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Indoor air quality on board a 36-year-old ship has been characterized at several locations. The ship is dedicated to nearshore operations at the Belgian coast. This paper presents time-averaged and continuous-time measurements of several indoor pollutant concentrations such as NO2, O3, NO, CO, total volatile organic compounds (TVOC), polycyclic aromatic hydrocarbons (PAH), particulate matter PM2.5 and PM10, black carbon, and individual organic compounds. Time-averaged measurements suggest that the ship’s indoor air quality is sufficiently safe according to the prescribed occupational and nonoccupational health limits. However, the concentration of some indoor pollutants is comparable to that of the outdoor air of a large city such as Brussels, Belgium. Continuous-time analyses show that the temporal trends of indoor pollutant concentrations are inherently unstable. A large number of peaks or valleys are observed on a slowly fluctuating background. At some occasions, pollutant concentrations exceed the nonoccupational thresholds. Several pollutant peaks occur simultaneously, resulting in a pattern of peaks that is typical for a pollution source (e.g., exhaust gases entering the ship’s castle through the ventilation inlet, human presence, and bunkering). This study illustrates that multiparameter monitoring campaigns give valuable information about the behaviour of pollution sources, facilitating the definition of mitigation actions.

The relationship between bibliographic and archival research, on the one hand, and object-based study, on the other, forms a very important basis for research into historical production techniques. Several written sources provide insight into the recipes for dyeing black in the past. Yet, this does not guarantee that these written recipes are representative of an entire society or were used in the dyers practice. The way to assess how closely practical dyeing and written sources are aligned entail the chemical analysis of historical textiles. This article focuses on the identification of the ingredients used to dye wool black in the case of well-preserved and dated (1650-1850) historical textiles from five Belgian archives and some remaining historical artefacts. The results are compared with the technical knowledge of dyeing and the ingredients mentioned in written sources from the same period. The aim is to refine the knowledge of the different black dye ingredients used in practice in Northwest Europe during the period. Received: 2018-6-17Revised: 2018-12-20Accepted: 2019-1-4Online: 2019-3-10Publication: 2019-4-30, A relação entre a investigação bibliográfica e arquivística e a investigação baseada em objectos históricos constitui um ponto de partida fundamental para o estudo de antigas técnicas de produção. Várias fontes documentais dão uma imagem de como se tingia de preto no passado. Contudo, nada garante que estas receitas sejam representativas de uma sociedade no seu todo ou que fossem praticadas pelos próprios tintureiros. A análise química de têxteis históricos constitui um método eficaz para verificar a proximidade entre práticas de tingimento e fontes documentais. Este artigo foca-se na identificação dos ingredientes usados no tingimento de lã com cor preta num conjunto de têxteis históricos datados (1650-1850) e em excelente estado de conservação de cinco arquivos belgas e noutros objectos históricos. Os resultados são comparados com o saber tecnológico associado aos métodos de tingimento e aos ingredientes descritos segundo as fontes documentais da época. O objectivo é o de afinar o conhecimento sobre os ingredientes usados no tingimento de preto no noroeste da Europa durante o período em questão. Recebido: 2018-6-17Revisto: 2018-12-20Aceite: 2019-1-4Online: 2019-3-10Publicação: 2019-4-30

The data presented in this article are related to the measure- ments in the contribution titled: ‘Tarnished silver-copper sur- faces reduction using remote helium plasma at atmospheric pressure studied by means of high-resolution synchrotron x-ray photoelectron microscopy’ published in Corrosion Sci- ence. X-ray photoelectron spectra were collected from pure silver, sterling silver (92.5 w% Ag and 7.5 w% Cu) alloy and pure copper. These metals were artificially sulphidised. A remote helium plasma at atmospheric pressure was applied on the metallic and sulphidised state. Then the top layer of the 4 surface states were analysed at the NanoESCA beamline (Electron Spectroscopy for Chemical Analysis at the Nanoscale) at Elettra Sincrotrone Trieste. The instrument installed as an end station at the NanoESCA beamline of the Elettra storage ring combines an electrostatic Photo Electron Emission Microscope (PEEM) with a double-hemispherical (‘IDEA’) analyser, allowing the collection of photoemission electron microscopy (PEEM) images, X-ray photo electron- energy-filtered images and XPS spectra. The NanoESCA beamline provides electromagnetic radiation with variable polarization (linear, circular) and energies up to 10 0 0 eV. Information for Cu3p, Cl2p, S2p, C1s and Ag3d were obtained by collecting spectra at 450 eV. The goal of the analyses was to determine how the plasma treatment changed the top layer of the metallic and sulphidised surface of pure silver, sterling silver and pure copper. This contribution focuses on the calibration of the collected XPS spectra, as well as the impact of the plasma treatment on the surface states.

Previous investigations suggested that sulphide layers on pure silver surfaces were easily removed with a reducing plasma afterglow at atmospheric pressure, but were harder to remove on silver-copper alloys. In this study we investigated by synchrotron x-ray photoelectron spectroscopy the effect of plasma afterglow on tarnished pure silver, pure copper and sterling silver alloy. The results confirmed that plasma was able to reduce in depth all sulphides except Cu2S. The process was explained by standard reduction potentials and allowed to draw a detailed picture of the submicrometric evolution of the tarnished layers.

Organizations collect an ever-increasing amount of data concerning environmental parameters. Non-experts may be confronted with an information overload, making the data meaningless. A way to circumvent this problem is visualizing the trends in the pollution concentrations measured over time. However, non-experts do not have a mental model to derive air quality information from displayed concentration profiles. Therefore, a large fraction of the stakeholders remains unable to read/interpret such data effectively. To improve communication with stakeholders, we superposed health risk information from 9 different Air Quality Indices (AQIs) on different kinds of graphs. The visualization methods are applied on data collected by the Belgian Environment Agency from two monitoring stations located in contrasting regions, Ghent and Vielsalm. Supplementary, spatially distributed pollution is shown using data collected from Sentinel-5p satellite. Despite some limitations of the AQIs, the applied visualizations methods successfully translate the data obtained into actionable information.

This study demonstrates that the mechanism responsible for the transformation of glass into a degradation layer is pH-dependent. In acid conditions, the transformed glass is homogeneous and brittle. In mild alkaline conditions, transformed glass is heterogeneous due to the presence of lamellae composed of silica nanoparticles and the occurrence of Ca-rich inclusions. The fundamental difference between acid and alkaline conditions cannot be explained by the currently accepted degradation mechanism based on ion exchange. To explain this critical observation, we propose a refined degradation mechanism based on existing knowledge that involves several inwardly moving reaction fronts. The fronts responsible for the transformation of the silicate network into amorphous silica are also responsible for the morphology of the transformed glass. We have identified the feedback mechanism that explains the formation of lamellae in alkaline conditions.

In many situations or applications, it is essential to evaluate the air quality in relation to human health. For that reason, a monitoring system has been designed with the objective of accurately measuring temporal trends in the air mixture that we breathe. Parameters such as temperature, relative humidity, several inorganic gases (CO2, O3, SO2, CO), the total volatile organic compounds (TVOC) and the concentration of particulate matter need to be measured simultaneously in order to achieve an operational sensing node. With current technology, it is possible to use open-source hardware and software to create a low-cost monitoring system. At present, the development and selection of the hardware, software platforms and the sensors associated with these applications, constitute a scientific and technological interest. The possibility of creating compact, economically accessible systems, based on open-source hardware and software, increases the possibility to perform such analyses at a larger scale and by simple citizens. The proposed system is a prototype in the initial phase, so only the operational capabilities of the system were evaluated during periods of time of 24 and 72 hours of continuous operation, the response of the sensors to step-type inputs and the measurement of background concentrations in urban interior environments.

Within the heritage field, the application of strain gauges on wood surfaces is a little-explored but inexpensive and effective method to analyse the environmental appropriateness of rooms for the wooden heritage collections they contain. This contribution proposes a wood sensor connected to a data logger to identify short moments with an elevated risk of harm. Two experiments were performed to obtain insights pertaining to the applicability of wood sensors to evaluate preservation conditions. (1) The representativeness of strain gauges on dummies was tested for their use in evaluating the preservation conditions of a range of wooden objects exposed to the same environment. For this, three situations were mimicked: a bare wood surface, a wood surface covered with a preparation layer, and a wood surface covered with a preparation and varnish layer. (2) The usability of strain gauges to monitor the wood behaviour in real-time measurements was tested with a monitoring campaign of almost two years in a church where a new heating system was installed. The results of both experiments are promising, and the authors encourage a broader application of strain gauges in the heritage field.

It is commonly known that the conservation state of works of arts exhibited inside museums is strongly influenced by the indoor environmental quality (IEQ). Heritage institutions traditionally record and evaluate their IEQ by monitoring temperature, relative humidity, and -more rarely-light. However, smart use of technology enables monitoring other parameters that give a more complete insight in environmental ‘air aggressiveness’. One of this parameters is particulate matter (PM) and especially its concentration, size distribution and chemical composition. In this work, we present a selection of data sets which were obtained in a measuring campaign performed in the War Heritage Institute in Brussels, Belgium. A continuous monitoring of PM concentration with a light scattering based particle counter was performed. In addition the daily mass concentration and size distribution of airborne PM was monitored by means of Harvard impactors. The chemical composition of sampled PM was inferred from the results of XRF and IC analysis. The insights from these datasets are combined with the results of traditional environmental monitoring (temperature, relative humidity and light intensity), and assessed against the recommended guidelines for conservation environments. By using an integrated approach based on the calculation of an IEQ-index, we present a straightforward methodology to evaluate and visualize the IEQ including also continuous PM monitoring. It is clear from the results of this study how including PM in IEQ analysis allows to identify potential risks for museum collections that remain invisible when only traditional parameters are considered.

A plasma afterglow from a gas mixture of 5 vol% H2 in He is able to remove tarnish layers on pure silver in a matter of seconds. This dry, localized, and noncontact cleaning technique is a promising method to clean historical objects where silver is combined with organic materials and where traditional cleaning techniques are not recommended. However, historical objects are often manufactured with silver alloys but somehow their tarnish layers are removed less effectively with plasma treatments. To understand the different impact of the afterglow, the surfaces of corroded silver, sterling silver, and copper coupons are characterized before and after plasma treatment by a multianalytical approach combing optical and confocal microscopy, scanning electron microscopy coupled to energy dispersive X-ray analysis and chronopotentiometry. The analyses demonstrate that the few hundred nanometre-thick tarnish layer on pure silver is transformed through the whole thickness resulting in a porous metallic film. On top of that metallic film, some isolated remnant Ag2S particles are found. For sterling silver, a yellowing of the surface occurs. The Ag-rich corrosion products are reduced to a large extent, while the Cu-rich corrosion products are only partially reduced. For corroded copper, no apparent visual change is observed at a macroscopic scale, although the morphology of the surface changed. The results allow an evaluation of the cleaning efficiency and provide a deeper understanding of hydrogen plasma effects on the transformation of sulphide corrosion layers at atmospheric pressure.

UID/HIS/04209/2013 This work reports the first systematic chemical characterization of Portuguese 18th century glassware. 28 selected glass fragments, recovered from an archaeological excavation carried out in the site where King D. João V of Portugal established an important glass manufacture, Real Fábrica de Vidros de Coina (Coina Royal Glass Factory), were studied. This factory operated from 1719 until 1747, the year in which the factory was transferred to Marinha Grande. The fragments were analysed by micro-energy dispersive X-ray fluorescence (micro-EDXRF), using a portable spectrometer ArtTAX, and scanning electron microscopy (SEM-EDX). The analytical data showed that a large variety of glass types was manufactured in that factory, namely soda-lime glass, mixed-alkali glass, high lime-low alkali glass, potash glass and lead glass. In general, the composition of the glass varies according to the function of the objects. It was demonstrated that micro-EDXRF can be an important tool to characterize museum glass objects when only in situ non-invasive analytical methods are allowed. authorsversion published

The painting Saint Jerome, part of the collection of the Maagdenhuis Museum (Antwerp, Belgium), is attributed to the young Anthony van Dyck (1613–1621) with reservations. The painting displays remarkable compositional and iconographic similarities with two early Van Dyck works (1618–1620) now in Museum Boijmans van Beuningen (Rotterdam) and Nationalmuseum (Stockholm). Despite these similarities, previous art historical research did not result in a clear attribution to this master. In this study, the work’s authenticity as a young Van Dyck painting was assessed from a technical perspective by employing a twofold approach. First, technical information on Van Dyck’s materials and techniques, here identified as his fingerprint, were defined based on a literature review. Second, the materials and techniques of the questioned Saint Jerome painting were characterized by using complementary imaging techniques: infrared reflectography, X-ray radiography and macro X-ray fluorescence scanning. The insights from this non-invasive research were supplemented with analysis of a limited number of cross-sections by means of field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The results demonstrated that the questioned painting’s materials and techniques deviate from Van Dyck’s fingerprint, thus making the authorship of this master very unlikely.

We present a decision-support system that guides heritage guardians in selecting mitigation actions to improve the indoor air quality and thus the preservation conditions of indoor collections in heritage buildings. This contribution shows that it is feasible to build a decision support system dedicated to preventive conservation when the following barriers are overcome: 1) simultaneous measurement of a wide range of environmental parameters in order to detect a larger number of undesired situations; 2) development of an algorithm to perform reproducible indoor air quality assessments; and 3) transformation of the air quality assessment into a graph that can be read intuitively without causing a wide variation of interpretations among stakeholders. An important aspect of the decision support system is that it reduces several sources of uncertainty that hamper reliable indoor air quality assessments. The possibilities of such a system are illustrated with a measurement campaign in a church where a heating system has been installed and used for the first time.

Environmental parameters such as temperature, relative humidity, visible light, UV radiation and pollution influence the deterioration rate of heritage items. To judge on the environmental appropriateness for heritage conservation, it is therefore important to monitor the environment. Often, an incomplete set of environmental parameters is measured, or sporadic or time-averaged measurements are performed. As a result, a wide range of undesirable situations and hazards remain unnoticed. This might lead to an underestimation of environmental dangers (i.e., inaccurate judgement) or to inappropriate mitigation measures (i.e., inaccurate decision making). We present an innovative and user-friendly monitoring device that simultaneously and continuously measures (1) environmental parameters and (2) material behavior. An extended combination of off-the-shelf sensors for temperature, relative humidity, air speed, CO2, NO2, O-3 and particulate matter are connected to a multipurpose datalogger. In-house developed sensors for the shrinkage and expansion behavior of wood, as well as sensors for metal corrosion rates are connected to the same datalogger. Such extended monitoring shows the identification of a wider range of undesirable situations, and it facilitates the search for correlations between such situations and the sources that cause them, i.e., the hazards.

The exposure of cultural heritage to the environment has a significant impact on its degradation process and degradation rate. Consequently, managing the indoor air quality is vital to minimize further damage to historical artefacts and works of art. Despite its potential impact, the traditional assessment of the indoor air quality still represents a challenge for most collection guardians. This approach typically relays on the comparison of measured environmental parameters and corresponding acceptable values. However, determining the acceptable values and relative importance of the different environmental parameters turns out to be quite complex since it depends on the material types present in the collection and their preservation state. Furthermore, the significant amount of data generated during the measurements hampers the application of traditional methods of analysis. Considering all these, we propose the use of data mining as an alternative method for the indoor air quality assessment in cultural heritage studies. Data mining can provide knowledge from vast volumes of heterogeneous data, through high-speed processing, detection, and analysis. Here we present its application to identify dynamics and patterns affecting the indoor air quality in a realistic case. Using data from a measuring campaign held at a late Gothic church in Belgium, we show that inappropriate periods can be identified without using standards. In addition, different types of periods can be identified by studying the relation between multiple parameters. For that we use the k-means clustering method, interpreting the results with both visual and statistical tools.

Transmission radiography is an excellent and easy to use method to visualize the internal structure and spatial distribution of heavy Z pigments in the paint layer of 15th to 17th-century panel paintings. It is used to examine the creation process of the artist (e.g. changes in composition, underlying paintings, etc.), to identify older restorations and to solve authentication problems. However, some historical paintings have white lead-based preparatory layers. As a result, the pictorial layer can hardly be visualized in the radiographic images. This problem becomes even more important for 19th and 20th-century paintings due to the introduction of low-Z white pigments. In this investigation, we explored the possibilities of 4 less common radiographic techniques in order to circumvent the mentioned problems. For this, we applied the techniques on 4 panel paintings with an identical figurative composition made by the artist Peter Eyskens.

Several artists' pigments are semiconductors. Some of these materials appear stable over time, whereas others already show remarkable signs of degradation after limited time periods. The (in)stability of these pigments can be understood using a thermodynamic approach. For several pigment-related materials, the thermodynamic oxidation and reduction potential ( ϕ ox and ϕ red ) were determined and evaluated considering the absolute energy positions of the valence and conduction band edges and the water redox potentials. The positions of ϕ ox and ϕ red can be used in a fast screening of the stability of semiconductor pigments towards photoinduced corrosion in an aqueous/humid environment. This theoretical approach corresponds well with experimental data on pigment permanence and degradation phenomena found in literature.

Technological developments such as atmospheric plasma jets for industry can be adapted for the conservation of cultural heritage. This application might offer a potential method for the removal or transformation of the corrosion on historical photographs. We focus on daguerreotypes and present an in-depth study of the induced changes by a multi-analytical approach using optical microscopy, scanning electron microscopy, different types of transmission electron microscopy and X-ray absorption fine structure. The H2-He afterglow removes S from an Ag2S or Cu2S layer which results in a nano-layer of metallic Ag or Cu on top of the deteriorated microstructure. In case the corrosion layer is composed of Cu-Ag-S compounds, our proposed setup can be used to partially remove the corrosion. These alterations of the corrosion results in an improvement in the readability of the photographic image.

Radiography in transmission mode is a well-established technique to visualize the internal structure of paintings. However, for many paintings the pictorial layer cannot be clearly visualized with conventional radiography because of interference from paint on the reverse, the material composition or the regular structure of supports or subsurface layers. Traditional lead white grounds in particular cause specific imaging problems not encountered with more modern white pigments such as zinc and titanium whites. A solution to this problem is radiography in emission mode. This study demonstrates and articulates those factors that can interfere with visualization of a painting's pictorial layer using transmission radiography as well as those that contribute to the effectiveness of emission radiography in visualizing such information. While emission radiography has been applied to the examination of paintings for over half a century, it is a cumbersome technique that is further complicated by the need ...

There is a long tradition in evaluating industrial atmospheres by measuring the corrosion rate of exposed metal coupons. The heritage community also uses this method, but the interpretation of the corrosion rate often lacks clarity due to the low corrosivity in indoor museum environments. This investigation explores the possibilities and drawbacks of different silver corrosion rate assessments. The corrosion rate is determined by three approaches: (1) chemical characterization of metal coupons using analytical techniques such as electrochemical measurements, SEM-EDX, XRD, and µ-Raman spectroscopy, (2) continuous corrosion monitoring methods based on electrical resistivity loss of a corroding nm-sized metal wire and weight gain of a corroding silver coated quartz crystal, and (3) characterization of the visual degradation of the metal coupons. This study confirms that subtle differences in corrosivity between locations inside a museum can be determined on condition that the same corrosion rate assessment is used. However, the impact of the coupon orientation with respect to the prevailing direction of air circulation can be substantially larger than the impact of the coupon location.

Many historical silver objects are composed of sterling silver, a silver alloy containing small amounts of copper. Besides the dramatic impact of copper on the corrosion process, the chemical composition of the corrosion layer evolves continuously. The evolution of the surface during the exposure to a Na2S solution was monitored by means of visual observation at macroscopic level, chemical analysis at microscopic level and analysis at the nanoscopic level. The corrosion process starts with the preferential oxidation of copper, forming mixtures of oxides and sulphides while voids are being created beneath the corrosion layer. Only at a later stage, the silver below the corrosion layer is consumed. This results in the formation of jalpaite and at a later stage of acanthite. The acanthite is found inside the corrosion layer at the boundaries of jalpaite grains and as individual grains between the jalpaite grains but also as a thin film on top of the corrosion layer. The corrosion process could be described as a sequence of 5 subsequent surface states with transitions between these states.

One of the most striking but unexplained phenomena in the natural degradation of glass is the transformation of an almost colorless, transparent and homogeneous glass into a colored, opaque and heterogeneous degradation layer. In many cases, the degradation layer consists of numerous lamellae with a thickness between 0.1 and 10 pm. However, both internal structure and formation proess of laminated degradation layers remain unclear. In this paper, a model is proposed where we assume that transformed (degraded) glass consists of a random packing of nano-sized silica particles while the lamellae are the result of different packing densities. The model is able to connect the texture of numerous lamellae observed by several types of microscopic techniques with the structure at molecular level determined by means of chemical analysis. In addition, the model is able to explain numerous properties such as the parameters responsible for the contrast between lamellae. This contrast can be caused by differences in color, density, elemental composition, or surface roughness. (C) 2016 Elsevier B.V. All rights reserved.

The chemical composition of 11 glass panes originating from two 13th century non-figurative windows were analyzed by means of Scanning Electron MicroscopyEnergy Dispersive X-ray system (SEM-EDX). The windows were discovered in the back-wall of the triforium during the restoration of the choir of the cathedral St. Michael and St. Gudule in Brussels (Belgium). In order to determine if these windows were fabricated with glass of different origin or not, the compositional difference between the panes were compared with the variation in composition as a result of the following causes: (1) compositional fluctuation between panes cut from the same sheet of glass, (2) compositional fluctuation caused when panes are cut from different sheets that were made with the same batch, (3) compositional fluctuation caused when the glass is made from different batches at the same production center, and (4) compositional fluctuation as a result of glass produced at different fabrication centers.

In this study, the results of analysing of a series of 16th–19th century painted enamel objects of the Limoges School currently in collections in three Dutch and Flemish museums by means of portable and micro x-ray fluorescence analysis (PXRF and µ-XRF) and electron probe micro analysis (EPMA) are presented. The aim of the investigation was the authentication of specific pieces. Therefore, the glass compositions as well as the (glass) colouring agents used by the Limoges' artists were studied as a function of the age of the objects. Due to the evolution of these properties, it is possible to approximately date these objects based on their chemical composition. The complete ‘email peint’ collection of the Museum Boijmans-Van Beuningen (Rotterdam, The Netherlands), consisting of 20 ‘email peint’ plaques, was analysed with µ-XRF. Quantitative information was obtained by EPMA analysis of 15 enamel fragments of objects from museum and private collections in the Low Countries. PXRF analyses were performed on the painted enamel collection of the Antwerp Vleeshuis Museum (13 objects) and the Mayer van den Bergh Museum (4 objects) and on a set of 18 plaques that were donated to the Boijmans-Van Beuningen Museum by a private collector. The results obtained by means of EPMA, µ-XRF and PXRF proved to be useful in the discrimination of 16th century painted enamel objects from those of the19th century. From a total of 70 objects examined, 2 objects (OM964A and OM993) featured a chemical signature that deviated from the published literature composition and pigment use consistent with its presumed period of manufacture. Copyright © 2009 John Wiley & Sons, Ltd.

Background Precious objects made of silver and/or its alloys tarnish and become black when exposed to ambient atmospheres containing moisture and ppb-amounts of H 2 S. Such objects usually contain small but variable amounts of copper as alloying constituent and this affects the corrosion process due to a preferential oxidation of copper. However the visual appearance of the formed tarnishing layers on different types of silver alloys is very similar. Therefore, conservators-restorers are confronted with the problem that in some cases certain cleaning techniques are very effective while in other similar cases the removal of tarnishing layers is unsatisfactory. Since cleaning experiments are not allowed on genuine objects, many investigations use artificially corroded dummies instead. In order to evaluate the representativity and reproducibility of this often used methodology, differences in morphology, microstructure and composition of the sulfide layers on sterling silver generated by different sulfidation methods were analysed. Results Sterling silver samples were artificially aged in five different environments. The samples exposed to uncontrolled ambient air at different locations (e.g. residential and laboratory environments) showed different corrosion rates and corrosion colours. Three accelerated ageing methods were executed in a gaseous or liquid environment under controlled conditions. These tests showed different results in morphology, microstructure, composition, thickness and the interface between bulk and corrosion layer. A first accelerated sulfidation procedure in a Na 2 S solution alternated with exposure to air, resulted in a fast corrosion rate and an even corrosion layer formation with several S-species. A second series of sulfidation in a controlled gas environment of H 2 S and SO 2 developed a thin but uneven corrosion layer, mainly consisting of oxides. A third corrosion methodology used was based on the thioacetamide method. This resulted in an even and relative thick corrosion layer, comparable to the Na 2 S/aeration sulfidation system. However, the interface between the corrosion layer and the bulk is importantly different, showing severe voids. Conclusions The corrosion layers generated by five different experimental sulfidation series on identical prepared sterling silver coupons were clearly different from each other. Analyses demonstrated that the composition and microstructure of the corrosion layers were strongly dependent on the sulfidation method used and copper was found to be an important element present in all sulfide layers analysed. Therefore, artificially corroded sterling silver is not necessarily representative for naturally tarnished historical objects and the extrapolation of the cleaning results obtained on dummies to historical objects must be performed with care. Keywords: Cleaning evaluation; Silver alloy; Sulfidation; Copper enrichment; Silver enrichment; Heritage; Conservation-restoration

It is still unclear why some of the blue enamel on sixteenth- and seventeenth-century stained window glass is flaking off, while enamel layers with other colours are still in relatively good condition. In order to obtain a better understanding of this conservation problem, 31 historical recipes used for the fabrication of blue enamel were compared with results from the chemical analysis of 25 historic samples. The chemical composition and the microstructure of the enamels were analysed in cross-section by means of electron probe microanalysis (EPMA). This study demonstrated that the variation in chemical composition of the samples can be explained by the use of the wide range of recipes existing at that time. Although this study gave an insight into the composition, heterogeneity and use of colouring substances, no clear relation could be found between the parameters analysed and the deterioration rate of the blue enamel paint layer.

A variety of instrumental analytical techniques can be applied to the physical and chemical examination of works of art and archaeology. In this paper, a few examples are discussed of the application of micro-analytical chemistry in this interdisciplinary field. The following subjects from the experience of our laboratory, in collaboration with several specialized institutes, were selected: Early Bronze Age ceramic crucibles, residues and powders from Goltepe, South Central Turkey, have been analysed using surface analytical techniques to investigate potential evidence of tin smelting. The study indicates that the crucibles were used for processing of tin and gives clear evidence of a local tin industry. Roman glass from a collection of objects discovered in Qumrân near the Dead Sea was used to study the corrosion of glass objects in a particularly stable environment over a period of nearly 2000 years. The corrosion of a series of glass-in-lead windows from St. Michael and St. Goedele’s Cathedral, Brussels, was studied using electron probe microanalysis and micro X-ray fluorescence. New views can be formulated on the corrosion mechanism, which appears to be a complex multiphase process under the influence of atmospheric pollution. A few preliminary results are discussed for the analysis of glass paintings, in particular carnation red glass paints.

The world famous Alhambra monument in Granada, Southern Spain, listed as UNESCO world cultural heritage since 1984, represents probably the most beautiful example of Islamic art and architecture from the Middle Ages in Europe. It is visited by ca. 2 million people annually. Granada is situated in a natural basin, surrounded by mountains with altitudes up to 3500 m. Due to this topography and the prevailing low wind speeds, pollution-derived and especially traffic-derived particulate matter often accumulates in the urban air. In order to evaluate the potential conservation risks from the surrounding air, the atmospheric composition in the Alhambra monument was evaluated. Indoor temperature and relative humidity fluctuations were evaluated for their potential degenerative effects. Furthermore, the atmospheric composition in the Alhambra was analyzed in terms of inorganic gases (NO2, SO2, O3, and NH3) and black carbon. It was found that the open architecture protected the indoor environments from developing a potentially harmful microclimate, such as the build-up of humidity resulting from the huge number of daily tourists. On the downside, the strong ventilation made the indoor air hardly different from outdoor air, as characterized by strong diurnal temperature and relative humidity gradients and high traffic-derived pollutant levels.

X-ray radiographic images of paintings often show little or no contrast. In order to increase the contrast in radiographic images we measured the X-ray spectrum of a low power X-ray tube, after passing through the painting, with a high energy-resolution SDD detector. To obtain images, the detector is collimated with a 400 mu m diameter pinhole and the painting was moved through the beam in the x and y-direction using a dwell time of a few seconds per pixel. The data obtained consists of a data cube of, typically, 200 x 200 pixels and a 512-channel X-ray spectrum for each pixel, spanning the energy range from 0 to 40 keV. Having the absorbance spectrum available for each pixel, we are able, a posteriori, to produce images by edge subtraction for any given element. In this way high contrast, element-specific, images can be obtained. Because of the high energy-resolution a much simpler edge subtraction algorithm can be applied. We also used principal-component imaging to obtain, in a more automated way, images with high contrast. Some of these images can easily be attributed to specific elements. It turns out that preprocessing of the spectral data is crucial for the success of the multivariate image processing.

It is generally known that radiographic inspection of 1517th century paintings can easily be done with a polychromatic X-ray source using a voltage between 20 kV and 40 kV in combination with classic X-ray films. Unfortunately, the spatial structure of numerous 19th and early 20th century paintings cannot be visualized with conventional radiography due to several reasons such as the use of lead white grounds or low absorbing pigments. Radiographic images are blurred or worse, they do not contain the picture of the painting. During the last decades, many technological innovations have been introduced in the field of radiography but their possibilities in cultural heritage have not been explored in full detail. In our investigation we used phosphor imaging plates, energy dispersive detectors and CCD-cameras in combination with synchrotron radiation and conventional X-ray tubes in order to improve the quality of radiographic images. Several promising techniques that could improve the quality of radiographs of paintings were identified.

During the conservation of two stained glass windows by Jan de Caumont at the Abbey 't Park (Heverlee, Leuven, Belgium) small fragments were removed from eight panes for analysis. Electron microscopy with energy dispersive X-ray sprectroscopy (SEM-EDX) was used to study the microstructure of several materials in these windows, and to perform quantitative analysis of the homogeneous materials. According to the SEM-EDX analyses, the glass appeared to be homogeneous. The deteriorated regions found in the fragments contained cracks, have a fractal appearance with stratifications of 2 μm in width and contained small islands of original unleached glass. Unfortunately, SEM-EDX did not allow a reliable chemical analysis of the different stratified layers due to the limitation in lateral resolution. The vitreous paint layer on one of the fragments consisted of lead glass surrounding many SiO2 and Fe2O3 particles. The green-blue and blue enamel paint layers were made with a low-melting SiO2-K2O-PbO glass. ...