The materials of six Karen textiles from the British Museum's collection were investigated with t... more The materials of six Karen textiles from the British Museum's collection were investigated with the main aim of studying the production changes over the course of the nineteenth century and how these changes related to local and colonial trade networks. The textiles span chronologically from the 1830s to the early 1900s according to their attribution dates, and include traditional garments such as tunics and skirts, in addition to representing a broad colour palette and different dyeing and weaving techniques. The investigation was conducted non-invasively by using digital microscopy, broadband multispectral imaging (MSI) and fibre optic reflectance spectroscopy (FORS). The results guided a sampling campaign during which samples were taken and investigated by optical microscopy (OM), scanning electron microscopy energy dispersive X-ray spectrometry (SEM-EDX) and high-performance liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). Local natural dyes, such as red and yellow from Morinda citrifolia, lac dye (Kerria lacca), gamboge (Garcinia sp.), turmeric (Curcuma longa), indigo and tannins were found in the older textiles, supporting a possible early production, whereas mixtures of natural and synthetic dyes, including synthetic alizarin (CI 58000), rhodamine B (CI 45170), orange I (CI 14600), diamond green B (CI 42000), diamond green G (CI 42040), auramine O (CI 41000), naphthol yellow S (CI 10316), chrysamine G (CI 22250), crystal violet (CI 42555) and Pigment Red 53:1 (CI 15585:1) were identified in the later textiles. Observations on mordants revealed the use of aluminium, tin and chrome, whereas fibre characterisation highlighted the use not only of cotton (Gossypium sp.) but also of felted wool imported from Europe and Chinese silk dyed with the Chinese cork tree (Phellodendron chinense) yellow dye. The results draw an interesting picture of the introduction of new dyeing materials and techniques in Myanmar over the nineteenth century, and how these impacted the production of traditional Karen textiles.
In the framework of the 'Amorepacific Project for the conservation of Korean pictorial art' (2018... more In the framework of the 'Amorepacific Project for the conservation of Korean pictorial art' (2018-2023) at the British Museum, three traditional Korean paintings have been investigated with the aim of supporting their conservation and obtaining information about the dyes used in the mounting textiles and other mounting elements. The paintings include a rare example of late 18thcentury traditional Korean portraiture (accession number 1996,0329,0.1); a late 19th-century twopanel screen silk painting of Pyeongsaeng-do-Scenes of life (accession number 2016,3028.1); and a late 19th-century twelve-panel screen silk painting representing the Five Confucian virtues (accession number 1957,1214,0.1). The mounting textiles were investigated non-invasively by using digital microscopy and fibre optic reflectance spectroscopy (FORS), and the results guided a minimally invasive sampling campaign. Fourteen samples were analysed by using high-pressure liquid chromatography coupled with diode array and tandem mass spectrometry detectors (HPLC-DAD-MS/MS), leading to the identification of the natural dyes indigo, sappanwood (Biancaea sappan, formerly Caesalpinia sappan), amur cork tree (Phellodendron amurense) and safflower (Carthamus tinctorius) in the mounting elements of the 18th-century portrait. These results confirmed some of the non-invasive observations and were in agreement with the production date of the painting. Both natural and synthetic dyes were identified in the mounting textiles of the panel screens. Among the synthetic dyes, fuchsin (C.I. 42510), methyl violet 3B (C.I. 42536), methyl blue (C.I. 42780) and benzopurpurin 4B (C.I. 23500) were identified. These are early synthetic dyes first synthesised between the 1860s and the 1880s, suggesting that the silk textiles are likely to have been dyed in the last part of the 19th century.
Natural dyes have a millenary history of tradition, which began with the instinctive human desire... more Natural dyes have a millenary history of tradition, which began with the instinctive human desire to reproduce colours of its surroundings and applying them to a surface. Colour is intrinsically related to the very concept of art and, prior to the invention of synthetic colourants in 1856, people drew from the natural world to obtain colouring substances.
Scientific analyses of the traditional materials and methods in thangka production are uncommon, ... more Scientific analyses of the traditional materials and methods in thangka production are uncommon, as thangkas are sacred objects, the sampling of which is discouraged, in order to preserve their integrity. This study builds on this important ethical challenge and presents a three-stage methodology that systematically delves deeper into each layer of the composition, successfully enabling the investigation of different phases of production. In the first stage, visual examination of the painting, including observations under magnification, was used to assess its condition. In the next step, the infrared reflected (IRR) and shortwave infrared (SWIR) images revealed the underdrawing and instances of modifications as well as colour notations. Additionally, ultraviolet-induced visible luminescence (UVL), infrared-reflected false colour (IRRFC) and X-ray images provided important preliminary information on the colourants present, the nature of the underdrawing, and the painting technique. In the final stages, fibre optic reflectance (FORS), Fourier-transform infrared (FTIR) and Raman spectroscopies confirmed the identity of many of the pigments (cinnabar/vermillion, minium, iron oxide, malachite, azurite, indigo, Indian lac), the ground and the binder used for the blue and green paint layers. In addition, key details of practices and materials were revealed, that may indicate provenance or other information of scholarly importance. These will constitute a helpful comparison to existing and future studies of other thangkas.
Enredos are iconic textiles that have been produced for centuries by Mexican communities to celeb... more Enredos are iconic textiles that have been produced for centuries by Mexican communities to celebrate pregnancy,
weddings, etc. They have been traditionally dyed with three natural dyes, namely indigo, cochineal, and
shellfish purple. In this study two modern enredos produced in the 1980s, now in the collection of the National
Museum of Mexican Art, were investigated with the aim of understanding the colorants used and informing on
the use of traditional dyeing practices in modern Oaxaca.
The results were obtained by a combination of non-invasive analytical techniques, namely reflectance imaging
spectroscopy (RIS) and macro X-ray fluorescence (MA-XRF), and high pressure liquid chromatography coupled to
diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). In addition to representing the first
example of this combination of techniques applied to the study of textiles, this study also reports on the first
characterization of the purple dye extracted from the Plicopurpura pansa G. mollusk by HPLC-DAD-MS/MS.
Moreover, this study reveals the simultaneous use of synthetic red dyes with naturally-derived colorants such
as indigo and shellfish purple. The limitations of the various techniques to provide an ultimate identification of
certain dyes are emphasized together with the need for additional foundational research to expand molecular
databases for the identification of synthetic dyes. Nevertheless, the results shed light on a dynamic dyeing
scenario in modern Oaxaca (Mexico), in which traditional materials and methods are used alongside new ones in
an attempt to preserve meaningful local practices.
This paper presents the pigment characterization in six impressionist and post-impressionist pain... more This paper presents the pigment characterization in six impressionist and post-impressionist paintings by three leading Puerto Rican artists: Francisco Oller (1833–1917), José Cuchí y Arnau (1857–1925), and Ramón Frade (1875–1954).
The paintings, belonging to the Corporación de las Artes Musicales and Museo de Arte de Puerto Rico (San Juan, Puerto Rico), were investigated through a combination of complementary non- and micro-invasive scientific techniques.
The use of non-invasive macro-X-ray fluorescence (MA-XRF) and reflectance imaging spectroscopy (RIS) was applied for the first time to characterize Puerto Rican artists’ palette. The non-invasive approach was integrated with spectroscopic techniques such as Raman and/or Fourier-transform infrared (FTIR) spectroscopy, as well as high pressure liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS), when sampling was possible. While this technical investigation reveals pigments that are typical for late 19th/early twentieth century paintings, it also emphasizes some unexpected findings, including the use of cobalt green and synthetic yellow lakes, which enabled the date given to some of the paintings to be refined to post 1910 rather than their current dates of ca. 1890. This study confirms that the Puerto Rican artist’s palettes are very similar to their European
contemporaries, underscoring both their European training and their attempt to adapt these methods of painting to a new Caribbean identity emerging from the Spanish American War.
This study presents the results obtained during the optimization phase of a protocol based on imm... more This study presents the results obtained during the optimization phase of a protocol based on immunofluorescence microscopy (IFM) with the aim to characterize and localize proteins in fluid-rich samples of cultural heritage interest.
Chicken serum albumin from chicken blood was considered the primary target. Ovalbumin from chicken egg albumen (egg white) was also used as a common target protein to test the versatility of the protocol. Mock-ups were created, obtaining a complex distribution of the proteins in a porous matrix, thus providing a good approximation to a real case scenario. Thin sections of 1 µm thickness were then obtained using a cyanoacrylate-based tissue adhesive for the first time in samples of cultural heritage interest. Thin sections were preferred over standard cross sections, as they enabled multiple experiments to be performed by easily generating multiple sections from the same sample. This was particularly important during the optimization phase of the indirect immunochemical procedure, as the concentration of the blocking solutions, primary and secondary antibodies had to be optimized as well as the washing steps, time and temperature of incubation. The use of secondary antibodies conjugated with quantum dots fluorophores and the use of single wavelength structured illumination in the fluorescence microscope set-up reduced the contribution from unspecific fluorescence.
All these technical advances led to the enhanced mapping of the distribution of both ovalbumin and chicken serum albumin in the mock-up samples. The material distribution was also mapped using micro-reflectance imaging spectroscopy, which confirmed the localization of the target materials, thus laying the foundation for a multi-modal imaging protocol, which will be applied to samples taken from fluid-rich patinas on West African sculptures.
Mount components and textile borders represent important elements of Asian paintings. However, th... more Mount components and textile borders represent important elements of Asian paintings. However, they are often side-lined or not considered an integral part of the original piece, as they may be later additions or may have been replaced during historic conservation or mounting interventions. Nevertheless, evidence is sometimes present that textile borders are contemporaneous to the production of the paintings they frame or, in the case of paintings found in archaeological contexts, to the time of deposition. Even when not contemporaneous with the paintings, the mount textiles are often of significant historic interest in themselves, showing a range of complex textile techniques and materials, and highlighting the re-use of fabrics. In all these cases, the study and reconstruction of the original colours of the borders enable further understanding of the holistic visual impact originally intended for the composition, as well as of the role of colour itself, which was used to emphasise, complement or contrast important pictorial themes or motifs in the paintings. Furthermore, the identification of dyes and dyeing techniques has the potential to support the production date and provenance of the paintings. In this study, the textile borders and some additional mounting elements of six paintings (late 9th-10th century CE) from the Library Cave, Mogao Grottoes, Dunhuang, China, one rare Korean portrait painting dated 1789 CE, and two Tibetan thangkas (18th century) were investigated with the aim to identify the dyes present. Fibre optic reflectance spectroscopy (FORS) was used to obtain information non-invasively and, when sampling was possible, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to obtain molecular identification of the dyestuffs employed in their production. Typical Asian dyes, such as gromwell (Lithospermum erythrorhizon), sappanwood (Biancaea sappan), safflower (Carthamus tinctorius), turmeric (Curcuma longa) and pagoda tree flower buds (Sophora japonica), were identified. Some of the dyeing techniques were commensurate with the geographical and temporal provenance assigned to these pieces. Considerations about fading and discolouration of the dyes enabled valuable additional information to be obtained that complements the evidence gleaned from the study of the paintings and informs conservators and curators on best practices in the preservation and display of these precious and delicate artworks.
Commonly exhibited in museum galleries, animal mummies have been the focus of interest of both vi... more Commonly exhibited in museum galleries, animal mummies have been the focus of interest of both visitors and researchers alike. The study of these animal remains not only provides new insights into embalming techniques, but also brings a unique perspective on religious, social and economic practices. Twenty animal mummies are discussed in this study, including cats, ibises, crocodiles, calves and birds of prey from the collections of the British Museum (London, UK) and the Museo Egizio (Turin, Italy). The external textile wrappings encasing the mummified body of the animals were investigated with the main aim of identifying the colourants used. In fact, these are mostly patterned using undyed and coloured (mostly red, brown and black) linen strips. Broadband multispectral imaging (MSI) was initially carried out to obtain preliminary information at the macro-scale on the distribution and chemical nature of the colouring agents. Fibre optic reflectance spectroscopy (FORS) was then used to survey several coloured areas of the textile wrappings. Safflower (Carthamus tinctorius) and red ochre were identified non-invasively. Representative samples were then taken and observed using optical microscopy (OM) and scanning electron microscopy (SEM), in order to obtain information at the micro-scale on the distribution of the colouring agents on the fibres, as well as the presence of other materials, including those from environmental contamination. Energy dispersive X-ray spectrometry (EDX) revealed the elemental composition of particles and clear areas of the fibres, whereas high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) provided the identification of the organic dyes at a molecular level. The use of hydrolysable and condensed tannins, in combination with iron as a mordant, was found to be used in the very dark shades, which generally corresponded to the textiles with the worst state of preservation. Nevertheless, other aspects, such as fibre processing and bleaching, fungal attack and presence of coating materials appeared to play a role in the evaluation of the conservation state of these textiles. The characterisation of the dyes and the additional inorganic materials contributed to elucidating the production technology of the colours used for animal mummification, and provided insights into ancient dyeing methods.
In the past 30 years the study of the composition and chemistry of Asian lacquers has reached a h... more In the past 30 years the study of the composition and chemistry of Asian lacquers has reached a high level of interest among scientists and conservators. As a result, analytical strategies have been developed to characterise and identify these materials in complex samples, sometimes thousands of years old.
Asian lacquers are mainly composed of polymerised alkylcatechols and they are often applied in mixtures with several other organic and inorganic materials, such as oils, plant gums, mineral pigments, organic additives, etc. The polymeric nature of Asian lacquers limits the scientific approaches that can be used to investigate them. Technological progress and an increase in popularity of analytical pyrolysis (Py) have run parallel to the advancement of research in the field of Asian lacquer identification. With the ability to distinguish the different types of lacquers and to identify most of the other materials mixed with them, pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) is the most effective technique in this type of investigation. Several research groups have optimised analytical conditions, derivatisation steps and data treatment to create reliable protocols with wide applicability.
The information related to the development of such protocols is summarised in this review, together with some critical comparisons and suggestions on future perspectives in this research field.
This study focuses on the analysis of 61 samples taken from wool fabric specimens present in the ... more This study focuses on the analysis of 61 samples taken from wool fabric specimens present in the appendix of the book “A Manual of Dyeing: For the Use of Practical Dyers, Manufacturers, Students, and All Interested in the Art of Dyeing” by E. Knecht, C. Rawson and R. Loewenthal, published in England in 1893. This manual is a valuable source of information, as it partially describes the chemistry of the molecules used to dye the specimens. The dyes are presented with the common commercial names used at the end of the 19th century and the publication date ensures that they were all synthesized before 1893.
The first aim of the study was to explore the correspondence between the dyes described in the manual and the molecules actually present in the samples. High performance liquid chromatography coupled to diode array and mass spectrometric detectors (HPLC-DAD-MS) was used for the molecular characterization of the samples. The results were integrated with a thorough search of historic information on early synthetic dyes, to clarify the dye nomenclature, and ultimately the molecular structures of the detected molecules.
The results showed that the labels reported in the manual often do not correspond to the actual dyes present in the samples. In a number of cases, mixtures of dyes of different categories were actually used to obtain a certain color shade. We created a database of more than 160 molecules, including their UV–Vis absorption spectra and MS details, many of which are not reported in the scientific literature. This represents a valuable new comparative dataset useful for the identification of these molecules in historic samples.
Book: Analytical Strategies for Cultural Heritage Materials and their Degradation, 2021
Ceramics, stones, metallic objects, bones, leather, wood and textiles are among the most importan... more Ceramics, stones, metallic objects, bones, leather, wood and textiles are among the most important categories of archaeological remains. The information carried by these materials is often invaluable, as they represent precious and sometimes unique windows into past civilizations and into the evolution of humankind. Scientific research has the aim of selecting the most suitable analytical techniques in order to characterize these materials and retrieve the maximum amount of information possible without compromising the integrity of the objects. In a parallel way, conservation strategies have been extensively researched with the intention of preserving this precious archaeological evidence for future generations. However, both scientific and conservation research must first take into account the characteristics of the burial environments and their impact on the state of preservation of archaeological remains. This is particularly important for organic materials, as these are naturally degraded in most common conditions and are therefore relatively rare in archaeological findings. This chapter discusses the burial environments that permit the survival of archaeological materials, and also the implications that specific environmental agents have on the state of preservation of such materials. The analytical approaches used to scientifically investigate archaeological objects, assess their state of preservation and support conservation choices are also presented.
This review describes the capability of analytical pyrolysis-based techniques to provide
data on ... more This review describes the capability of analytical pyrolysis-based techniques to provide data on lignin composition and on the chemical alteration undergone by lignin in archaeological wooden objects. Applications of Direct Exposure Mass Spectrometry (DE-MS), Evolved Gas Analysis Mass Spectrometry (EGA-MS), and single and double-shot Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) in archaeological lignin characterisation are described. With comparison to cellulose and hemicelluloses, lignin is generally less prone to most degradation processes affecting archaeological artefacts in burial environments, especially waterlogged ones, which are the most favourable for wood preservation. Nevertheless, lignin also undergoes significant chemical changes. As wood from waterlogged environments is mainly composed of lignin, knowledge of its chemical structure and degradation pathways is fundamental for choosing preventive conservation conditions and for optimising consolidation methods and materials, which directly interact with the residual lignin. Analytical pyrolysis coupled with mass spectrometry, used in several complementary operational modes, can gather information regarding the chemical modifications and the state of preservation of lignin, especially concerning oxidation and depolymerisation phenomena. Several applications to the analysis of wood from archaeological artefacts affected by different conservation problems are presented to showcase the potential of analytical pyrolysis in various scenarios that can be encountered when investigating archaeological waterlogged wood.
Three Japanese woodblock prints from the Edo period (1603-1868) underwent a scientific investigat... more Three Japanese woodblock prints from the Edo period (1603-1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques. A multi-analytical approach was adopted, combining non-invasive techniques, such as fiber optic reflectance spectroscopy (FORS), Raman spectroscopy, multispectral imaging (MSI), and macro X-ray fluorescence (MA-XRF) with minimally invasive surface-enhanced Raman spectroscopy (SERS). The results enabled many of the pigments to be identified and their distribution to be studied, apart from two shades of purple of organic composition. Consequently, the potential of high-pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was explored for the first time with application to Japanese woodblock prints. The intrinsic sensitivity of the instrument and an effective extraction protocol allowed us to identify a mixture of dayflower (Commelina communis) blue and safflower (Carthamus tinctorius) red in purple samples constituted of 2-3 single fibers. In addition to the innovative integration of MA-XRF and HPLC-MS/MS to investigate these delicate artworks, the study concluded on the use of traditional sources of colors alongside newly introduced pigments in late Edo-period Japan. This information is extremely important for understanding the printing practices, as well as for making decisions about display, conservation, and preservation of such artworks. Japanese woodblock prints are among the most popular forms of artworks on paper. The prints usually depict ordinary elements of life, such as landscapes, tales from history, scenes from the Kabuki theatre, as well as courtesans, or geishas. Due to their low manufacture cost, woodblock prints were mass produced and widely distributed. In the Edo period (1603-1868 AD), Japanese prints became one of the dominant art movements. The vibrant colors and extremely various palette of nuances, as well as the particularly appealing style of this form of art, have not only attracted the eyes of collectors for centuries, but also continue to capture the attention of the general museum public. Nowadays, Japanese woodblock prints can be found in great numbers in many museum collections, including the Metropolitan Museum of Art's (New York City, USA).
A successful application of Er:YAG laser for the cleaning of a restored Assyrian relief sculpture... more A successful application of Er:YAG laser for the cleaning of a restored Assyrian relief sculpture from the British Museum collection is presented. Displayed in the gallery, the sculpture has darkened over time due to the natural deposition of dirt, in particular on restored parts. Since traditional cleaning methods have demonstrated to be unsuccessful, a scientific investigation was performed to identify the composition of the soiling and the materials used for the restoration. The analysis suggested the presence of gypsum, calcium oxalate, carbonates and alumino-silicates on the encrustation. The molded plaster, composed of lime and gypsum and pigmented aggregates, was likely prepared at the end of the 19th century to mimic the stone color. It was repainted with what was identified as a modern oil-based overpaint, applied to cover darkening during a second conservation treatment in the 20th century. Laser trials were first performed on small areas of the objects and on mock-ups to determine the critical fluence thresholds of the surface, investigated through visual examination and analyses using Fourier transform infrared spectroscopy (FTIR) and Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The right parameters and conditions to be used during the cleaning process were, therefore, determined. The chemical selectivity of the cleaning process allowed us to complete the treatment safely while preserving the restoration.
This study focuses on the dye analysis of 26 ikat textiles present in the collection of the Arthu... more This study focuses on the dye analysis of 26 ikat textiles present in the collection of the Arthur M. Sackler Gallery and originally collected by Dr. Guido Goldman with the aim to gain additional information about their provenance and dating. The investigation exploits the full potential of a multi-analytical approach, starting with a non-invasive survey of all the colors using fiber optic reflectance spectroscopy (FORS), which revealed the presence of indigo and insect-based red dyes. These data were used to select areas from which samples were taken and analyzed by high performance liquid chromatography diode array detector (HPLC-DAD). These results enabled most of the natural sources of dyes to be fully identified, including American cochineal (Dactylopius coccus), madder (probably Rubia tinctorum), lac (probably Kerria lacca), larkspur (Delphinum semibarbatum), pagoda tree flower buds (Sophora japonica), grape vine leaves (Vitis vinifera), indigo and tannins. Complex mixtures of dyes were present in most samples, as a result of both the ikat making process itself and traditional dyeing practices. Synthetic dyes were identified in 9 of the textiles. Samples were re-analyzed using HPLC-DAD coupled to mass spectrometry (HPLC-DAD-MS). Malachite green (basic green 4, C.I. 42000), fuchsine (basic violet 14, C.I. 42510), rhodamine B (basic violet 10, C.I. 45170) and methyl violet (basic violet 1, C.I. 42535) were identified, and a few other tentatively identified synthetic dyes (probably orange I, II and IV, rhodamine 6G, patent blue V and alizarin yellow GG) were detected. As the first synthesis of early synthetic dyes is well documented, their presence was used to refine the dating of these textiles. The contextualization of the results also appeared to support the stylistic assumption that more intricate and colorful designs with a higher level of complexity are dated earlier than simpler, larger and more graphic ones. The overall information acquired reveals a dynamic scenario and an interesting window into the dyers' experiments and adjustments to the economic and technological changes of the nineteenth century.
People in north-east Brazil mostly rely on fuelwood and charcoal for domestic energy consumption.... more People in north-east Brazil mostly rely on fuelwood and charcoal for domestic energy consumption. Traditionally, four local wood taxa (Mimosa tenuiflora, Mimosa ophthalmocentra, Croton sonderianus and Cenostigma pyramidale) from the caatinga have been selected for this purpose. As the final quality of charcoal is directly related to the charring conditions, as well as the chemical composition of the raw materials and the behaviour of the lignocellulosic matrix during the charring process, the aim of this study was to investigate how far differences in these parameters exert a major control on the charcoal formation, in order to give a molecular insight as to why these particular wood species might be preferred for high-quality charcoal in the perspective of sustainable management and harvesting regimes. Pyrolysis gas chromatography mass spectrometry (Py-GC-MS) and scanning electron microscopy (SEM) were used to study the chemical composition and anatomical changes of the wood samples before and after charring experiments were carried out at 400 and 600 °C. The charring conditions were also reproduced in the controlled environment of the pyrolysis chamber and evolved gas analysis mass spectrometry (EGA-MS) was used for the first time to monitor the evolution of the thermal degradation products. The thermal behaviour of the wood components was different compared to other wood taxa for which comparable data are available. These differences were partially related to the particular nature of the carbohydrate-lignin interactions, to a relatively low level of lignin condensation, and to the substantial presence of gums or resins, which formed charred deposits. These characteristics, often neglected in charcoal analysis, imply that the wood components (especially cellulose) are released more slowly during the charring process, and this translates into the ability of these wood species to retain the main features of their anatomical structure even when exposed to high temperature for a relatively long time. The anatomical alterations observed, such as the loss of the middle lamella, the disappearance of the pit membranes, and the homogenisation of cell walls are ultimately in agreement with the formation of a particularly recalcitrant carbonaceous matrix upon charring at relatively low temperature (400 °C for 2 hours). This study presents the first molecular characterisation of these wood species and some methodological advancement on the use of EGA analysis using isothermal conditions is provided. The role of carbohydrate-lignin interactions and non-lignocellulosic wood components in charcoal production is discussed and the importance of combining chemical data and anatomical observations in wood research is underlined.
Identification of Asian lacquers in museum objects is a challenging task. Their identification by... more Identification of Asian lacquers in museum objects is a challenging task. Their identification by mass spectrometry is based on molecular marker recognition, and analysis of chromatographic profiles of several types of molecules. A summary of published markers and chromatographic profiles ‒ obtained with and without thermally assisted reactions (silylation and methylation) ‒ is included in this paper. Based on this, a decision-making scheme was established, and proposed to guide data interpretation. This method of data analysis was then applied to a group of lacquered objects belonging to the Asian art collection of the Museum of Zaragoza (Spain). Based on stylistic and art historical information, the objects are dated from the 16th to the 20th century and attributed to Japanese, Chinese, Burmese and Thai manufacture. Analytical pyrolysis with in situ silylation - gas chromatography coupled with mass spectrometry (Py(HMDS)-GC/MS) was used to analyse the lacquers, and scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS) was used on cross sections to study the stratigraphy of the objects and understand the artistic techniques. The proposed scheme proved to be a useful analytical guide for the straightforward identification of the lacquer origin, even when this is present in mixture with other organic materials. In fact, a multi-faceted picture emerged, as some of the objects showed interesting mixtures of lacquers, such as urushi and thitsi, or unexpected compositions, which questioned their initial attributions. Complex or unexpectedly simple preparations and restoration treatments of the decorative surfaces were highlighted as well, supporting the museological investigation of these objects, in order to confirm/reject their authenticity and geographical provenance.
The materials of six Karen textiles from the British Museum's collection were investigated with t... more The materials of six Karen textiles from the British Museum's collection were investigated with the main aim of studying the production changes over the course of the nineteenth century and how these changes related to local and colonial trade networks. The textiles span chronologically from the 1830s to the early 1900s according to their attribution dates, and include traditional garments such as tunics and skirts, in addition to representing a broad colour palette and different dyeing and weaving techniques. The investigation was conducted non-invasively by using digital microscopy, broadband multispectral imaging (MSI) and fibre optic reflectance spectroscopy (FORS). The results guided a sampling campaign during which samples were taken and investigated by optical microscopy (OM), scanning electron microscopy energy dispersive X-ray spectrometry (SEM-EDX) and high-performance liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). Local natural dyes, such as red and yellow from Morinda citrifolia, lac dye (Kerria lacca), gamboge (Garcinia sp.), turmeric (Curcuma longa), indigo and tannins were found in the older textiles, supporting a possible early production, whereas mixtures of natural and synthetic dyes, including synthetic alizarin (CI 58000), rhodamine B (CI 45170), orange I (CI 14600), diamond green B (CI 42000), diamond green G (CI 42040), auramine O (CI 41000), naphthol yellow S (CI 10316), chrysamine G (CI 22250), crystal violet (CI 42555) and Pigment Red 53:1 (CI 15585:1) were identified in the later textiles. Observations on mordants revealed the use of aluminium, tin and chrome, whereas fibre characterisation highlighted the use not only of cotton (Gossypium sp.) but also of felted wool imported from Europe and Chinese silk dyed with the Chinese cork tree (Phellodendron chinense) yellow dye. The results draw an interesting picture of the introduction of new dyeing materials and techniques in Myanmar over the nineteenth century, and how these impacted the production of traditional Karen textiles.
In the framework of the 'Amorepacific Project for the conservation of Korean pictorial art' (2018... more In the framework of the 'Amorepacific Project for the conservation of Korean pictorial art' (2018-2023) at the British Museum, three traditional Korean paintings have been investigated with the aim of supporting their conservation and obtaining information about the dyes used in the mounting textiles and other mounting elements. The paintings include a rare example of late 18thcentury traditional Korean portraiture (accession number 1996,0329,0.1); a late 19th-century twopanel screen silk painting of Pyeongsaeng-do-Scenes of life (accession number 2016,3028.1); and a late 19th-century twelve-panel screen silk painting representing the Five Confucian virtues (accession number 1957,1214,0.1). The mounting textiles were investigated non-invasively by using digital microscopy and fibre optic reflectance spectroscopy (FORS), and the results guided a minimally invasive sampling campaign. Fourteen samples were analysed by using high-pressure liquid chromatography coupled with diode array and tandem mass spectrometry detectors (HPLC-DAD-MS/MS), leading to the identification of the natural dyes indigo, sappanwood (Biancaea sappan, formerly Caesalpinia sappan), amur cork tree (Phellodendron amurense) and safflower (Carthamus tinctorius) in the mounting elements of the 18th-century portrait. These results confirmed some of the non-invasive observations and were in agreement with the production date of the painting. Both natural and synthetic dyes were identified in the mounting textiles of the panel screens. Among the synthetic dyes, fuchsin (C.I. 42510), methyl violet 3B (C.I. 42536), methyl blue (C.I. 42780) and benzopurpurin 4B (C.I. 23500) were identified. These are early synthetic dyes first synthesised between the 1860s and the 1880s, suggesting that the silk textiles are likely to have been dyed in the last part of the 19th century.
Natural dyes have a millenary history of tradition, which began with the instinctive human desire... more Natural dyes have a millenary history of tradition, which began with the instinctive human desire to reproduce colours of its surroundings and applying them to a surface. Colour is intrinsically related to the very concept of art and, prior to the invention of synthetic colourants in 1856, people drew from the natural world to obtain colouring substances.
Scientific analyses of the traditional materials and methods in thangka production are uncommon, ... more Scientific analyses of the traditional materials and methods in thangka production are uncommon, as thangkas are sacred objects, the sampling of which is discouraged, in order to preserve their integrity. This study builds on this important ethical challenge and presents a three-stage methodology that systematically delves deeper into each layer of the composition, successfully enabling the investigation of different phases of production. In the first stage, visual examination of the painting, including observations under magnification, was used to assess its condition. In the next step, the infrared reflected (IRR) and shortwave infrared (SWIR) images revealed the underdrawing and instances of modifications as well as colour notations. Additionally, ultraviolet-induced visible luminescence (UVL), infrared-reflected false colour (IRRFC) and X-ray images provided important preliminary information on the colourants present, the nature of the underdrawing, and the painting technique. In the final stages, fibre optic reflectance (FORS), Fourier-transform infrared (FTIR) and Raman spectroscopies confirmed the identity of many of the pigments (cinnabar/vermillion, minium, iron oxide, malachite, azurite, indigo, Indian lac), the ground and the binder used for the blue and green paint layers. In addition, key details of practices and materials were revealed, that may indicate provenance or other information of scholarly importance. These will constitute a helpful comparison to existing and future studies of other thangkas.
Enredos are iconic textiles that have been produced for centuries by Mexican communities to celeb... more Enredos are iconic textiles that have been produced for centuries by Mexican communities to celebrate pregnancy,
weddings, etc. They have been traditionally dyed with three natural dyes, namely indigo, cochineal, and
shellfish purple. In this study two modern enredos produced in the 1980s, now in the collection of the National
Museum of Mexican Art, were investigated with the aim of understanding the colorants used and informing on
the use of traditional dyeing practices in modern Oaxaca.
The results were obtained by a combination of non-invasive analytical techniques, namely reflectance imaging
spectroscopy (RIS) and macro X-ray fluorescence (MA-XRF), and high pressure liquid chromatography coupled to
diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). In addition to representing the first
example of this combination of techniques applied to the study of textiles, this study also reports on the first
characterization of the purple dye extracted from the Plicopurpura pansa G. mollusk by HPLC-DAD-MS/MS.
Moreover, this study reveals the simultaneous use of synthetic red dyes with naturally-derived colorants such
as indigo and shellfish purple. The limitations of the various techniques to provide an ultimate identification of
certain dyes are emphasized together with the need for additional foundational research to expand molecular
databases for the identification of synthetic dyes. Nevertheless, the results shed light on a dynamic dyeing
scenario in modern Oaxaca (Mexico), in which traditional materials and methods are used alongside new ones in
an attempt to preserve meaningful local practices.
This paper presents the pigment characterization in six impressionist and post-impressionist pain... more This paper presents the pigment characterization in six impressionist and post-impressionist paintings by three leading Puerto Rican artists: Francisco Oller (1833–1917), José Cuchí y Arnau (1857–1925), and Ramón Frade (1875–1954).
The paintings, belonging to the Corporación de las Artes Musicales and Museo de Arte de Puerto Rico (San Juan, Puerto Rico), were investigated through a combination of complementary non- and micro-invasive scientific techniques.
The use of non-invasive macro-X-ray fluorescence (MA-XRF) and reflectance imaging spectroscopy (RIS) was applied for the first time to characterize Puerto Rican artists’ palette. The non-invasive approach was integrated with spectroscopic techniques such as Raman and/or Fourier-transform infrared (FTIR) spectroscopy, as well as high pressure liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS), when sampling was possible. While this technical investigation reveals pigments that are typical for late 19th/early twentieth century paintings, it also emphasizes some unexpected findings, including the use of cobalt green and synthetic yellow lakes, which enabled the date given to some of the paintings to be refined to post 1910 rather than their current dates of ca. 1890. This study confirms that the Puerto Rican artist’s palettes are very similar to their European
contemporaries, underscoring both their European training and their attempt to adapt these methods of painting to a new Caribbean identity emerging from the Spanish American War.
This study presents the results obtained during the optimization phase of a protocol based on imm... more This study presents the results obtained during the optimization phase of a protocol based on immunofluorescence microscopy (IFM) with the aim to characterize and localize proteins in fluid-rich samples of cultural heritage interest.
Chicken serum albumin from chicken blood was considered the primary target. Ovalbumin from chicken egg albumen (egg white) was also used as a common target protein to test the versatility of the protocol. Mock-ups were created, obtaining a complex distribution of the proteins in a porous matrix, thus providing a good approximation to a real case scenario. Thin sections of 1 µm thickness were then obtained using a cyanoacrylate-based tissue adhesive for the first time in samples of cultural heritage interest. Thin sections were preferred over standard cross sections, as they enabled multiple experiments to be performed by easily generating multiple sections from the same sample. This was particularly important during the optimization phase of the indirect immunochemical procedure, as the concentration of the blocking solutions, primary and secondary antibodies had to be optimized as well as the washing steps, time and temperature of incubation. The use of secondary antibodies conjugated with quantum dots fluorophores and the use of single wavelength structured illumination in the fluorescence microscope set-up reduced the contribution from unspecific fluorescence.
All these technical advances led to the enhanced mapping of the distribution of both ovalbumin and chicken serum albumin in the mock-up samples. The material distribution was also mapped using micro-reflectance imaging spectroscopy, which confirmed the localization of the target materials, thus laying the foundation for a multi-modal imaging protocol, which will be applied to samples taken from fluid-rich patinas on West African sculptures.
Mount components and textile borders represent important elements of Asian paintings. However, th... more Mount components and textile borders represent important elements of Asian paintings. However, they are often side-lined or not considered an integral part of the original piece, as they may be later additions or may have been replaced during historic conservation or mounting interventions. Nevertheless, evidence is sometimes present that textile borders are contemporaneous to the production of the paintings they frame or, in the case of paintings found in archaeological contexts, to the time of deposition. Even when not contemporaneous with the paintings, the mount textiles are often of significant historic interest in themselves, showing a range of complex textile techniques and materials, and highlighting the re-use of fabrics. In all these cases, the study and reconstruction of the original colours of the borders enable further understanding of the holistic visual impact originally intended for the composition, as well as of the role of colour itself, which was used to emphasise, complement or contrast important pictorial themes or motifs in the paintings. Furthermore, the identification of dyes and dyeing techniques has the potential to support the production date and provenance of the paintings. In this study, the textile borders and some additional mounting elements of six paintings (late 9th-10th century CE) from the Library Cave, Mogao Grottoes, Dunhuang, China, one rare Korean portrait painting dated 1789 CE, and two Tibetan thangkas (18th century) were investigated with the aim to identify the dyes present. Fibre optic reflectance spectroscopy (FORS) was used to obtain information non-invasively and, when sampling was possible, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to obtain molecular identification of the dyestuffs employed in their production. Typical Asian dyes, such as gromwell (Lithospermum erythrorhizon), sappanwood (Biancaea sappan), safflower (Carthamus tinctorius), turmeric (Curcuma longa) and pagoda tree flower buds (Sophora japonica), were identified. Some of the dyeing techniques were commensurate with the geographical and temporal provenance assigned to these pieces. Considerations about fading and discolouration of the dyes enabled valuable additional information to be obtained that complements the evidence gleaned from the study of the paintings and informs conservators and curators on best practices in the preservation and display of these precious and delicate artworks.
Commonly exhibited in museum galleries, animal mummies have been the focus of interest of both vi... more Commonly exhibited in museum galleries, animal mummies have been the focus of interest of both visitors and researchers alike. The study of these animal remains not only provides new insights into embalming techniques, but also brings a unique perspective on religious, social and economic practices. Twenty animal mummies are discussed in this study, including cats, ibises, crocodiles, calves and birds of prey from the collections of the British Museum (London, UK) and the Museo Egizio (Turin, Italy). The external textile wrappings encasing the mummified body of the animals were investigated with the main aim of identifying the colourants used. In fact, these are mostly patterned using undyed and coloured (mostly red, brown and black) linen strips. Broadband multispectral imaging (MSI) was initially carried out to obtain preliminary information at the macro-scale on the distribution and chemical nature of the colouring agents. Fibre optic reflectance spectroscopy (FORS) was then used to survey several coloured areas of the textile wrappings. Safflower (Carthamus tinctorius) and red ochre were identified non-invasively. Representative samples were then taken and observed using optical microscopy (OM) and scanning electron microscopy (SEM), in order to obtain information at the micro-scale on the distribution of the colouring agents on the fibres, as well as the presence of other materials, including those from environmental contamination. Energy dispersive X-ray spectrometry (EDX) revealed the elemental composition of particles and clear areas of the fibres, whereas high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) provided the identification of the organic dyes at a molecular level. The use of hydrolysable and condensed tannins, in combination with iron as a mordant, was found to be used in the very dark shades, which generally corresponded to the textiles with the worst state of preservation. Nevertheless, other aspects, such as fibre processing and bleaching, fungal attack and presence of coating materials appeared to play a role in the evaluation of the conservation state of these textiles. The characterisation of the dyes and the additional inorganic materials contributed to elucidating the production technology of the colours used for animal mummification, and provided insights into ancient dyeing methods.
In the past 30 years the study of the composition and chemistry of Asian lacquers has reached a h... more In the past 30 years the study of the composition and chemistry of Asian lacquers has reached a high level of interest among scientists and conservators. As a result, analytical strategies have been developed to characterise and identify these materials in complex samples, sometimes thousands of years old.
Asian lacquers are mainly composed of polymerised alkylcatechols and they are often applied in mixtures with several other organic and inorganic materials, such as oils, plant gums, mineral pigments, organic additives, etc. The polymeric nature of Asian lacquers limits the scientific approaches that can be used to investigate them. Technological progress and an increase in popularity of analytical pyrolysis (Py) have run parallel to the advancement of research in the field of Asian lacquer identification. With the ability to distinguish the different types of lacquers and to identify most of the other materials mixed with them, pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) is the most effective technique in this type of investigation. Several research groups have optimised analytical conditions, derivatisation steps and data treatment to create reliable protocols with wide applicability.
The information related to the development of such protocols is summarised in this review, together with some critical comparisons and suggestions on future perspectives in this research field.
This study focuses on the analysis of 61 samples taken from wool fabric specimens present in the ... more This study focuses on the analysis of 61 samples taken from wool fabric specimens present in the appendix of the book “A Manual of Dyeing: For the Use of Practical Dyers, Manufacturers, Students, and All Interested in the Art of Dyeing” by E. Knecht, C. Rawson and R. Loewenthal, published in England in 1893. This manual is a valuable source of information, as it partially describes the chemistry of the molecules used to dye the specimens. The dyes are presented with the common commercial names used at the end of the 19th century and the publication date ensures that they were all synthesized before 1893.
The first aim of the study was to explore the correspondence between the dyes described in the manual and the molecules actually present in the samples. High performance liquid chromatography coupled to diode array and mass spectrometric detectors (HPLC-DAD-MS) was used for the molecular characterization of the samples. The results were integrated with a thorough search of historic information on early synthetic dyes, to clarify the dye nomenclature, and ultimately the molecular structures of the detected molecules.
The results showed that the labels reported in the manual often do not correspond to the actual dyes present in the samples. In a number of cases, mixtures of dyes of different categories were actually used to obtain a certain color shade. We created a database of more than 160 molecules, including their UV–Vis absorption spectra and MS details, many of which are not reported in the scientific literature. This represents a valuable new comparative dataset useful for the identification of these molecules in historic samples.
Book: Analytical Strategies for Cultural Heritage Materials and their Degradation, 2021
Ceramics, stones, metallic objects, bones, leather, wood and textiles are among the most importan... more Ceramics, stones, metallic objects, bones, leather, wood and textiles are among the most important categories of archaeological remains. The information carried by these materials is often invaluable, as they represent precious and sometimes unique windows into past civilizations and into the evolution of humankind. Scientific research has the aim of selecting the most suitable analytical techniques in order to characterize these materials and retrieve the maximum amount of information possible without compromising the integrity of the objects. In a parallel way, conservation strategies have been extensively researched with the intention of preserving this precious archaeological evidence for future generations. However, both scientific and conservation research must first take into account the characteristics of the burial environments and their impact on the state of preservation of archaeological remains. This is particularly important for organic materials, as these are naturally degraded in most common conditions and are therefore relatively rare in archaeological findings. This chapter discusses the burial environments that permit the survival of archaeological materials, and also the implications that specific environmental agents have on the state of preservation of such materials. The analytical approaches used to scientifically investigate archaeological objects, assess their state of preservation and support conservation choices are also presented.
This review describes the capability of analytical pyrolysis-based techniques to provide
data on ... more This review describes the capability of analytical pyrolysis-based techniques to provide data on lignin composition and on the chemical alteration undergone by lignin in archaeological wooden objects. Applications of Direct Exposure Mass Spectrometry (DE-MS), Evolved Gas Analysis Mass Spectrometry (EGA-MS), and single and double-shot Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) in archaeological lignin characterisation are described. With comparison to cellulose and hemicelluloses, lignin is generally less prone to most degradation processes affecting archaeological artefacts in burial environments, especially waterlogged ones, which are the most favourable for wood preservation. Nevertheless, lignin also undergoes significant chemical changes. As wood from waterlogged environments is mainly composed of lignin, knowledge of its chemical structure and degradation pathways is fundamental for choosing preventive conservation conditions and for optimising consolidation methods and materials, which directly interact with the residual lignin. Analytical pyrolysis coupled with mass spectrometry, used in several complementary operational modes, can gather information regarding the chemical modifications and the state of preservation of lignin, especially concerning oxidation and depolymerisation phenomena. Several applications to the analysis of wood from archaeological artefacts affected by different conservation problems are presented to showcase the potential of analytical pyrolysis in various scenarios that can be encountered when investigating archaeological waterlogged wood.
Three Japanese woodblock prints from the Edo period (1603-1868) underwent a scientific investigat... more Three Japanese woodblock prints from the Edo period (1603-1868) underwent a scientific investigation with the aim of understanding the changes in the colorants used in Japanese printing techniques. A multi-analytical approach was adopted, combining non-invasive techniques, such as fiber optic reflectance spectroscopy (FORS), Raman spectroscopy, multispectral imaging (MSI), and macro X-ray fluorescence (MA-XRF) with minimally invasive surface-enhanced Raman spectroscopy (SERS). The results enabled many of the pigments to be identified and their distribution to be studied, apart from two shades of purple of organic composition. Consequently, the potential of high-pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was explored for the first time with application to Japanese woodblock prints. The intrinsic sensitivity of the instrument and an effective extraction protocol allowed us to identify a mixture of dayflower (Commelina communis) blue and safflower (Carthamus tinctorius) red in purple samples constituted of 2-3 single fibers. In addition to the innovative integration of MA-XRF and HPLC-MS/MS to investigate these delicate artworks, the study concluded on the use of traditional sources of colors alongside newly introduced pigments in late Edo-period Japan. This information is extremely important for understanding the printing practices, as well as for making decisions about display, conservation, and preservation of such artworks. Japanese woodblock prints are among the most popular forms of artworks on paper. The prints usually depict ordinary elements of life, such as landscapes, tales from history, scenes from the Kabuki theatre, as well as courtesans, or geishas. Due to their low manufacture cost, woodblock prints were mass produced and widely distributed. In the Edo period (1603-1868 AD), Japanese prints became one of the dominant art movements. The vibrant colors and extremely various palette of nuances, as well as the particularly appealing style of this form of art, have not only attracted the eyes of collectors for centuries, but also continue to capture the attention of the general museum public. Nowadays, Japanese woodblock prints can be found in great numbers in many museum collections, including the Metropolitan Museum of Art's (New York City, USA).
A successful application of Er:YAG laser for the cleaning of a restored Assyrian relief sculpture... more A successful application of Er:YAG laser for the cleaning of a restored Assyrian relief sculpture from the British Museum collection is presented. Displayed in the gallery, the sculpture has darkened over time due to the natural deposition of dirt, in particular on restored parts. Since traditional cleaning methods have demonstrated to be unsuccessful, a scientific investigation was performed to identify the composition of the soiling and the materials used for the restoration. The analysis suggested the presence of gypsum, calcium oxalate, carbonates and alumino-silicates on the encrustation. The molded plaster, composed of lime and gypsum and pigmented aggregates, was likely prepared at the end of the 19th century to mimic the stone color. It was repainted with what was identified as a modern oil-based overpaint, applied to cover darkening during a second conservation treatment in the 20th century. Laser trials were first performed on small areas of the objects and on mock-ups to determine the critical fluence thresholds of the surface, investigated through visual examination and analyses using Fourier transform infrared spectroscopy (FTIR) and Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The right parameters and conditions to be used during the cleaning process were, therefore, determined. The chemical selectivity of the cleaning process allowed us to complete the treatment safely while preserving the restoration.
This study focuses on the dye analysis of 26 ikat textiles present in the collection of the Arthu... more This study focuses on the dye analysis of 26 ikat textiles present in the collection of the Arthur M. Sackler Gallery and originally collected by Dr. Guido Goldman with the aim to gain additional information about their provenance and dating. The investigation exploits the full potential of a multi-analytical approach, starting with a non-invasive survey of all the colors using fiber optic reflectance spectroscopy (FORS), which revealed the presence of indigo and insect-based red dyes. These data were used to select areas from which samples were taken and analyzed by high performance liquid chromatography diode array detector (HPLC-DAD). These results enabled most of the natural sources of dyes to be fully identified, including American cochineal (Dactylopius coccus), madder (probably Rubia tinctorum), lac (probably Kerria lacca), larkspur (Delphinum semibarbatum), pagoda tree flower buds (Sophora japonica), grape vine leaves (Vitis vinifera), indigo and tannins. Complex mixtures of dyes were present in most samples, as a result of both the ikat making process itself and traditional dyeing practices. Synthetic dyes were identified in 9 of the textiles. Samples were re-analyzed using HPLC-DAD coupled to mass spectrometry (HPLC-DAD-MS). Malachite green (basic green 4, C.I. 42000), fuchsine (basic violet 14, C.I. 42510), rhodamine B (basic violet 10, C.I. 45170) and methyl violet (basic violet 1, C.I. 42535) were identified, and a few other tentatively identified synthetic dyes (probably orange I, II and IV, rhodamine 6G, patent blue V and alizarin yellow GG) were detected. As the first synthesis of early synthetic dyes is well documented, their presence was used to refine the dating of these textiles. The contextualization of the results also appeared to support the stylistic assumption that more intricate and colorful designs with a higher level of complexity are dated earlier than simpler, larger and more graphic ones. The overall information acquired reveals a dynamic scenario and an interesting window into the dyers' experiments and adjustments to the economic and technological changes of the nineteenth century.
People in north-east Brazil mostly rely on fuelwood and charcoal for domestic energy consumption.... more People in north-east Brazil mostly rely on fuelwood and charcoal for domestic energy consumption. Traditionally, four local wood taxa (Mimosa tenuiflora, Mimosa ophthalmocentra, Croton sonderianus and Cenostigma pyramidale) from the caatinga have been selected for this purpose. As the final quality of charcoal is directly related to the charring conditions, as well as the chemical composition of the raw materials and the behaviour of the lignocellulosic matrix during the charring process, the aim of this study was to investigate how far differences in these parameters exert a major control on the charcoal formation, in order to give a molecular insight as to why these particular wood species might be preferred for high-quality charcoal in the perspective of sustainable management and harvesting regimes. Pyrolysis gas chromatography mass spectrometry (Py-GC-MS) and scanning electron microscopy (SEM) were used to study the chemical composition and anatomical changes of the wood samples before and after charring experiments were carried out at 400 and 600 °C. The charring conditions were also reproduced in the controlled environment of the pyrolysis chamber and evolved gas analysis mass spectrometry (EGA-MS) was used for the first time to monitor the evolution of the thermal degradation products. The thermal behaviour of the wood components was different compared to other wood taxa for which comparable data are available. These differences were partially related to the particular nature of the carbohydrate-lignin interactions, to a relatively low level of lignin condensation, and to the substantial presence of gums or resins, which formed charred deposits. These characteristics, often neglected in charcoal analysis, imply that the wood components (especially cellulose) are released more slowly during the charring process, and this translates into the ability of these wood species to retain the main features of their anatomical structure even when exposed to high temperature for a relatively long time. The anatomical alterations observed, such as the loss of the middle lamella, the disappearance of the pit membranes, and the homogenisation of cell walls are ultimately in agreement with the formation of a particularly recalcitrant carbonaceous matrix upon charring at relatively low temperature (400 °C for 2 hours). This study presents the first molecular characterisation of these wood species and some methodological advancement on the use of EGA analysis using isothermal conditions is provided. The role of carbohydrate-lignin interactions and non-lignocellulosic wood components in charcoal production is discussed and the importance of combining chemical data and anatomical observations in wood research is underlined.
Identification of Asian lacquers in museum objects is a challenging task. Their identification by... more Identification of Asian lacquers in museum objects is a challenging task. Their identification by mass spectrometry is based on molecular marker recognition, and analysis of chromatographic profiles of several types of molecules. A summary of published markers and chromatographic profiles ‒ obtained with and without thermally assisted reactions (silylation and methylation) ‒ is included in this paper. Based on this, a decision-making scheme was established, and proposed to guide data interpretation. This method of data analysis was then applied to a group of lacquered objects belonging to the Asian art collection of the Museum of Zaragoza (Spain). Based on stylistic and art historical information, the objects are dated from the 16th to the 20th century and attributed to Japanese, Chinese, Burmese and Thai manufacture. Analytical pyrolysis with in situ silylation - gas chromatography coupled with mass spectrometry (Py(HMDS)-GC/MS) was used to analyse the lacquers, and scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS) was used on cross sections to study the stratigraphy of the objects and understand the artistic techniques. The proposed scheme proved to be a useful analytical guide for the straightforward identification of the lacquer origin, even when this is present in mixture with other organic materials. In fact, a multi-faceted picture emerged, as some of the objects showed interesting mixtures of lacquers, such as urushi and thitsi, or unexpected compositions, which questioned their initial attributions. Complex or unexpectedly simple preparations and restoration treatments of the decorative surfaces were highlighted as well, supporting the museological investigation of these objects, in order to confirm/reject their authenticity and geographical provenance.
Study day held at the British Museum Asia study room on 1 April 2019. A day of presentations focu... more Study day held at the British Museum Asia study room on 1 April 2019. A day of presentations focusing on objects brought back by Sir Aurel Stein from the Silk Roads, many of which were officially accessioned at the Museum in 1919, one hundred years ago.
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Papers by Diego Tamburini
weddings, etc. They have been traditionally dyed with three natural dyes, namely indigo, cochineal, and
shellfish purple. In this study two modern enredos produced in the 1980s, now in the collection of the National
Museum of Mexican Art, were investigated with the aim of understanding the colorants used and informing on
the use of traditional dyeing practices in modern Oaxaca.
The results were obtained by a combination of non-invasive analytical techniques, namely reflectance imaging
spectroscopy (RIS) and macro X-ray fluorescence (MA-XRF), and high pressure liquid chromatography coupled to
diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). In addition to representing the first
example of this combination of techniques applied to the study of textiles, this study also reports on the first
characterization of the purple dye extracted from the Plicopurpura pansa G. mollusk by HPLC-DAD-MS/MS.
Moreover, this study reveals the simultaneous use of synthetic red dyes with naturally-derived colorants such
as indigo and shellfish purple. The limitations of the various techniques to provide an ultimate identification of
certain dyes are emphasized together with the need for additional foundational research to expand molecular
databases for the identification of synthetic dyes. Nevertheless, the results shed light on a dynamic dyeing
scenario in modern Oaxaca (Mexico), in which traditional materials and methods are used alongside new ones in
an attempt to preserve meaningful local practices.
The paintings, belonging to the Corporación de las Artes Musicales and Museo de Arte de Puerto Rico (San Juan, Puerto Rico), were investigated through a combination of complementary non- and micro-invasive scientific techniques.
The use of non-invasive macro-X-ray fluorescence (MA-XRF) and reflectance imaging spectroscopy (RIS) was applied for the first time to characterize Puerto Rican artists’ palette. The non-invasive approach was integrated with spectroscopic techniques such as Raman and/or Fourier-transform infrared (FTIR) spectroscopy, as well as high pressure liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS), when sampling was possible. While this technical investigation reveals pigments that are typical for late 19th/early twentieth century paintings, it also emphasizes some unexpected findings, including the use of cobalt green and synthetic yellow lakes, which enabled the date given to some of the paintings to be refined to post 1910 rather than their current dates of ca. 1890. This study confirms that the Puerto Rican artist’s palettes are very similar to their European
contemporaries, underscoring both their European training and their attempt to adapt these methods of painting to a new Caribbean identity emerging from the Spanish American War.
Chicken serum albumin from chicken blood was considered the primary target. Ovalbumin from chicken egg albumen (egg white) was also used as a common target protein to test the versatility of the protocol. Mock-ups were created, obtaining a complex distribution of the proteins in a porous matrix, thus providing a good approximation to a real case scenario. Thin sections of 1 µm thickness were then obtained using a cyanoacrylate-based tissue adhesive for the first time in samples of cultural heritage interest. Thin sections were preferred over standard cross sections, as they enabled multiple experiments to be performed by easily generating multiple sections from the same sample. This was particularly important during the optimization phase of the indirect immunochemical procedure, as the concentration of the blocking solutions, primary and secondary antibodies had to be optimized as well as the washing steps, time and temperature of incubation. The use of secondary antibodies conjugated with quantum dots fluorophores and the use of single wavelength structured illumination in the fluorescence microscope set-up reduced the contribution from unspecific fluorescence.
All these technical advances led to the enhanced mapping of the distribution of both ovalbumin and chicken serum albumin in the mock-up samples. The material distribution was also mapped using micro-reflectance imaging spectroscopy, which confirmed the localization of the target materials, thus laying the foundation for a multi-modal imaging protocol, which will be applied to samples taken from fluid-rich patinas on West African sculptures.
Asian lacquers are mainly composed of polymerised alkylcatechols and they are often applied in mixtures with several other organic and inorganic materials, such as oils, plant gums, mineral pigments, organic additives, etc. The polymeric nature of Asian lacquers limits the scientific approaches that can be used to investigate them. Technological progress and an increase in popularity of analytical pyrolysis (Py) have run parallel to the advancement of research in the field of Asian lacquer identification. With the ability to distinguish the different types of lacquers and to identify most of the other materials mixed with them, pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) is the most effective technique in this type of investigation. Several research groups have optimised analytical conditions, derivatisation steps and data treatment to create reliable protocols with wide applicability.
The information related to the development of such protocols is summarised in this review, together with some critical comparisons and suggestions on future perspectives in this research field.
The first aim of the study was to explore the correspondence between the dyes described in the manual and the molecules actually present in the samples. High performance liquid chromatography coupled to diode array and mass spectrometric detectors (HPLC-DAD-MS) was used for the molecular characterization of the samples. The results were integrated with a thorough search of historic information on early synthetic dyes, to clarify the dye nomenclature, and ultimately the molecular structures of the detected molecules.
The results showed that the labels reported in the manual often do not correspond to the actual dyes present in the samples. In a number of cases, mixtures of dyes of different categories were actually used to obtain a certain color shade. We created a database of more than 160 molecules, including their UV–Vis absorption spectra and MS details, many of which are not reported in the scientific literature. This represents a valuable new comparative dataset useful for the identification of these molecules in historic samples.
data on lignin composition and on the chemical alteration undergone by lignin in archaeological
wooden objects. Applications of Direct Exposure Mass Spectrometry (DE-MS), Evolved Gas Analysis
Mass Spectrometry (EGA-MS), and single and double-shot Pyrolysis-Gas Chromatography/Mass
Spectrometry (Py-GC/MS) in archaeological lignin characterisation are described. With comparison
to cellulose and hemicelluloses, lignin is generally less prone to most degradation processes
affecting archaeological artefacts in burial environments, especially waterlogged ones, which are the
most favourable for wood preservation. Nevertheless, lignin also undergoes significant chemical
changes. As wood from waterlogged environments is mainly composed of lignin, knowledge of its
chemical structure and degradation pathways is fundamental for choosing preventive conservation
conditions and for optimising consolidation methods and materials, which directly interact with the
residual lignin. Analytical pyrolysis coupled with mass spectrometry, used in several complementary
operational modes, can gather information regarding the chemical modifications and the state of
preservation of lignin, especially concerning oxidation and depolymerisation phenomena. Several
applications to the analysis of wood from archaeological artefacts affected by different conservation
problems are presented to showcase the potential of analytical pyrolysis in various scenarios that can
be encountered when investigating archaeological waterlogged wood.
weddings, etc. They have been traditionally dyed with three natural dyes, namely indigo, cochineal, and
shellfish purple. In this study two modern enredos produced in the 1980s, now in the collection of the National
Museum of Mexican Art, were investigated with the aim of understanding the colorants used and informing on
the use of traditional dyeing practices in modern Oaxaca.
The results were obtained by a combination of non-invasive analytical techniques, namely reflectance imaging
spectroscopy (RIS) and macro X-ray fluorescence (MA-XRF), and high pressure liquid chromatography coupled to
diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). In addition to representing the first
example of this combination of techniques applied to the study of textiles, this study also reports on the first
characterization of the purple dye extracted from the Plicopurpura pansa G. mollusk by HPLC-DAD-MS/MS.
Moreover, this study reveals the simultaneous use of synthetic red dyes with naturally-derived colorants such
as indigo and shellfish purple. The limitations of the various techniques to provide an ultimate identification of
certain dyes are emphasized together with the need for additional foundational research to expand molecular
databases for the identification of synthetic dyes. Nevertheless, the results shed light on a dynamic dyeing
scenario in modern Oaxaca (Mexico), in which traditional materials and methods are used alongside new ones in
an attempt to preserve meaningful local practices.
The paintings, belonging to the Corporación de las Artes Musicales and Museo de Arte de Puerto Rico (San Juan, Puerto Rico), were investigated through a combination of complementary non- and micro-invasive scientific techniques.
The use of non-invasive macro-X-ray fluorescence (MA-XRF) and reflectance imaging spectroscopy (RIS) was applied for the first time to characterize Puerto Rican artists’ palette. The non-invasive approach was integrated with spectroscopic techniques such as Raman and/or Fourier-transform infrared (FTIR) spectroscopy, as well as high pressure liquid chromatography coupled to diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS), when sampling was possible. While this technical investigation reveals pigments that are typical for late 19th/early twentieth century paintings, it also emphasizes some unexpected findings, including the use of cobalt green and synthetic yellow lakes, which enabled the date given to some of the paintings to be refined to post 1910 rather than their current dates of ca. 1890. This study confirms that the Puerto Rican artist’s palettes are very similar to their European
contemporaries, underscoring both their European training and their attempt to adapt these methods of painting to a new Caribbean identity emerging from the Spanish American War.
Chicken serum albumin from chicken blood was considered the primary target. Ovalbumin from chicken egg albumen (egg white) was also used as a common target protein to test the versatility of the protocol. Mock-ups were created, obtaining a complex distribution of the proteins in a porous matrix, thus providing a good approximation to a real case scenario. Thin sections of 1 µm thickness were then obtained using a cyanoacrylate-based tissue adhesive for the first time in samples of cultural heritage interest. Thin sections were preferred over standard cross sections, as they enabled multiple experiments to be performed by easily generating multiple sections from the same sample. This was particularly important during the optimization phase of the indirect immunochemical procedure, as the concentration of the blocking solutions, primary and secondary antibodies had to be optimized as well as the washing steps, time and temperature of incubation. The use of secondary antibodies conjugated with quantum dots fluorophores and the use of single wavelength structured illumination in the fluorescence microscope set-up reduced the contribution from unspecific fluorescence.
All these technical advances led to the enhanced mapping of the distribution of both ovalbumin and chicken serum albumin in the mock-up samples. The material distribution was also mapped using micro-reflectance imaging spectroscopy, which confirmed the localization of the target materials, thus laying the foundation for a multi-modal imaging protocol, which will be applied to samples taken from fluid-rich patinas on West African sculptures.
Asian lacquers are mainly composed of polymerised alkylcatechols and they are often applied in mixtures with several other organic and inorganic materials, such as oils, plant gums, mineral pigments, organic additives, etc. The polymeric nature of Asian lacquers limits the scientific approaches that can be used to investigate them. Technological progress and an increase in popularity of analytical pyrolysis (Py) have run parallel to the advancement of research in the field of Asian lacquer identification. With the ability to distinguish the different types of lacquers and to identify most of the other materials mixed with them, pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS) is the most effective technique in this type of investigation. Several research groups have optimised analytical conditions, derivatisation steps and data treatment to create reliable protocols with wide applicability.
The information related to the development of such protocols is summarised in this review, together with some critical comparisons and suggestions on future perspectives in this research field.
The first aim of the study was to explore the correspondence between the dyes described in the manual and the molecules actually present in the samples. High performance liquid chromatography coupled to diode array and mass spectrometric detectors (HPLC-DAD-MS) was used for the molecular characterization of the samples. The results were integrated with a thorough search of historic information on early synthetic dyes, to clarify the dye nomenclature, and ultimately the molecular structures of the detected molecules.
The results showed that the labels reported in the manual often do not correspond to the actual dyes present in the samples. In a number of cases, mixtures of dyes of different categories were actually used to obtain a certain color shade. We created a database of more than 160 molecules, including their UV–Vis absorption spectra and MS details, many of which are not reported in the scientific literature. This represents a valuable new comparative dataset useful for the identification of these molecules in historic samples.
data on lignin composition and on the chemical alteration undergone by lignin in archaeological
wooden objects. Applications of Direct Exposure Mass Spectrometry (DE-MS), Evolved Gas Analysis
Mass Spectrometry (EGA-MS), and single and double-shot Pyrolysis-Gas Chromatography/Mass
Spectrometry (Py-GC/MS) in archaeological lignin characterisation are described. With comparison
to cellulose and hemicelluloses, lignin is generally less prone to most degradation processes
affecting archaeological artefacts in burial environments, especially waterlogged ones, which are the
most favourable for wood preservation. Nevertheless, lignin also undergoes significant chemical
changes. As wood from waterlogged environments is mainly composed of lignin, knowledge of its
chemical structure and degradation pathways is fundamental for choosing preventive conservation
conditions and for optimising consolidation methods and materials, which directly interact with the
residual lignin. Analytical pyrolysis coupled with mass spectrometry, used in several complementary
operational modes, can gather information regarding the chemical modifications and the state of
preservation of lignin, especially concerning oxidation and depolymerisation phenomena. Several
applications to the analysis of wood from archaeological artefacts affected by different conservation
problems are presented to showcase the potential of analytical pyrolysis in various scenarios that can
be encountered when investigating archaeological waterlogged wood.