Katrien Keune | University of Amsterdam (original) (raw)

Papers by Katrien Keune

Research paper thumbnail of Variation in Dutch: From written MOGELIJK to spoken MOK

Corpus Linguistics and Linguistic Theory, 2005

Research paper thumbnail of New Tools for Old Masters : Conserving precious paintings for the art lovers of the future

The Analytical Scientist, Jul 1, 2019

Research paper thumbnail of Chemical characterisation of thin intermediate layers: Case study of a sample from the 15th century painting, The Descent from the Cross by Rogier van der Weyden

A combination of analytical microscopic techniques, which includes light microscopy (LM), Scannin... more A combination of analytical microscopic techniques, which includes light microscopy (LM), Scanning electron microscopy equipped with electron diffraction X-ray detection (SEM-EDX), Secondary Ion Mass Spectrometry (SIMS) and imaging FTIR were applied to study preparatory layers and in particular thin intermediate layers. The preparatory layers of the 15th century panel painting The Descent from the Cross by Rogier van der Weyden was investigated in a cross section taken from the virgin’s blue robe. High magnification SEM and nano-SIMS are reported here. The isolation or intermediate layer is characterised by the higher concentration of carbon in comparison to the adjacent layers, interpreted as being richer in organic binding medium. SIMS data suggests the presence of oleaginous binding media. Nano-SIMS gives no indication of the presence of proteins suggesting the medium is is not an emulsion. Only a few lead white particles are found in the layer. However SEM EDX mapping shows that...

Research paper thumbnail of Imaging Microspectroscopic, Secondary Ion Mass Spectrometric and Electron Microscopic Studies on Discoloured and Partially Discoloured Smalt in Cross-sections of 16th Century Paintings

CHIMIA International Journal for Chemistry

Paint cross-sections of five 16th century paintings with areas of discoloured smalt oil paint wer... more Paint cross-sections of five 16th century paintings with areas of discoloured smalt oil paint were investigated. Semi-quantitative SEM-EDX analysis revealed that potassium was relatively low in all discoloured smalts, while cobalt remained at an approximately steady level. Reflection light microscopy demonstrated the presence of partially discoloured smalt particles with a remaining blue core. Imaging SIMS demonstrated that cobalt has a uniform distribution in the glass particles. Potassium however shows relatively high levels in the oil paint matrix around the discoloured glass particles and an uneven distribution in smalt particles with a blue core. These blue cores always have a higher K level compared to the discoloured rim of the particle. The loss of potassium from smalt in oil paint is interpreted as a leaching process which lowers the basicity of the glass below a critical level for colour maintenance. The colour change of the smalt is thus an indicator of a change in alkali...

Research paper thumbnail of The occurrence of artificial orpiment (dry process) in northern European painting and polychromy and evidence in historical sources

Research paper thumbnail of Characterization and localization of the oil-binding medium in paint cross-sections using imaging secondary ion mass spectrometry

Saturated monocarboxylic fatty acids (namely palmitic acid and stearic acid, which are markers fo... more Saturated monocarboxylic fatty acids (namely palmitic acid and stearic acid, which are markers for the type of oil used in paintings) can be identified with imaging secondary ion mass spectrometry (SIMS), while retaining spatial information. The P:S ratios presented were determined with negative ion SIMS in individual layers of paint cross-sections from 15th to 19th century paintings. The positive ion mass spectrum gives information about the speciation of the fatty acids (free, ester-bound or metal carboxylates), indicative of the drying stage of the oil. Studies on freshly applied multi-layered oil paint systems suggest the diffusion of oil triglycerides between layers, which will influence the P:S ratio.

Research paper thumbnail of Auripigment / Orpiment. Studien zu dem Mineral und den künstlichen Produkten / Studies on the mineral and the artificial products

Contents Carolin Rötter: Natürliches und künstliches Auripigment - unter Einbeziehung von Realgar... more Contents Carolin Rötter: Natürliches und künstliches Auripigment - unter Einbeziehung von Realgar. Pages 7 - 102 Günter Grundmann, Carolin Rötter: 'Artificial orpiment': microscopic, diffractometric and chemical characteristics of synthesis products in comparison to natural orpiment. Pages 103 - 140. "Künstliches Auripigment": Mikroskopische, diffractometrische und chemische Charakteristic von Syntheseprodukten im Vergleich zu natürlichem Auripigment. Pages 141 - 166. Mark Richter, Günter Grundmann, Annelies van Loon, Katrien Keune, Annetje Boersma, Klaus Rapp: The occurrence of artificial orpiment (dry process) in northern European painting and polychromy and evidence in historical sources. Pages 167 - 192.

Research paper thumbnail of Binding media in Tudor and Jacobean portrait paintings – distinguishing between original paint and conservation additions

This paper presents the results of analyses of binding media and organic additives in 25 portrait... more This paper presents the results of analyses of binding media and organic additives in 25 portrait paintings from the Tudor and Jacobean periods. Results are discussed in the light of historical paint technology. The complementarity of micro-destructive detailed analysis of GC/MS and spatially resolved analytical information on the presence of media and additions in individual layers as analysed with attenuated total reflection (ATR) FTIR imaging is discussed. MALDI-ToF mass spectrometry analysis is presented for the specific analysis of proteinaceous binding media. In painting grounds, the use of bovine animal glue could be confirmed. Special attention was paid to black paint systems used for garments and backgrounds. Most paints contained light-bleached and/or heat-bodied linseed oil with some pine resin addition. These media are responsible for richly saturated and bodied paints in the paintings, many of which wereapplied in multiple glazing layers. The potential for distinction b...

Research paper thumbnail of An infrared spectroscopic study of the nature of zinc carboxylates in oil paintings

J. Anal. At. Spectrom., 2015

A systematic search to explain the COO− vibration band shift for zinc carboxylates formed in a wo... more A systematic search to explain the COO− vibration band shift for zinc carboxylates formed in a work by van Gogh.

Research paper thumbnail of An Investigation into the Viability of Removal of Lead Soap Efflorescence from Contemporary Oil Paintings

Issues in Contemporary Oil Paint, 2014

Research paper thumbnail of Novel mass spectrometric approaches for the analysis of modern oil paint media and organic additives in paintings

Research paper thumbnail of Its Surreal: Zinc-Oxide Degradation and Misperceptions in Salvador Dalí’s Couple with Clouds in Their Heads, 1936

Issues in Contemporary Oil Paint, 2014

Research paper thumbnail of Decomposing Apricots: Tracking Transformation of Arsenic Sulfide pigments in a Dutch Golden Age Still-life

Microscopy and Microanalysis, 2014

Arsenic sulfide based yellow and red/orange pigments, orpiment (As 2 S 3) and realgar (As 4 S 4),... more Arsenic sulfide based yellow and red/orange pigments, orpiment (As 2 S 3) and realgar (As 4 S 4), have been used since antiquity. Though absent in Europe in middle-ages, these pigments came back from Asia Minor via Venice in the 15 th century. They were frequently used to paint furniture and historic interiors, often in place of gold. They were less common in easel paintings, but towards the end of the 17 th century they made a comeback, particularly in still-lifes. The late 18 th century saw gradual replacement of the Arsenic pigments by new pigments created by the revolution in chemistry. Arsenic sulfide pigments are known to shift color under exposure to light. Realgar undergoes photoinduced polymorphism and turns bright yellow (to para-realgar) to colorless, whereas orpiment photooxidizes and becomes colorless. In here, we report on this transformation and characterization of the reaction products, based on investigation of two very different works of art from early 18 th century: Still life with five apricots by the Dutch master Adriaen Coorte (1704) (Royal Picture Gallery Mauritshuis, The Hague, The Netherlands) and an early American polychromed chest on stand attributed to Charles Guillam painted in Saybrook, Connecticut between 1710-1727 (Winterthur Museum, Wintherthur, USA). The small oil painting is painted on a thick yellow earth pigmented ground layer on canvas. Realgar, mixed with organic lake on gypsum substrate, is used in the paint build up of the apricots, with the highlights painted in vermilion. The apricots show signs of degradation. The paint layer is very crumbly, especially along the cracks, and appears to be vulnerable to further degradation when exposed to moisture and solvents. The Saybrook chest is painted in distemper, a proteinaceous binding medium, with foliate, crown and thistle, and fleur de lis motifs. The regions that were once painted with arsenic sulfide now have a mottled appearance of ivory and brown. We used spectromicroscopy at an X-ray microprobe at Stanford Synchrotron Radiation Lightsource, supplemented by optical, infrared, and backscatter electron microscopy, Raman microspectroscopy. In here, we will focus on the X-ray results : X-ray fluorescence mode (XRF scanning) allowed precise mapping of local elemental distribution, while X-ray Near-Edge Absorption Structure (XANES) in combination with multi-energy XRF mode allowed identification and mapping of the gross chemical speciation. Cross-sectioned samples for these measurements were mounted in polyester resin blocks, and dry hand-polished.

Research paper thumbnail of Degradation of Emerald green in oil paint and its contribution to the rapid change in colour of the Descente des vaches (1834–1835) painted by Théodore Rousseau

Studies in Conservation, 2013

Descente des vaches (1836) by Théodore Rousseau in the Mesdag Collection in The Hague is barely r... more Descente des vaches (1836) by Théodore Rousseau in the Mesdag Collection in The Hague is barely readable and its paint layers are in poor condition. The surface of the painting is strongly deformed and cracked, the whole painting has darkened and especially the greens have lost all or most of their colour resulting in brown passages. Large passages of the painting that were painted with multiple thick and medium-rich layers have darkened dramatically. This paper proposes that the degradation of Emerald green (Cu(C 2 H 3 O 2) 2 •3Cu(AsO 2) 2 , copperacetoarsenite)the main green pigment used in this paintingis a significant factor in the cause of the darkening. Electron backscatter images reveal that the Emerald green particles are shown different degrees of degradation: from partially to completely disintegrated. Elemental maps show that arsenic is distributed throughout the paint cross section, with relatively higher concentrations around iron-and aluminium-containing particles, and in the varnish layer. Imaging-Fouriertransform infrared microscopy detects copper soaps in the degraded Emerald green-containing layers. Analytical data from four paint cross sections strongly suggest that Emerald green reacts with free fatty acids derived from the binding medium forming copper soaps and mobile arsenic-based species. Chemical laboratory experiments fully support this hypothesis. Emerald green and palmitic acid in chloroform form copper palmitate and arsenic trioxide (arsenolite, cubic) under room temperature and normal light conditions. The degradation of Emerald green particles in Descente des vaches has resulted in a loss of light-reflecting surfaces and in newly formed compounds in the paint, both contribute to the colour change from green to brown.

Research paper thumbnail of Imaging Analytical Studies of Old Master Paints Using FTIR, SIMS and SEMEDX of Embedded Paint Cross Sections

Microscopy and Microanalysis, 2005

The composition of paint layers in paintings is a challenge for the microscopic analyst of painti... more The composition of paint layers in paintings is a challenge for the microscopic analyst of paintings. In comparison to modern composites, the original materials in paintings no longer exist and analytical methods have to be adapted to meet the challenges of the small size of the available sample, the variable oxidation state and the difficulties of separating oxidised condensation polymers and inorganic fractions in the paint. The paint layer structure imposes its own complexities since each layer has unique properties: variable thickness, mixed mineral phases in different particle size distributions, and unique binding medium signatures. Thus, the combined application of spatially resolved analytical techniques using imaging FTIR (FT-6000 Stingray, Digilabs Inc), SEMEDX (FEI XL30 SFEG with EDAX EDX analysis) and static SIMS (TRIFT II; Phy Electronics Inc) is our preferred approach [1]. The quality of the surface is of crucial importance to obtain any results. In our hands this is accomplished first by wet grinding to thin the embedding material around a paint chip and subsequently dry polishing with an in-house designed sample holder that can feed in micrometer steps using Micromesh cloths up to 12000 mesh. Under these conditions FTIR imaging presents the chemical functional group distribution, while SIMS gives information about the nature of fatty acids, fatty acyl moieties, metal carboxylates and proteins. Both SIMS and SEMEDX mapping give complimentary elemental information. An example is presented. The ultramarine colored paint (made from "lapis lazuli") from the painting "The Descent from the Cross" by Rogier van der Weyden (1400-1464) was studied earlier with a focus on the distribution of oil derived constituents in the paint cross section using imaging SIMS and FTIR [1]. An important remaining problem was the composition of a few several micron thick layers just visible by light microscopy. These layers are part of the preparatory process of the painting and could contain evidence for the methodology of underdrawing and imprematura. The layers were too thin for imaging FTIR. SIMS maps demonstrate the presence of lead, calcium and fatty acids (C16FA and C18FA imaged as negative ions) in this layer. We report here SEMEDX data at 2500x using a 10 kV acceleration voltage to limit the elemental information to the more surfacial layers. A BSE map and element maps of lead, calcium, and carbon are presented in (Fig 1 AD). No data could be obtained for nitrogen, a potential component of an proteinaceous emulsion paint. The preparatory layer b is highlighted in yellow in Fig 1. Highly reflecting particles in the BSE map represent lead white. Calcium carbonate and azurite (copperhydroxycarbonate) have lower electron reflectivities. Calcium (1C) is mainly present in the chalk ground (layer c) with some individual particles in layer b. Azurite is only present in layer a (see the dark spots upper left in the lead distribution). The lead map (1D) matches the

Research paper thumbnail of Selective C−H Bond Activation with Na2PtCl4 in Inverted Micelles

European Journal of Inorganic Chemistry, 2000

The selective C−H activation of n-heptane and methylcyclohexane with Na 2 PtCl 4 under mild condi... more The selective C−H activation of n-heptane and methylcyclohexane with Na 2 PtCl 4 under mild conditions in water in inverted micelles is described.

Research paper thumbnail of Imaging Analytical Studies of Lead Soaps Aggregating in Preprimed Canvas Used by the Hudson River Painter F.E. Church

Microscopy and Microanalysis, 2005

Research paper thumbnail of Analytical Imaging Studies of Cross-Sections of Paintings Affected by Lead Soap Aggregate Formation

Studies in Conservation, 2007

ABSTRACT Lead soap aggregateshave been-found in lead-containing oil paint layers in paintings fro... more ABSTRACT Lead soap aggregateshave been-found in lead-containing oil paint layers in paintings from the thirteenth to the twentieth century. They severely affect the stability of the paint layers and disturb the surface of the paintings. Paint cross-sectionsfrom five paintings affected by lead soaps were selected to illustrate and investigate this degradation phenomenon with the analytical imaging techniques of Fourier transform infrared spectroscopy, secondary ion mass spectrometry and scanning electron microscopy combined with X-ray analysis. Examples aregiven of lead soapsforming in a mature paint system or, alternatively, in the early drying stage of the oil; lead soapsforming from various types of lead-containing pigments or driers; lead soapsforming in multiple paint layers; and lead-containing crystallization products inside aggregates. The phenomenon of lead soap aggregatesis multifaceted, and one general scenario describing theformation of lead soap aggregatescannot explain all aspects. However, the integration of the chemical information and its distribution among the paint layers leads to the proposal that reactivefree monocarboxylicfatty acids playa key role in lead soap aggregateformation. The availability and release of thesefatty acids depends on the original paint composition, the build-up of the layers, and the conservation/environmental exposure history of the painting.

Research paper thumbnail of Analytical imaging studies clarifying the process of the darkening of vermilion in paintings

Analytical chemistry, 2005

Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross secti... more Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross sections with degraded vermilion (red mercury sulfide) paint to cast new light on the well-known problem of its light-induced darkening. The static SIMS data are combined with light microscopic, electron microscopic studies and energy-dispersive X-ray analysis to identify and localize the various reaction products. The spatial distribution of atomic and molecular species in paint cross sections of the native vermilion and the reaction products leads to the formulation of a new hypothesis on the reaction mechanism of the photodegradation of vermilion where two black and white reaction products are formed sequentially. Under the influence of light, some of the vermilion (HgS) is converted into Hg(0) and S(0). In this process, the chlorine ions, present in the native vermilion, act as a catalyst. We propose that the Hg(0) is deposited on the surface of the remaining HgS as elementary mercury nan...

Research paper thumbnail of The molecular structure of three types of long-chain zinc(II) alkanoates for the study of oil paint degradation

Polyhedron, 2014

The molecular structures of three types of zinc(II) alkanoates (Zn(C n ) 2 , ZnNa 2 (C n ) 4 and ... more The molecular structures of three types of zinc(II) alkanoates (Zn(C n ) 2 , ZnNa 2 (C n ) 4 and ZnK 2 (C n ) 4 , C n = CH 3 (CH 2 ) nÀ2 COO À , n = 8-18) were investigated by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) to aid the study of degradation phenomena in oil paint. Each type of complex forms a homologous series in the studied chain length range. For (Zn(C n ) 2 and ZnNa 2 (C n ) 4 , these homologous series indicate that the long-chain complexes have structures highly similar to those published for short-chain single-crystal analogs. Moreover, we introduce a chain tilt factor F tilt to derive information about alkanoate chain angles from highly accurate PXRD long spacing values. The complex ZnK 2 (C n ) 4 has not been reported before. It consists of metal sheets containing tetrahedrally coordinated Zn atoms and octahedrally coordinated K atoms bridged by effectively monodentate carboxylate groups, and alkanoate chains that are tilted relative to the long axis.

Research paper thumbnail of Variation in Dutch: From written MOGELIJK to spoken MOK

Corpus Linguistics and Linguistic Theory, 2005

Research paper thumbnail of New Tools for Old Masters : Conserving precious paintings for the art lovers of the future

The Analytical Scientist, Jul 1, 2019

Research paper thumbnail of Chemical characterisation of thin intermediate layers: Case study of a sample from the 15th century painting, The Descent from the Cross by Rogier van der Weyden

A combination of analytical microscopic techniques, which includes light microscopy (LM), Scannin... more A combination of analytical microscopic techniques, which includes light microscopy (LM), Scanning electron microscopy equipped with electron diffraction X-ray detection (SEM-EDX), Secondary Ion Mass Spectrometry (SIMS) and imaging FTIR were applied to study preparatory layers and in particular thin intermediate layers. The preparatory layers of the 15th century panel painting The Descent from the Cross by Rogier van der Weyden was investigated in a cross section taken from the virgin’s blue robe. High magnification SEM and nano-SIMS are reported here. The isolation or intermediate layer is characterised by the higher concentration of carbon in comparison to the adjacent layers, interpreted as being richer in organic binding medium. SIMS data suggests the presence of oleaginous binding media. Nano-SIMS gives no indication of the presence of proteins suggesting the medium is is not an emulsion. Only a few lead white particles are found in the layer. However SEM EDX mapping shows that...

Research paper thumbnail of Imaging Microspectroscopic, Secondary Ion Mass Spectrometric and Electron Microscopic Studies on Discoloured and Partially Discoloured Smalt in Cross-sections of 16th Century Paintings

CHIMIA International Journal for Chemistry

Paint cross-sections of five 16th century paintings with areas of discoloured smalt oil paint wer... more Paint cross-sections of five 16th century paintings with areas of discoloured smalt oil paint were investigated. Semi-quantitative SEM-EDX analysis revealed that potassium was relatively low in all discoloured smalts, while cobalt remained at an approximately steady level. Reflection light microscopy demonstrated the presence of partially discoloured smalt particles with a remaining blue core. Imaging SIMS demonstrated that cobalt has a uniform distribution in the glass particles. Potassium however shows relatively high levels in the oil paint matrix around the discoloured glass particles and an uneven distribution in smalt particles with a blue core. These blue cores always have a higher K level compared to the discoloured rim of the particle. The loss of potassium from smalt in oil paint is interpreted as a leaching process which lowers the basicity of the glass below a critical level for colour maintenance. The colour change of the smalt is thus an indicator of a change in alkali...

Research paper thumbnail of The occurrence of artificial orpiment (dry process) in northern European painting and polychromy and evidence in historical sources

Research paper thumbnail of Characterization and localization of the oil-binding medium in paint cross-sections using imaging secondary ion mass spectrometry

Saturated monocarboxylic fatty acids (namely palmitic acid and stearic acid, which are markers fo... more Saturated monocarboxylic fatty acids (namely palmitic acid and stearic acid, which are markers for the type of oil used in paintings) can be identified with imaging secondary ion mass spectrometry (SIMS), while retaining spatial information. The P:S ratios presented were determined with negative ion SIMS in individual layers of paint cross-sections from 15th to 19th century paintings. The positive ion mass spectrum gives information about the speciation of the fatty acids (free, ester-bound or metal carboxylates), indicative of the drying stage of the oil. Studies on freshly applied multi-layered oil paint systems suggest the diffusion of oil triglycerides between layers, which will influence the P:S ratio.

Research paper thumbnail of Auripigment / Orpiment. Studien zu dem Mineral und den künstlichen Produkten / Studies on the mineral and the artificial products

Contents Carolin Rötter: Natürliches und künstliches Auripigment - unter Einbeziehung von Realgar... more Contents Carolin Rötter: Natürliches und künstliches Auripigment - unter Einbeziehung von Realgar. Pages 7 - 102 Günter Grundmann, Carolin Rötter: 'Artificial orpiment': microscopic, diffractometric and chemical characteristics of synthesis products in comparison to natural orpiment. Pages 103 - 140. "Künstliches Auripigment": Mikroskopische, diffractometrische und chemische Charakteristic von Syntheseprodukten im Vergleich zu natürlichem Auripigment. Pages 141 - 166. Mark Richter, Günter Grundmann, Annelies van Loon, Katrien Keune, Annetje Boersma, Klaus Rapp: The occurrence of artificial orpiment (dry process) in northern European painting and polychromy and evidence in historical sources. Pages 167 - 192.

Research paper thumbnail of Binding media in Tudor and Jacobean portrait paintings – distinguishing between original paint and conservation additions

This paper presents the results of analyses of binding media and organic additives in 25 portrait... more This paper presents the results of analyses of binding media and organic additives in 25 portrait paintings from the Tudor and Jacobean periods. Results are discussed in the light of historical paint technology. The complementarity of micro-destructive detailed analysis of GC/MS and spatially resolved analytical information on the presence of media and additions in individual layers as analysed with attenuated total reflection (ATR) FTIR imaging is discussed. MALDI-ToF mass spectrometry analysis is presented for the specific analysis of proteinaceous binding media. In painting grounds, the use of bovine animal glue could be confirmed. Special attention was paid to black paint systems used for garments and backgrounds. Most paints contained light-bleached and/or heat-bodied linseed oil with some pine resin addition. These media are responsible for richly saturated and bodied paints in the paintings, many of which wereapplied in multiple glazing layers. The potential for distinction b...

Research paper thumbnail of An infrared spectroscopic study of the nature of zinc carboxylates in oil paintings

J. Anal. At. Spectrom., 2015

A systematic search to explain the COO− vibration band shift for zinc carboxylates formed in a wo... more A systematic search to explain the COO− vibration band shift for zinc carboxylates formed in a work by van Gogh.

Research paper thumbnail of An Investigation into the Viability of Removal of Lead Soap Efflorescence from Contemporary Oil Paintings

Issues in Contemporary Oil Paint, 2014

Research paper thumbnail of Novel mass spectrometric approaches for the analysis of modern oil paint media and organic additives in paintings

Research paper thumbnail of Its Surreal: Zinc-Oxide Degradation and Misperceptions in Salvador Dalí’s Couple with Clouds in Their Heads, 1936

Issues in Contemporary Oil Paint, 2014

Research paper thumbnail of Decomposing Apricots: Tracking Transformation of Arsenic Sulfide pigments in a Dutch Golden Age Still-life

Microscopy and Microanalysis, 2014

Arsenic sulfide based yellow and red/orange pigments, orpiment (As 2 S 3) and realgar (As 4 S 4),... more Arsenic sulfide based yellow and red/orange pigments, orpiment (As 2 S 3) and realgar (As 4 S 4), have been used since antiquity. Though absent in Europe in middle-ages, these pigments came back from Asia Minor via Venice in the 15 th century. They were frequently used to paint furniture and historic interiors, often in place of gold. They were less common in easel paintings, but towards the end of the 17 th century they made a comeback, particularly in still-lifes. The late 18 th century saw gradual replacement of the Arsenic pigments by new pigments created by the revolution in chemistry. Arsenic sulfide pigments are known to shift color under exposure to light. Realgar undergoes photoinduced polymorphism and turns bright yellow (to para-realgar) to colorless, whereas orpiment photooxidizes and becomes colorless. In here, we report on this transformation and characterization of the reaction products, based on investigation of two very different works of art from early 18 th century: Still life with five apricots by the Dutch master Adriaen Coorte (1704) (Royal Picture Gallery Mauritshuis, The Hague, The Netherlands) and an early American polychromed chest on stand attributed to Charles Guillam painted in Saybrook, Connecticut between 1710-1727 (Winterthur Museum, Wintherthur, USA). The small oil painting is painted on a thick yellow earth pigmented ground layer on canvas. Realgar, mixed with organic lake on gypsum substrate, is used in the paint build up of the apricots, with the highlights painted in vermilion. The apricots show signs of degradation. The paint layer is very crumbly, especially along the cracks, and appears to be vulnerable to further degradation when exposed to moisture and solvents. The Saybrook chest is painted in distemper, a proteinaceous binding medium, with foliate, crown and thistle, and fleur de lis motifs. The regions that were once painted with arsenic sulfide now have a mottled appearance of ivory and brown. We used spectromicroscopy at an X-ray microprobe at Stanford Synchrotron Radiation Lightsource, supplemented by optical, infrared, and backscatter electron microscopy, Raman microspectroscopy. In here, we will focus on the X-ray results : X-ray fluorescence mode (XRF scanning) allowed precise mapping of local elemental distribution, while X-ray Near-Edge Absorption Structure (XANES) in combination with multi-energy XRF mode allowed identification and mapping of the gross chemical speciation. Cross-sectioned samples for these measurements were mounted in polyester resin blocks, and dry hand-polished.

Research paper thumbnail of Degradation of Emerald green in oil paint and its contribution to the rapid change in colour of the Descente des vaches (1834–1835) painted by Théodore Rousseau

Studies in Conservation, 2013

Descente des vaches (1836) by Théodore Rousseau in the Mesdag Collection in The Hague is barely r... more Descente des vaches (1836) by Théodore Rousseau in the Mesdag Collection in The Hague is barely readable and its paint layers are in poor condition. The surface of the painting is strongly deformed and cracked, the whole painting has darkened and especially the greens have lost all or most of their colour resulting in brown passages. Large passages of the painting that were painted with multiple thick and medium-rich layers have darkened dramatically. This paper proposes that the degradation of Emerald green (Cu(C 2 H 3 O 2) 2 •3Cu(AsO 2) 2 , copperacetoarsenite)the main green pigment used in this paintingis a significant factor in the cause of the darkening. Electron backscatter images reveal that the Emerald green particles are shown different degrees of degradation: from partially to completely disintegrated. Elemental maps show that arsenic is distributed throughout the paint cross section, with relatively higher concentrations around iron-and aluminium-containing particles, and in the varnish layer. Imaging-Fouriertransform infrared microscopy detects copper soaps in the degraded Emerald green-containing layers. Analytical data from four paint cross sections strongly suggest that Emerald green reacts with free fatty acids derived from the binding medium forming copper soaps and mobile arsenic-based species. Chemical laboratory experiments fully support this hypothesis. Emerald green and palmitic acid in chloroform form copper palmitate and arsenic trioxide (arsenolite, cubic) under room temperature and normal light conditions. The degradation of Emerald green particles in Descente des vaches has resulted in a loss of light-reflecting surfaces and in newly formed compounds in the paint, both contribute to the colour change from green to brown.

Research paper thumbnail of Imaging Analytical Studies of Old Master Paints Using FTIR, SIMS and SEMEDX of Embedded Paint Cross Sections

Microscopy and Microanalysis, 2005

The composition of paint layers in paintings is a challenge for the microscopic analyst of painti... more The composition of paint layers in paintings is a challenge for the microscopic analyst of paintings. In comparison to modern composites, the original materials in paintings no longer exist and analytical methods have to be adapted to meet the challenges of the small size of the available sample, the variable oxidation state and the difficulties of separating oxidised condensation polymers and inorganic fractions in the paint. The paint layer structure imposes its own complexities since each layer has unique properties: variable thickness, mixed mineral phases in different particle size distributions, and unique binding medium signatures. Thus, the combined application of spatially resolved analytical techniques using imaging FTIR (FT-6000 Stingray, Digilabs Inc), SEMEDX (FEI XL30 SFEG with EDAX EDX analysis) and static SIMS (TRIFT II; Phy Electronics Inc) is our preferred approach [1]. The quality of the surface is of crucial importance to obtain any results. In our hands this is accomplished first by wet grinding to thin the embedding material around a paint chip and subsequently dry polishing with an in-house designed sample holder that can feed in micrometer steps using Micromesh cloths up to 12000 mesh. Under these conditions FTIR imaging presents the chemical functional group distribution, while SIMS gives information about the nature of fatty acids, fatty acyl moieties, metal carboxylates and proteins. Both SIMS and SEMEDX mapping give complimentary elemental information. An example is presented. The ultramarine colored paint (made from "lapis lazuli") from the painting "The Descent from the Cross" by Rogier van der Weyden (1400-1464) was studied earlier with a focus on the distribution of oil derived constituents in the paint cross section using imaging SIMS and FTIR [1]. An important remaining problem was the composition of a few several micron thick layers just visible by light microscopy. These layers are part of the preparatory process of the painting and could contain evidence for the methodology of underdrawing and imprematura. The layers were too thin for imaging FTIR. SIMS maps demonstrate the presence of lead, calcium and fatty acids (C16FA and C18FA imaged as negative ions) in this layer. We report here SEMEDX data at 2500x using a 10 kV acceleration voltage to limit the elemental information to the more surfacial layers. A BSE map and element maps of lead, calcium, and carbon are presented in (Fig 1 AD). No data could be obtained for nitrogen, a potential component of an proteinaceous emulsion paint. The preparatory layer b is highlighted in yellow in Fig 1. Highly reflecting particles in the BSE map represent lead white. Calcium carbonate and azurite (copperhydroxycarbonate) have lower electron reflectivities. Calcium (1C) is mainly present in the chalk ground (layer c) with some individual particles in layer b. Azurite is only present in layer a (see the dark spots upper left in the lead distribution). The lead map (1D) matches the

Research paper thumbnail of Selective C−H Bond Activation with Na2PtCl4 in Inverted Micelles

European Journal of Inorganic Chemistry, 2000

The selective C−H activation of n-heptane and methylcyclohexane with Na 2 PtCl 4 under mild condi... more The selective C−H activation of n-heptane and methylcyclohexane with Na 2 PtCl 4 under mild conditions in water in inverted micelles is described.

Research paper thumbnail of Imaging Analytical Studies of Lead Soaps Aggregating in Preprimed Canvas Used by the Hudson River Painter F.E. Church

Microscopy and Microanalysis, 2005

Research paper thumbnail of Analytical Imaging Studies of Cross-Sections of Paintings Affected by Lead Soap Aggregate Formation

Studies in Conservation, 2007

ABSTRACT Lead soap aggregateshave been-found in lead-containing oil paint layers in paintings fro... more ABSTRACT Lead soap aggregateshave been-found in lead-containing oil paint layers in paintings from the thirteenth to the twentieth century. They severely affect the stability of the paint layers and disturb the surface of the paintings. Paint cross-sectionsfrom five paintings affected by lead soaps were selected to illustrate and investigate this degradation phenomenon with the analytical imaging techniques of Fourier transform infrared spectroscopy, secondary ion mass spectrometry and scanning electron microscopy combined with X-ray analysis. Examples aregiven of lead soapsforming in a mature paint system or, alternatively, in the early drying stage of the oil; lead soapsforming from various types of lead-containing pigments or driers; lead soapsforming in multiple paint layers; and lead-containing crystallization products inside aggregates. The phenomenon of lead soap aggregatesis multifaceted, and one general scenario describing theformation of lead soap aggregatescannot explain all aspects. However, the integration of the chemical information and its distribution among the paint layers leads to the proposal that reactivefree monocarboxylicfatty acids playa key role in lead soap aggregateformation. The availability and release of thesefatty acids depends on the original paint composition, the build-up of the layers, and the conservation/environmental exposure history of the painting.

Research paper thumbnail of Analytical imaging studies clarifying the process of the darkening of vermilion in paintings

Analytical chemistry, 2005

Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross secti... more Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross sections with degraded vermilion (red mercury sulfide) paint to cast new light on the well-known problem of its light-induced darkening. The static SIMS data are combined with light microscopic, electron microscopic studies and energy-dispersive X-ray analysis to identify and localize the various reaction products. The spatial distribution of atomic and molecular species in paint cross sections of the native vermilion and the reaction products leads to the formulation of a new hypothesis on the reaction mechanism of the photodegradation of vermilion where two black and white reaction products are formed sequentially. Under the influence of light, some of the vermilion (HgS) is converted into Hg(0) and S(0). In this process, the chlorine ions, present in the native vermilion, act as a catalyst. We propose that the Hg(0) is deposited on the surface of the remaining HgS as elementary mercury nan...

Research paper thumbnail of The molecular structure of three types of long-chain zinc(II) alkanoates for the study of oil paint degradation

Polyhedron, 2014

The molecular structures of three types of zinc(II) alkanoates (Zn(C n ) 2 , ZnNa 2 (C n ) 4 and ... more The molecular structures of three types of zinc(II) alkanoates (Zn(C n ) 2 , ZnNa 2 (C n ) 4 and ZnK 2 (C n ) 4 , C n = CH 3 (CH 2 ) nÀ2 COO À , n = 8-18) were investigated by Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) to aid the study of degradation phenomena in oil paint. Each type of complex forms a homologous series in the studied chain length range. For (Zn(C n ) 2 and ZnNa 2 (C n ) 4 , these homologous series indicate that the long-chain complexes have structures highly similar to those published for short-chain single-crystal analogs. Moreover, we introduce a chain tilt factor F tilt to derive information about alkanoate chain angles from highly accurate PXRD long spacing values. The complex ZnK 2 (C n ) 4 has not been reported before. It consists of metal sheets containing tetrahedrally coordinated Zn atoms and octahedrally coordinated K atoms bridged by effectively monodentate carboxylate groups, and alkanoate chains that are tilted relative to the long axis.