Cadmium Yellow Research Articles

Cadmium Yellow Pigments in Oil Paintings: Optical Degradation Studies Utilizing 3D Fluorescence Mapping Supported by Raman Spectroscopy and Colorimetry

The degradation of cadmium yellow in paintings is influenced by various factors, primarily environmental conditions and light exposure. Applying a thin protective layer of linseed oil on the surface could help mitigate these processes. Linseed oil, being a natural material, acts as a barrier against harmful atmospheric agents like moisture and oxygen, which contribute to the degradation of pigments including cadmium yellow. Additionally, linseed oil reduces direct light exposure, thereby lowering the risk of fading and color alteration. In this study, we explored the degradation of cadmium pigments mixed with oil and applied on canvas. We elucidated how the use of a binder prevents the direct oxidation of the pigment, inducing artificial degradation by irradiating samples with UVA (365 nm) and UVC (250 nm) sources. By employing various spectroscopic techniques such as three-dimensional fluorescence mapping (PLE) and Raman, along with colorimetric analysis, we gained a comprehensive understanding of the degradation process, particularly when linseed oil serves as a protective layer.

Studies of thermal decomposition of poly(vinyl chloride) composition with cadmium yellow and stearic acid

The article presents research on the thermal decomposition of individual ingredients and compositions that are physical mixtures of emulsion poly(vinyl chloride) (PVC), cadmium yellow, and stearic acid. The results of the tests were TG, DTA, and DTG graphs. From their course, the initial decomposition temperatures, maximum decomposition rate, and final temperatures were determined, and changes in the mass of samples and the values of thermal effects were calculated. The influence of pigment and stearic acid on the thermal decomposition of PVC was investigated. Cadmium yellow, modified in an alkaline medium and containing hydroxyl groups, was also used for the tests. It was found that the presence of both pigment and stearic acid had a retarding effect on the initiation of thermal decomposition of PVC. The addition of CdS modified in an alkaline environment had a more or less similar effect on the initial decomposition temperature of PVC. Depending on the composition of the polymer and the value of the final temperature, different values of thermal effects and the amount of products formed were indicated.

Painting on the margins: investigating the pigments, media, and techniques of Séraphine Louis

The richly decorative and imaginative works by French artist Séraphine Louis (1864–1942) have long elicited fascination, and her working methods have often eluded art historians and conservators alike. Working in secret and outside established art circles, Séraphine employed materials such as natural resin varnishes and was said to have used household paints in addition to traditional artists' oil paints. In this study of six works in the collections of the Musée d'Art et d'Archéologie, Senlis (MAA), The Museum of Modern Art, New York (MoMA), and The Metropolitan Museum of Art, New York (MMA), attention was given to Séraphine's choice of colors and paints, in addition to identifying possible additions to or manipulations of painting media by the artist. Technical imaging was carried out using UVF to visualize the extent of Séraphine's use of natural resins. Analysis of the palette relied on XRF techniques and limited sampling for analysis by Raman and µ-FTIR spectroscopies. Overall, the following pigments were identified: lead white, zinc white, carbon-based black, red and brown ochres, umber, vermilion, alizarin lake, rhodamine B lake, Prussian blue, cobalt blue, ultramarine blue, chrome green, emerald green, viridian, cadmium yellow, and lead chromates, including chrome yellow deep and light, zinc yellow, and chrome orange. THM-Py-GCMS analysis of selected samples supported the documentary evidence of Séraphine's use of household oil paints; a single instance of a cellulose nitrate enamel paint was additionally determined by µ-FTIR. The chromatographic analysis also indicated a natural plant resin in her varnishes, probably dammar in combination with pine resin. Overall, this material investigation, accompanied by the art historical record, better reveals the techniques of an experimental painter whose works have come to epitomize French outsider artists of the early twentieth century.

Polystyrene microplastics enhance oxidative dissolution but suppress the aquatic acute toxicity of a commercial cadmium yellow pigment under simulated irradiation

Commercial cadmium yellow (CdS) pigment widely coexist with microplastics (MPs) in surface water, thus it is important to understand how MPs affect CdS pigment stability and toxicity under irradiation. Herein, the dissolution of CdS pigment (krelease = 0.118 h–1) under irradiation was visibly increased to 0.144 h–1 by polystyrene (PS) MPs, due to reactive species generation such as 1O2, •OH and 3PS* , while O2•− was unimportant to this process. The O2, humic acid, photoaging status of PS MPs could promote PS MPs-related CdS pigment dissolution rate by modifying reactive species generation. However, the CO32−, PO43− and alkaline condition significantly decreased the dissolution rate to 0.091, 0.053 and 0.094 h–1, respectively, through modifying free Cd2+ stability. Comparably, PS MPs-related CdS pigment dissolution was relatively slow in natural water samples (krelease = 0.075 h–1). PS MPs at environmental concentration can also promote CdS pigment dissolution and Cd2+ release, but suppress acute toxicity of CdS pigment to zebrafish larvae as increasing 10 h survival from 65% to 85% by adsorbing the Cd2+ and decreasing Cd2+ bioavailability. This study emphasized the environmental risks and human safety of CdS pigment should be carefully evaluated in the presence of PS MPs in aquatic environments.

Characterization and Degradation Analysis of Pigments in Paintings by Martiros Sarian: Attenuated Total Reflection Fourier Transform Infrared Spectroscopic Imaging and X-ray Fluorescence Approach

This paper presents a preliminary scientific investigation of pigments used by Martiros Sarian, a prominent Armenian artist known for his vibrant and evocative paintings. The study focuses on five of Sarian’s paintings from different periods of his career, namely, Morning in Stavrino, Arabian Dancer, Caravan, Yerevan Zangu River, and Kirovakan, dated between 1909 and 1948. Non-destructive techniques, including micro-attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging and X-ray fluorescence (XRF), were employed to characterize the pigments in the samples extracted from these paintings. The results reveal the presence of various pigments, including ultramarine blue, cobalt blue, cobalt cerulean blue, viridian, emerald green, cobalt green, celadonite green, cadmium yellow, chrome yellow, Venetian red, yellow ochre, red ochre, lead white, zinc white, and calcium carbonate. Additionally, metal carboxylates and oxalates, degradation products associated with the paint layers, were observed and discussed. The findings contribute to a better understanding of Sarian’s artistic technique and provide valuable insights for the conservation and restoration of his artworks.

A Visual Exchange of Everyday History, a Creative Exploration to Build Contextual Awareness within Parallel Learning Communities

This practitioner interview captures and analyses dialogue between two academic staff at different higher education institutions in the United Kingdom (UK), as a trial project to identify contemporary relationships with textile design history and contemporary culture. The project was established with the ambition to identify new strategies for student community learning in relation to contextual studies. The separate, but similar, lecture series the two academics present at their respective institutions aim to introduce design styles from 1900 to 2000, evolved from one programme devised when the two academics previously worked together. The project was developed through discussions concerning post-pandemic hybrid teaching and addressed concerns about the often-passive response to theoretical content and the challenge of developing a narrative that reflects the plurality of textile design histories as multiple cultural histories rather than one linear trajectory. By identifying topics arising in the lectures in their own everyday lives and locations, the two academics considered ways in which the students could be encouraged to make stronger connections for themselves with political and cultural discussions, to build greater critical skills and awareness. Inspired by Berger and Christie’s (1999), “I Send You This Cadmium Red: A Correspondence,” but with digital correspondence replacing letters in the post, the task was to seek out contemporary images that would narrate an element from each design history lecture, connecting heritage with the modern day. Building a shared digital image and narrative as the lecture series progressed, the exchanges inspired each academic to see the link to history from the correspondent’s viewpoint, while suggesting alternative ways of addressing the task in future weeks. The challenge proved to be invigorating and stimulating, establishing new pedagogy to integrating the past and present. The project and insights articulated through this article provide a model for shared academic practice that could be conducted over a longer timeframe or expanded to a larger collaborative group context. Both options provide collegiate support for individual curricular transformation and contribute towards enhancement surrounding decolonising the curriculum.

Material and Technical Analysis of La Inmaculada by Francisco Pacheco

Francisco Pacheco (1564–1644) was one of the most important Spanish painters, the author of the famous treatise Art of Painting, and a founder of Seville art school. His painting La Inmaculada (1610) forms part of the important art collection in the Archbishop’s Palace in Seville and represents the first realization of a new iconography, established by Pacheco. Later, he carried out several paintings with the same subject which are today in different collections. As part of a larger project, La Inmaculada was recently restored and analysed. The characterization of materials and painting procedures was carried out applying noninvasive in situ analysis by ultraviolet fluorescence (UVF), infrared reflectography (IRR), and X-ray fluorescence spectrometry (XRF). Results revealed many retouches, probably from different periods, as well as some pentimenti in the composition. Chemical analysis indicates a preparation made of Seville clay, lead white and some calcite on an animal glue layer, according to Pacheco’s own treatise, and a corresponding pigment palette for the 17th century: lead white, yellow and red earths, lead–tin yellow, vermilion, azurite, smalt, a copper-based green, umber, and bone black. Furthermore, modern pigments such as titanium and zinc whites, chrome green, and cadmium yellow were also identified as results of later interventions.

Lead Carboxylates and Chromatic Parameter Changes in Oil-Based Paintings Exposed to Volatile Organic Compounds

Some of the main concerns when attempting to preserve artwork regard environmental factors, such as luminosity, temperature and, recently, even atmospheric pollution. From this perspective, volatile organic compounds (VOC) stand out due to the wide availability of contaminating sources in internal museum environments. Amongst artistic objects susceptible to VOC interference, paintings are more likely to undergo it because their stability is closely related to each component. Thus, it is crucial to comprehend the interaction between VOC and paintings, specifically those with inorganic and adhesive pigments, and evaluate changes in chromatic parameters and the formation of metallic carboxylates. Mock-ups of paintings were prepared with cadmium yellow, chromium oxide, ultramarine blue, linseed oil, and lead white or gypsum primer. Exposure was arranged within an airtight container containing a VOC-saturated atmosphere: formaldehyde, acetic acid, hexanal and 2-butanone oxime. Color alteration occurred for ultramarine blue (greenish coloration) and cadmium yellow (lost luminosity). Infrared analysis showed the formation of lead carboxylates (acetate, formate and hexanoate) in all pigments. Micrographs of ultramarine models, verified via scanning electron microscopy, showed that an otherwise flat and homogenous appearance replaced the granular aspect of the paint; the flat regions being indicative of carboxylate formation.

Exploring the private universe of Henri Matisse in The Red Studio

The exhibition Matisse: The Red Studio allowed for an in-depth study of The Red Studio (1911) and six of the works featured in the painting by Henri Matisse (1869–1954) of his studio in Issy-les-Moulineaux near Paris. The grouping includes three paintings from the collection of the Statens Museum for Kunst (Le Luxe II, 1907, Nude with White Scarf, c. 1909, and Bathers, c. 1909), one painting from the collection of The Metropolitan Museum of Art (Young Sailor II, 1906), a painting from a private collection (Cyclamen, c. 1911), and a glazed and hand-painted earthenware plate from the collection of the Museum of Modern Art (Untitled (Female Nude), 1907). The six paintings were investigated using technical (X-radiography, ultraviolet-induced fluorescence, infrared reflectography) and chemical imaging (MA-XRF) and, in some cases, spectroscopic techniques (FORS, SEM–EDS, Raman, SERS, and μ-FTIR), to better elucidate Matisse’s materials and working techniques for this selection of paintings; the plate was also analyzed using MA-XRF. New findings revealed the full extent to which Matisse had completed The Red Studio before applying its hallmark color, referred to as Venetian red in his correspondence, over the original palette of blue, pink, and ochre that dominated the composition. Particular attention was given to identifying the wide range of pigment choices made by Matisse in the execution of the works from 1906 and 1911 that are depicted in The Red Studio. These pigments include lead white, zinc white, bone black, earth reds, madder lake, carmine lake, vermilion, cadmium yellow, yellow ochre, aureolin (cobalt) yellow, orpiment, viridian green, chromium-oxide green, cobalt blue, ultramarine blue, Prussian blue, cobalt violet (deep and light), and other cobalt violets, as well as possibly manganese violet and eosin red lake. The results of these analyses allowed for a direct comparison between the original works and their depictions and revealed that Matisse, unsurprisingly given his strong association with color, often translated the pigment choices faithfully between the actual works and their depictions in The Red Studio.

“Foundations of a great metaphysical style”: unraveling Giorgio de Chirico’s early palette

Properly situating Giorgio de Chirico’s metaphysical works within his lifetime is complicated due to incomplete provenances, his practice of deliberately falsifying dates, and the known existence of forgeries. De Chirico’s palette may have altered over time, due to shifts in his personal taste, changes in availability of materials, and innovations in paints; elucidating his palette and variations thereof during his metaphysical period (1911–1919) offers analytical insights that complement traditional connoisseurship when attempting to correctly position a given work within his lifetime. To this end, eleven paintings from his metaphysical period, and two in his metaphysical style but painted in the 1940s and backdated to the 1910s, were analyzed by non-destructive portable X-ray fluorescence spectroscopy. Analysis of some works was further complemented with micro-destructive analysis by scanning electron microscopy coupled with energy dispersive x-ray spectrometry, as well as Raman and Fourier transform infrared spectroscopy. While the grounds of his paintings are variable, his metaphysical palette is consistent and includes: lead white, zinc white, ochres and umbers, magnetite, bone or ivory black, vermilion, chrome yellow, Naples yellow, copper acetoarsenite, chromium oxide green, and Prussian blue. Less commonly used pigments include cerulean blue and cadmium yellow, and the backdated paintings lack lead white and vermilion.

Evolution of Liu Kang’s Palette and Painting Practice for the Execution of Female Nude Paintings: The Analytical Investigation of a Genre

The comprehensive technical investigation of female nude paintings by the Singapore pioneer artist Liu Kang (1911–2004) provided the evidence for a discussion of the evolution of his palette of colours and his working process for expression in this genre, particularly the execution of female bodies. As the artist’s free expression in classical nude paintings was limited by the censorship imposed by the Singapore government, the investigated artworks span two periods, 1927–1954 (early career) and 1992–1999 (the “golden years”, during which censorship policies were relaxed). Hence, eight paintings from the Liu family and National Gallery Singapore were selected for non- and micro-invasive analyses of the paint layers. The obtained results were supplemented with archival sources to elucidate certain aspects of Liu Kang’s working practice. The investigation revealed the importance of drawing and sketching studies in the development of artistic ideas. The analytical techniques, such as polarised light microscopy (PLM), field emission scanning electron microscope with energy dispersive spectroscopy (FE-SEM-EDS) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), enabled us to observe a transition from the yellow iron-based tonal ranges of skin colours to complex pigment mixtures composed of additions of cobalt blue, ultramarine, Prussian blue, Cr-containing yellow(s) and green(s), cadmium yellow, orange and/or red and organic reds, revealing the artist’s more liberal use of colours and his experimentation with their contrasting and complementary juxtaposes. In terms of painting technique, the artist’s comparatively laborious paint application using small brushes quickly gave way to a more effortless manipulation of the paint using bigger brushes and the incorporation of palette knives. Moreover, visible light (VIS), near-infrared (NIR) and X-ray radiography (XRR) imaging techniques led to the discovery of a hidden composition in one investigated artwork, which bears resemblance to the nude painting known only from an archival photograph. Additionally, for the first time, the archival search provided photographic evidence that Liu Kang used oil paint tubes from Royal Talens and Rowney in the 1990s. Overall, this in-depth investigation contributes to the understanding of Liu Kang’s approach to the female nude painting and may assist conservators and art historians in studies of twentieth-century commercial paints.

Deeper insights into the photoluminescence properties and (photo)chemical reactivity of cadmium red (CdS1\u2212xSex) paints in renowned twentieth century paintings by state-of-the-art investigations at multiple length scales

Cadmium red is the name used for denoting a class of twentieth century artists’ pigments described by the general formula CdS1−xSex. For their vibrant hues and excellent covering power, a number of renowned modern and contemporary painters, including Jackson Pollock, often used cadmium reds. As direct band gap semiconductors, CdS1−xSex compounds undergo direct radiative recombination (with emissions from the green to orange region) and radiative deactivation from intragap trapping states due to crystal defects, which give rise to two peculiar red-NIR emissions, known as deep level emissions (DLEs). The positions of the DLEs mainly depend on the Se content of CdS1−xSex; thus, photoluminescence and diffuse reflectance vis–NIR spectroscopy have been profitably used for the non-invasive identification of different cadmium red varieties in artworks over the last decade. Systematic knowledge is however currently lacking on what are the parameters related to intrinsic crystal defects of CdS1−xSex and environmental factors influencing the spectral properties of DLEs as well as on the overall (photo)chemical reactivity of cadmium reds in paint matrixes. Here, we present the application of a novel multi-length scale and multi-method approach to deepen insights into the photoluminescence properties and (photo)chemical reactivity of cadmium reds in oil paintings by combining both well established and new non-invasive/non-destructive analytical techniques, including macro-scale vis–NIR and vibrational spectroscopies and micro-/nano-scale advanced electron microscopy mapping and X-ray methods employing synchrotron radiation and conventional sources. Macro-scale vis–NIR spectroscopy data obtained from the in situ non-invasive analysis of nine masterpieces by Gerardo Dottori, Jackson Pollock and Nicolas de Staël allowed classifying the CdS1−xSex-paints in three groups, according to the relative intensity of the two DLE bands. These outcomes, combined with results from micro-/nano-scale electron microscopy mapping and X-ray analysis of a set of CdS1−xSex powders and artificially aged paint mock-ups, indicated that the relative intensity of DLEs is not affected by the morphology, microstructure and local atomic environment of the pigment particles but it is influenced by the presence of moisture. Furthermore, the extensive study of artificially aged oil paint mock-ups permitted us to provide first evidence of the tendency of cadmium reds toward photo-degradation and to establish that the conversion of CdS1−xSex to CdSO4 and/or oxalates is triggered by the oil binding medium and moisture level and depends on the Se content. Based on these findings, we could interpret the localized presence of CdSO4 and cadmium oxalate as alteration products of the original cadmium red paints in two paintings by Pollock.Graphical abstract

The influence of colouring materials and artificial ageing on the occurrence of nonspecific peptides in protein binders

The aim of this work was to identify the influence of selected pigments and artificial ageing on the occurrence of nonspecific peptides in protein binders used in artworks. For this purpose, two groups of pigments – inorganic (cadmium yellow, chalk, and ochre) and organic (indigo, carmine, and madder lake) were selected. The model samples containing protein binders (casein binder, gelatine, yolk and whole egg binder) mixed with the indicated pigments in final concentration of 1 % were exposed to the conditions causing accelerated ageing (UV light, higher temperature and relative humidity).The samples were analysed using two mass spectrometry techniques – LC-ESI-Q-TOF MS (Liquid Chromatography-Electrospray Ionization-Quadrupole-Time of Flight Mass Spectrometry) and MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry). The results from LC-ESI-Q-TOF MS were searched for sites where nonspecific cleavage of proteins occurred and for types and the number of modifications. MALDI-TOF MS data were subjected to the Principal Component Analysis (PCA).Beside amino acid modifications and spatial conformations another way of protein binder deterioration was described in this paper. It was found that pigments can influence the number of nonspecific peptide fragments and may thus led to binder degradation, or have a stabilizing effect. The data obtained from artificial ageing show that ageing may also affect the occurrence of nonspecific peptides and, that this effect strongly depends on the presence of the specific pigment or dye.

Environmentally benign rare earth pigments: effect of calcium dopant and tuning of bandgaps for different color hues

PurposeAs there is a strong inducement to develop new colored inorganic materials to substitute the current industrial pigments that are based on toxic metals hazardous to health and the environment, the purpose of this paper is to invent environmentally benign rare earth-based colorants as viable alternatives to the traditional toxic pigment formulations. Herein, the authors developed a series of rare earth pigments having the general formula Ca0.1 Ln0.9 PO4 ( Ln = Y , Pr , mixed rare earth oxides, RE and Di). After studying all the optical properties, the authors have gone for some coloring application in plastic like PMMA.Design/methodology/approachThe designed pigments were synthesized by traditional solid-state method. Stoichiometric amounts of each reagent were mixed in an agate mortar and the mixtures were calcined at optimized temperature 1000 °C for 4 h in electric furnace followed by auto–cooling. The samples were characterized by X-ray diffraction diffraction, UV–vis spectroscopy, scanning electron microscope (SEM), particle size distribution, color coordinates determination, acid/alkali test, thermo gravimetric (TG) analysis and CIE–1976 L*a*b* color scales. Among the various lanthanide ions and calcium ion as dopant, the pigment composition shows various hues ranges from green to yellow. The designed pigments consist of non–toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates like PMMA.FindingsThe present investigations establish that various color hues can be achieved by the incorporation of suitable chromophore metal ions like calcium in various rare earth host lattice by tuning of the band gaps. The coloring mechanism is based on the strong absorption of the pigments in the blue and red regions due to electronic transitions of the micro states of rare earth ion. The pigment composition shows various hues ranges from green to yellow. The coloring mechanism is based on the tuning of band gap by the dopant like calcium in various rare earth host lattice. In addition, this pigment was chemically and thermally stable. Finally, it has applied in plastics like PMMA.Research limitations/implicationsMechanism of the color appearance using band calculations and on possible applications of rare earth phosphate powders as pigments in plastics and paints have not been explored much. However, the properties of the Ca-doped rare earth phosphate implies that this material has a potential to be applied as a satisfactory pigment for coating or coloring except for glaze, which may cause a side reaction at high temperatures, especially taking into consideration the economics and ecologies. The possibility of Ca2+ incorporation in CePO4 with monazite structure-type has been established.Practical implicationsThe designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.Social implicationsThere is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. The designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.Originality/valueThere is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. So, the authors have developed new class of inorganic pigments that are both non-toxic and environmentally unimpeachable, while preserving or even exceeding the optical, thermal and chemical characteristics of the existing commercial pigments. The developed colorants find practical applications in polymer matrix like PMMA.

Microanalyses and Spectroscopic Techniques for the Identification of Pigments and Pictorial Materials in Monet's Pink Water Lilies Painting.

In this work, the technique and the pictorial materials employed by Claude Monet in Pink Water Lilies, presently housed at the National Gallery of Modern and Contemporary Art in Rome, were investigated. The painting underwent noninvasive investigations such as energy-dispersive X-ray fluorescence and visible reflectance spectroscopies. The combined use of these techniques allowed us to identify most of the inorganic pigments such as cobalt blue and violet, zinc oxide, cadmium yellow, vermilion, and mixtures. Particularly, the spectrophotometric curves allow for the detection of the anhydrous and hydrated chromium greens. Two micro-fragments of the painting were also examined with micro-Fourier transform infrared spectroscopy and the cross-sections obtained were analyzed with the optical microscope and with scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). Fourier Transform Infrared spectroscopy analyses allowed us to recognize the animal glue used for priming the canvas, which was covered with a ground layer consisting of calcite and lead white mixed with an oil binder. A lipidic binder was also detected in the color layer. Optical microscopy and SEM-EDS were useful to retrieve information about the stratigraphy, the distribution of pigments, and a more complete palette identification of phosphate, arsenate, and magnesium arsenate cobalt violets, and the red lake was possible.

CORRELATION STUDIES OF INDIGENOUS BIOFILM FORMING BACTERIA FOR RESISTANCE AGAINST SELECTED METALS, ANTIBIOTICS AND DYES DEGRADATION

This study determines correlation of biofilm-forming bacteria for selected metals, antibiotics and dyes. Total 12 strains having biofilm production potential were targeted in this study. Majority of them were Gram negative excluding MB377 and MB378, and facultative anaerobes. Isolates were mesophilic and exhibited growth capacity over a wide variety of pHs. Almost all isolates conferred resistance capacity against a wide range of multiple antibiotics having 0.0063 MAR for bacitracin, ampicillin, clindamycin, amoxicillin and sulphamethoxazole. Bacterial isolates displayed tolerance to diverse variety of metals i.e. cadmium, lead and iron 1000 mg L-1, copper 600-1000 mg L-1, chromium 700-1000 mg L-1 and nickel 200-600 mg L-1. Maximum heavy metal tolerance of 0.033 was observed for all metals excluding nickel. Correlation among metal tolerance and antibiotic resistance was extremely significant for chromium and bacitracin 0.862. Furthermore, moderate relationship (r= 0.682) between copper resistance and Basic Green 4 dye degradation was observed. Correlation coefficient for cadmium and Acid Red 2 dye was recorded as 0.512, while that for bacitracin and Basic Green 4 was noted as 0.665. These correlations proposed that resistance conferring genes might be present on same locus, genetic elements, chromosome or on a plasmid. 16S rRNA sequenced isolates were identified to be Klebsiella pneumoniae MB375, Staphylococcus sp. MB377, Klebsiella oxytoca MB381, Klebsiella pneumoniae MB394 and Klebsiella pneumoniae MB398. Potential of these biofilm forming strains to thrive under stressed environmental conditions proves them good entrants for being used in bioremoval of polluted sites after further studies on their metabolic pathways.

Complex Relationships: A Materials Study of Édouard Vuillard’s Interior, Mother and Sister of the Artist

Édouard Vuillard (1868–1949) is well known for his small atmospheric paintings, often portraying his own home and family as the subject matter. Interior, Mother and Sister of the Artist (1893) underwent at least one restoration treatment before being acquired by the Museum of Modern Art (MoMA) in 1934. The painting was treated again in 1954, but no analysis was carried out to understand the artist’s methods and materials at that time. To better understand the choices of Vuillard in Interior, Mother and Sister of the Artist, a comprehensive suite of imaging and spectroscopic analyses was undertaken, including: XRR, UVF and IRR Photography, XRF, Raman spectroscopy and SERS, and µ-FTIR. Statistical analysis on the XRF data using MCR-ALS further revealed some of the intricacies of Vuillard’s technique and color choices, where a large number of pigments were used in designing this intimate composition, including lead white, zinc white, bone black, ochre, umber, vermilion, Geranium lake, red lead, ultramarine, Prussian blue, chrome yellow, chrome orange, zinc yellow, strontium yellow, cadmium yellow, and a chromium oxide green.

The influence of light and relative humidity on the formation of epsomite in cadmium yellow and French ultramarine modern oil paints

The effect of relative humidity (RH) and light on the development of epsomite (MgSO4·7H2O) in Winsor & Newton cadmium yellow (CY) and French ultramarine (FU) artists’ oil colour paints was investigated. Tube paint samples were aged for 12 weeks at either 50% or 75% RH, under ambient light (200 ± 1 lx), elevated light (11,807 ± 328 lx), and near-dark conditions. Aged paint samples were characterised using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results indicated that ageing at 75% RH in elevated light conditions, promoted the formation of hydrated magnesium sulphate (MgSO4·6–7H2O) crystals on the surface of both paints. The formation of sodium sulphate (Na2SO4) as a degradation product of French ultramarine oil paints after ageing at 75% RH in elevated light conditions is described. The formation of magnesium sulphate crystals in the absence of elevated SO2 is a new finding. For both cadmium yellow and French ultramarine oil paints, the pigments present are a likely source of sulphur, enabling the formation of sulphate salts, i.e., cadmium sulphide (CdS) yellow, and the sulphur radical anions (S3−) present in ultramarine pigment. Sulphur-containing impurities arising from pigment manufacture are an additional possibility. It was previously theorised that epsomite formation in water-sensitive twentieth century oil paintings resulted from exposure to the elevated atmospheric sulphur dioxide (SO2) levels of the 1950s–1970s. This study demonstrates that hydromagnesite-containing cadmium yellow and French ultramarine oil paints of any period may be vulnerable to water-soluble sulphate salts formation and that this process is promoted by exposure to light and high (75%) RH environments. The formation of sulphate salts as a degradation product is known to contribute toward the development of water sensitivity of modern oil paintings which can pose significant challenges to conservation. Therefore this study highlights the importance of minimising exposure to light and raised relative humidity for paintings containing such CY and FU oil paint passages, to help slow down these types of degradation phenomena which have implications for preservation.

Exploring Liu Kang’s Paris Practice (1929–1932): Insight into Painting Materials and Technique

This paper presents the results of an extensive study of 14 paintings by the pioneering Singapore artist Liu Kang (1911–2004). The paintings are from the National Gallery Singapore and Liu family collections. The aim of the study is to elucidate the painting technique and materials from the artist’s early oeuvre, Paris, spanning the period from 1929 to 1932. The artworks were studied with a wide array of non- and micro-invasive analytical techniques, supplemented with the historical information derived from the Liu family archives and contemporary colourmen catalogues. The results showed that the artist was able to create compositions with a limited colour palette and had a preferential use of commercially available ultramarine, viridian, chrome yellow, iron oxides, organic reds, lead white, and bone black bound in oil that was highlighted. This study identified other minor pigments that appeared as hue modifications or were used sporadically, such as cobalt blue, Prussian blue, emerald green, cadmium yellow, cobalt yellow, and zinc white. With regard to the painting technique, the artist explored different styles and demonstrated a continuous development of his brushwork and was undoubtedly influenced by Modernists’ artworks. This comprehensive technical study of Liu Kang’s paintings from the Paris phase may assist art historians and conservators in the evaluation of the artist’s early career and aid conservation diagnostics and treatment of his artworks. Furthermore, the identified painting materials can be compared with those used by other artists active in Paris during the same period.

Formation of zinc oxalate from zinc white in various oil binding media: the influence of atmospheric carbon dioxide by reaction with 13CO2

The formation of metal oxalates in paintings has recently gained a great deal of interest within the field of heritage science as several types of oxalate compounds have been identified in oil paintings. The present work investigates the formation of metal oxalates in linseed oil in the presence of the artists’ pigments zinc white, calcite, lead white, zinc yellow, chrome yellow, cadmium yellow, cobalt violet, and verdigris. The oil paint films were artificially photo-aged by exposure to UVA light at low and high relative humidity, and afterwards analysed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The results showed that, compared to the other pigments investigated, zinc white is especially prone to metal oxalate formation and that high humidity is a crucial factor in this process. Consequently, the reactivity and photo-aging of ZnO in various oil binding media was investigated further under simulated solar radiation and at high relative humidity levels. ATR-FTIR showed that zinc oxalate is formed in all oil binding media while X-ray powder diffraction (PXRD) revealed it was mainly present in an amorphous state. To examine whether atmospheric CO2(g) has any influence on the formation of zinc oxalate, experiments with isotopically enriched 13CO2(g) were performed. Based on ATR-FTIR measurements, neither Zn13C2O4 nor Zn13CO3 were formed which suggests that the carbon source for the oxalate formation is most likely the paint itself (and its oil component) and not the surrounding atmosphere.