evolution when the applied voltage is too negative. In an effort to reduce the secondary effects caused by hydrogen, we decided to study the use of pulsating currents. The aim is to be selective with respect to the reactions produced and to increase the rate of dechlorination treatment. By applying a pulsating signal with a constant current and a limit potential (Elim, Elim

International audience

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