In-Between Textiles, 1400–1800 Weaving Subjectivities and Encounters, 2023
This chapter presents the results of a decade-long study on the appropriation of American cochine... more This chapter presents the results of a decade-long study on the appropriation of American cochineal in early modern European textile industries. The comparative study is based on in-depth archival research and a new scientific approach that allows, for the first time, the accurate distinction of insect dyes in historical textiles. Revealing the gradual adoption of New World dyestuff, the chapter shifts established narratives and calls for attention to the very material composition of in-between textiles. Actual matter inhabited these fabrics’ Third Space, whose material composition changed in response to early modern colonialism and consumerism.
Textiles, Trade & Taste: Portugal and the World (TTT) is a project that aspires to bring new syne... more Textiles, Trade & Taste: Portugal and the World (TTT) is a project that aspires to bring new synergies to the field of textile studies by promoting different connections and interdisciplinary approaches involving art history, materials science, and conservation. The TTT research network is based at the Center for Humanities in the School of Social Sciences and Humanities at the Universidade NOVA de Lisboa and organizes workshops, conferences, tours, and lectures in museums and research institutions. The network’s artistic and historical research has ranged from collating archival material to stylistic and iconographic studies, with the aim of placing textile objects in their historical, artistic, technological, and sociocultural contexts. Chemical analysis and characterization of dyes, textile fibers, and precious metal threads have provided important evidence for identifying the origins of raw materials and finished textiles, and for developing improved conservation treatments for their preservation for future generations. Recent research has examined the global circulation of dyes in the early modern period, especially reds, and also reconstructed the production and consumption of Indian, Chinese, and Portuguese embroideries and Islamic carpets. In 2011, TTT’s work led to the classification of three “Salting” carpets as national treasures in Portugal. The team members have collaborated with national and international museums, including Museu Nacional de Arte Antiga and Calouste Gulbenkian Museum (Lisbon), as well as Abegg-Stiftung (Riggisberg), The Metropolitan Museum of Art (New York), Musée des Tissus, (Lyon), Museum für Islamische Kunst (Berlin), Museum für angewandte Kunst (MAK) (Vienna), Rietberg Museum (Zürich), Rijksmuseum (Amsterdam), George Washington University Museum and The Textile Museum (Washington, D.C.), National Gallery of Art (Washington, D.C.), and Victoria and Albert Museum (London). The team’s art historians contributed to the platform “Museum With No Frontiers” to develop the online exhibition Discover Carpet Art involving Portuguese museums. TTT’s scientists have strong links with the Freer Gallery of Art and Arthur M. Sackler Gallery (National Museum of Asian Art, Washington, D.C.), University of Zaragoza (Spain), Rijksdienst voor het Cultureel Erfgoed (Cultural Heritage Agency of the Netherlands, Amersfoort), and the University of Amsterdam. We have been encouraged by the positive response of the international community to the results of our initial research projects.
tThe appraisal of the design and the weaving structure of Islamic knotted-pile carpets can tell p... more tThe appraisal of the design and the weaving structure of Islamic knotted-pile carpets can tell plentyabout the context in which they were produced, and the identification of signs of deterioration can helpto establish their condition. These are often somewhat imprecise and laborious examinations, especiallywhen considering carpets of large dimensions. Analytical methods that support these disciplines urgefurther exploration so that improved interpretations can be obtained.An interdisciplinary combination of art history, analytical science and textile conservation aimed, onthe one hand, to improve the weaving examination of these complex textile objects – by considering thespin of threads and the ply of yarns; the knot count and density; and the weaving structure of warps, weftsand piles – and on the other, to help their condition assessment – by mapping of damaged areas, old repairsand contaminations. For this purpose, the possibilities and limitations of several non-invasive imagingtechniques, namely transmitted, raking or incident visible, ultraviolet (UV) and infrared (IR) illuminationthrough Visual Spectral Comparator (VSC), as well as conventional X-radiography, mammography and(micro) CT scanning, were assessed to support the conventional visual examination of the weaving detailsand present condition of two 17th-century Safavid knotted-pile carpet fragments.Observation with NUV and NIR imaging with VSC, as well as CT techniques, offered enriching over-views about weaving characteristics, damaged areas or contaminations that were not easily discerniblewith the naked eye, thus supporting the conventional visual examination. As a result, detailed digitalmappings about the technological structure and the condition of the fragments could be obtained in arelatively efficient and accessible way. Moreover, combining art historical identification of the designwith the analysis of the weaving structure confirmed that both carpet fragments are border corners thatoriginally belonged to much larger carpets made in the so-called “Indo-Persian” style. The outcome ofthis interdisciplinary research brings very useful contributions for future art historical and conservationassessments of historical carpets, and it encourages further exploration of imaging techniques in theexamination of other textile objects in museums and private collections.
An exceptional group of silk fragments was unearthed in 2014 from a shipwreck, which sank in the ... more An exceptional group of silk fragments was unearthed in 2014 from a shipwreck, which sank in the mid-17th century, in the Wadden Sea, The Netherlands. A unique example of 17th-century fashion, it comprises about 300 textile fragments from garments, parts of garments and furnishing fabrics, almost entirely made of silk and embroidered or woven with metal thread. These are in remarkably good condition, which may be related to the archaeological environment, the quality of the silk yarns in the fragments, and the presence of metal threads and other metallic objects from the shipwreck. Surviving archaeological maritime silk textiles are extremely rare, which makes this a distinctive find posing challenges for selecting the most suitable conditions for exhibition and storage.
Scientific research was carried out with the aim to evaluate the response of modern and archaeological silks to temperature, relative humidity, light and oxygen, in order to define the most suitable parameters for the long-term storage and exhibition of the collection. Artificially aged samples taken from one of the archaeological fragments were analysed at the visual, structural and molecular level by means of colour measurements, Fourier transform infrared spectroscopy (FTIR) and ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FLD). The results showed that light exposure, in combination with high temperatures, oxygen and moisture strongly affected the silk's structure and molecular composition. Limiting exposure to light and removing oxygen reduced this effect and increased life expectancy significantly. Therefore, the analytical results obtained were essential to defining a preliminary preservation strategy for the collection: while on display, anoxic conditions slow down degradation of the silk by a factor of 4–5, whereas in a in dark storage, a low RH is the most important factor, with anoxic conditions providing additional reduction of decay.
Proceedings of the Natuurlijk Kleuren Symposium Nov. 2017, Textielcommissie, 2020
From the beginning of the 16th century, the Portuguese and the Spanish brought growing quantities... more From the beginning of the 16th century, the Portuguese and the Spanish brought growing quantities of dyes from the Americas to Europe, namely cochineal, indigo, brazilwood and logwood. All these enjoyed increasing positions in transatlantic shipments, particularly cochineal, which ranked in price after silver and gold in Spanish cargoes. Later in the century, the Dutch, English and French also entered the transatlantic trade and, subsequently, American dyes no longer passed exclusively through the Iberian Peninsula.
Once in Europe, American dyes had a decisive impact on long-established dyeing traditions. Not only they allowed a wider range of colours, but they were also economically advantageous over European dyes. For instance, cochineal and indigo presented higher contents of colorant in relation to related local dyes, which allowed for larger numbers of cloth to be coloured. Hence, they were soon assimilated in the main European centres of textile production. However, in some regions, textile producers continued to prefer local dyes over the new ones.
An interdisciplinary investigation explored the diverse response of European territories to the trade and assimilation of American dyes in the textile centres, during the 16th and the 17th centuries. By combining historical research and chemical analyses of colorants in historical textiles, it was revealed that this process seems to have happened gradually, with more or less resistance, depending on the political and economic circumstances of each territory.
In de zomer van 2014 is een grote collectie 17de-eeuws textiel gevonden in een scheepswrak bij Te... more In de zomer van 2014 is een grote collectie 17de-eeuws textiel gevonden in een scheepswrak bij Texel. De collectie is overgedragen aan Museum Kaap Skil te Texel en is later naar de rechtmatige eigenaar, de Provincie Noord-Holland, gegaan. In het najaar van 2015 is contact gezocht met de Universiteit van Amsterdam, conservering en restauratie van cultureel erfgoed (UvA-C&R) om mee te helpen met het beheer en behoud van het textiel.
The colorant behaviour of cochineal and kermes insect dyes in 141 experimentally-dyed and 28 arti... more The colorant behaviour of cochineal and kermes insect dyes in 141 experimentally-dyed and 28 artificially-aged samples of silk and wool was investigated using ultra-high performance liquid chromatography coupled to photodiode array detector (UHPLC-PDA), liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS) and image scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDX). Partial-least squares discriminant analysis (PLS-DA) was then used to model the acquired UHPLC-PDA data and assess the possibility of discriminating cochineal insect species, as well as their correspondent dyed and aged reference fibres. The resulting models helped to characterize a set of 117 red samples from 95 historical textiles, in which UHPLC-PDA analyses have reported the presence of cochineal and kermes insect dyes.
Analytical investigation of the experimentally-dyed and artificially-aged fibres has demonstrated that the ratio of compounds in the insects dye composition can change, depending on the dyeing conditions applied and the type of fibres used. Similarities were observed when comparing the UHPLC-MS and SEM-EDX results from the dyed and aged references with the historical samples. This was verified with PLS-DA models of the chromatographic data, facilitating the classification of the cochineal species present in the historical samples. The majority of these samples were identified to contain American cochineal, which is in agreement with historical and dye identification literature that describe the impact of this dyestuff into European and Asian dyeing practices, after the Iberian Expansion in the 16th century.
The analytical results emphasize the importance of using statistical data interpretation for the discrimination of cochineal dyes, besides qualitative and quantitative evaluation of chromatograms. Hence, the combination of UHPLC-PDA with a statistical classification method, such as PLS-DA, has been demonstrated to be an advisable approach in future investigations to assess closely related species of natural dyes in historical textile samples. This is particularly important when aiming to achieve more accurate interpretations about the history of works of art, or the application of natural dyes in old textile production.
Catharijne - Magazine van Museum Catharijneconvent: Het geheim van de Middeleeuwen in gouddraad en zijde
In het kader van het project The Red Road of the Iberian Expansion: Cochineal and the Global Dye ... more In het kader van het project The Red Road of the Iberian Expansion: Cochineal and the Global Dye Trade zijn de oorspronkelijke kleuren van historisch textiel uit de collectie van Museum Catharijneconvent bestudeerd. Het doel hiervan was om het gebruik van lokale en geïmporteerde kleurstoffen, in de Europese verfindustrie in de overgangsperiode van de late Middeleeuwen naar de nieuwe tijd, te achterhalen, met name de kleurstof afkomstig van de Cochenille luis.
In the framework of the project “THE RED ROAD OF THE IBERIAN EXPANSION: Cochineal and the Global Dye Trade”, the colours of historical textiles belonging to the Catharijnconvent museum collection were studied to assess the use of local and faraway- imported sources of colour, especially cochineal, into the European dyeing industry, in the transition between the Middle Ages and the beginning of the Age of Discoveries.
An evaluation was undertaken of ultrahigh pressure liquid chromatography (UHPLC) in comparison to... more An evaluation was undertaken of ultrahigh pressure liquid chromatography (UHPLC) in comparison to high-performance liquid chromatography (HPLC) for characterizing natural dyes in cultural heritage objects. A new UHPLC method was optimized by testing several analytical parameters adapted from prior UHPLC studies developed in diverse fields of research. Different gradient elution programs were tested on seven UHPLC columns with different dimensions and stationary phase compositions by applying several mobile phases, flow rates, temperatures, and runtimes. The UHPLC method successfully provided more improved data than that achieved by the HPLC method. Indeed, even though carminic acid has shown circa 146% higher resolution with HPLC, UHPLC resulted in an increase of 41 to 61% resolution and a decrease of 91 to 422% limit of detection, depending on the dye compound. The optimized method was subsequently assigned to analyse 59 natural reference materials, in which 85 different components were ascribed with different physicochemical properties, in order to create a spectral database for future characterization of dyes in cultural heritage objects. The majority of these reference samples could be successfully distinguished with one single method through the examination of these compounds’ retention times and their spectra acquired with a photodiode array detector. These results demonstrate that UHPLC analyses are extremely valuable for the acquisition of more precise chromatographic information concerning natural dyes with complex mixtures of different and/or closely related physicochemical properties, essential for distinguishing similar species of plants and animals used to colour cultural heritage objects.
Identification of American cochineal species (Dactylopius genus) can provide important informatio... more Identification of American cochineal species (Dactylopius genus) can provide important information for the study of historical works of art, entomology, cosmetics, pharmaceuticals and foods. In this study, validated species of Dactylopius, including the domesticated cochineal D. coccus, were analysed by high-performance
liquid chromatography with a diode array detector (HPLC-DAD) and submitted to multivariate data analysis, in order to discriminate the species and hence construct a reference library for a wide range of applications. Principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA)
models successfully provided accurate species classifications. This library was then applied to the identification of 72 historical insect specimens of unidentified species, mostly dating from the 19th
century, and belonging to the Economic Botany Collection, Royal Botanic Gardens, Kew, England. With this approach it was possible to identify anomalies in how insects were labelled historically, as several of them were revealed not to be cochineal. Nevertheless, more than 85% of the collection was determined to be species of Dactylopius and the majority of the specimens were identified as D. coccus. These results have shown that HPLC-DAD, in combination with suitable chemometric methods, is a powerful
approach for discriminating related cochineal species.
"The ARCHLAB Transnational Access, provided by the European Consortium CHARISMA project, grants t... more "The ARCHLAB Transnational Access, provided by the European Consortium CHARISMA project, grants the opportunity for carrying out research in the archives and laboratories of associated advanced facilities centres, from European Museums and Cultural Heritage Institutions. The possibility of being in touch with archives and researchers, from these European institutions, was very significant for the project TEXTILES, TRADE AND
TASTE, PORTUGAL AND THE WORLD (TTT), under development at the CHAM, FCSHUNL & UAç. The main aim of this project is the interdisciplinary study of historical textiles, by involving the work of a dozen of researchers from History, Chemistry and Conservation areas in Portugal. It currently comprises several sub-projects, which are especially focused on the historical and chemical study of ancient textiles, dating from 16th and 17th centuries.
The contact between TTT and CHARISMA projects was recently accomplished through the ARCHLAB Transnational Access, representing an important contribution for the development of Ana Serrano‘s PhD thesis, ―The Red Road of the Iberian Expansion:
Cochineal and the global dye trade‖. The invaluable visit to the Netherlands Cultural Heritage Agency (RCE), the National Gallery of London (NGL) and the British Museum (BM) allowed the exclusive contact with reports and databases concerning cochineal insect dyes and their analytical characterization in historical works of art, which is accomplished by specialized researchers at the advanced facilities from these institutions. This ARCHLAB Transnational Access grant revealed to be fundamental to acknowledge the research made on cochineal dyes until now, as it permitted a more definitive construction of the phases of this sub-project, which is described in detail below."
A new analytical approach based on high-performance liquid chromatography with diode array detect... more A new analytical approach based on high-performance liquid chromatography with diode array detector (HPLC-DAD) and multivariate data analysis was applied and assessed for analyzing the red dye extracted from cochineal insects, used in precious historical textiles. The most widely used method of analysis involves quantification of specific minor compounds (markers), using HPLC-DAD. However, variation in the cochineal markers concentration, use of aggressive dye extraction methods and poor resolution of HPLC chromatograms can compromise the identification of the precise insect species used in the textiles. In this study, a soft extraction method combined with a new dye recovery treatment was developed, capable of yielding HPLC chromatograms with good resolution, for the first time, for historical cochineal-dyed textiles. After principal components analysis (PCA) and mass spectrometry (MS), it was possible to identify the cochineal species used in these textiles, in contrast to the accepted method of analysis. In order to compare both methodologies, 7 cochineal species and 63 historical cochineal insect specimens were analyzed using the two approaches, and then compared with the results for 15 historical textiles in order to assess their applicability to real complex samples. The methodology developed here was shown to provide more accurate and consistent information than the traditional method. Almost all of the historical textiles were dyed with Porphyrophora sp. insects. These results emphasize the importance of adopting the proposed methodology for future research on cochineal (and related red dyes). Mild extraction methods and HPLC-DAD/MSn analysis yield distinctive profiles, which, in combination with a PCA reference database, are a powerful tool for identifying red insect dyes. Figure In pursuit of a precious red dye! A new methodology has been developed for determining the precise cochineal dye used in historical textiles. Mild extraction methods and HPLC-DAD yield distinctive profiles that, in combination with a dye reference database based on PCA, creates a powerful tool for identifying the precise red dye used. Surprisingly, almost all of the historical textiles analysed were not dyed with American cochineal.
Between the end of the 15th century and beginning of the 16th, the Portuguese and the Spanish exp... more Between the end of the 15th century and beginning of the 16th, the Portuguese and the Spanish expanded their empires to the Americas. While the Portuguese soon dedicated to the exploitation of brazilwood, the Spanish came to establish a monopoly in cochineal that would become one of the most important commercial products in the Atlantic until the 19th century. The interdisciplinary investigation presented here, combining Analytical Chemistry and Economic History, aims to explore the impact of the American insect as a commercial product in the global circulation of dyestuffs, and its importance as a red dye in the main centres of textile production in Europe and in Asia, in relation to other local insect dyes. The historical investigation comprised a comprehensive revision of historical publications and primary printed sources regarding the Iberian transatlantic trade in dyestuffs and their impact on European and Asian dyeing traditions during the Early Modern period. Special focus was given to the acceptance of American cochineal over local insect dye sources, namely kermes, lac and Armenian and Polish cochineal. This research reveals a gradual but clear adoption of the American dyestuff in Europe and in West Asia, although local insect dyes would still have a representative role in on-going practices, especially in East and Southeast Asia. Chemical research was pursued to evaluate the historical picture presented for the impact of the American dyestuff in Europe and, especially in Asia, to which insufficient historical information was available. Given that previous publications concerning the chemical characterization of insect dyes depicted limitations that compromised the differentiation of cochineal species in red-dyed historical textiles, an ultra high-performance liquid chromatography (UHPLC) method was optimized to deliver more accurate results. Then, experiments with cochineal and kermes dyes were undertaken following several dyeing parameters. The resulting dyed fibres were characterized with UHPLC, leading to meaningful insights about the behaviour of the colorants’ dye compounds. Subsequent artificial ageing of the dyed fibres and their characterization with mass spectrometry (MS) permitted to characterize, for the first time, photo-degradation compounds in the insect’s colorant. These results were reported to be similar to those for historical fibres and, for this reason, it became possible to compare the experimentally-dyed and historical fibres through partial-least squares discriminant analysis (PLS-DA), for the identification of the cochineal species used to colour the analysed historical fibres. By combining the results of this successful approach, along with the results for other coloured historical fibres and their contextualization with historical evidence, it was possible to ascribe assertive interpretations about the date and provenance of the investigated textiles. Moreover, successful historical interpretations could be obtained about the dynamics of American cochineal in European and Asian societies throughout the colonial period. Therefore, the interdisciplinary combination of chemical and statistical methods developed here, along with historical evidence, has proven to be an important approach that should be adopted in future projects for the characterization of insect dyes in cultural heritage objects.
"The identification of precise cochineal species used to dye historical textiles can provide impo... more "The identification of precise cochineal species used to dye historical textiles can provide important information about the provenance and date of these objects. The most widely used method to identify cochineal species in textiles involves quantification of specific minor compounds, after High-performance Liquid Chromatography with Diode Array Detection (HPLC/DAD) analysis. However, there are several factors which are not presently taken in account when characterizing cochineal species on historical textiles. Not only all the species of cochineal are not well studied, but also the current studies, based on a limited number of species, frequently face difficulties with the identification of these on historical textiles, especially due to the analysis conditions and the results treatment.
Therefore, a new approach on the study of cochineal species present in historical textiles was developed. Different parameters for the analysis conditions were undertaken to optimize the results for both insect species and textiles samples. Afterwards, with Principal Components Analysis (PCA), results from textiles samples exhibited a satisfactory correlation when compared with a cochineal reference database. Moreover, High-performance Liquid Chromatography with Diode Array Detector coupled with Mass Spectrometry (HPLC/DAD/MSn) analysis could offer accurate information on cochineal species and textiles samples. The characterization of six species of cochineal allowed, through PCA and HPLC/DAD/MSn analysis, the identification of unidentified cochineal insect samples and a group of Islamic and Italian historical dyed-cochineal textiles, dated from 15th to 17th centuries.
This identification contributes to connect the textiles’ history, and the trade and dyeing technologies on possible different species of cochineal. This fact regards especially textiles produced in the main textile centres, where, after the 16th century, the traded American cochineal was swiftly adopted, as many historical publications assert. Although this study identified American cochineal in a 17th-century Indian textile for the first time, the results for the other analyzed textiles did not reveal the presence of this species. In this way, the possibility of the prompt spread of the American specie in European and Asian textiles dyeing seems to be more complex than what is emphasized by present publications."
16th International Symposium on Wood and Furniture Conservation, Stichting Ebenist, 2024
An 18 th century, Dutch oak tabernacle with four, early 19th century silk brocade panels. The pan... more An 18 th century, Dutch oak tabernacle with four, early 19th century silk brocade panels. The panels line the inner walls and cover original decorative paper which was likely installed to mimic more expensive textiles until the material eventually was donated or otherwise acquired The silk panels were likely added shortly after the object's manufacture and may have originated from a clothing item, like a dress. A tabernacle's role and importance during religious ceremony is emphasized by material and aesthetic richness, created in this case by rich silk brocade. This mixed-media treatment aimed to stabilize the object and return it to its devotional state and potential display. The object will be used as a functioning tabernacle in Weesp, NL.
Darning is a collection of needlework techniques that can be used for mending damaged textiles, w... more Darning is a collection of needlework techniques that can be used for mending damaged textiles, while also functioning as camouflage or decoration. When used as a mending technique, darning repairs weakened areas, tears and holes by imitating the woven or knitted structure of the mended object, so that it appears intact. Pattern darning and surface darning are two darning techniques commonly used for the repair of woven textiles. While in Japan darning is routinely applied for conserving museum objects, in the rest of the world, this type of needle work tends to be generally excluded from textile conservation practices. The main arguments against its application include the relatively large amount of stitching ad the tension applied to the conserved object. However, these arguments tend to be based on sense-based experience, and no empirical analysis has yet been conducted on the impact of darning stitches on the mended object. This research aims to examine the extent to which darning can be considered an acceptable sewing technique within current conservation practices. For this, effectiveness (i.e. support that the technique can provide) and reversibility (i.e. the damages that the technique can cause to the conserved material) are assessed for basic form of pattern darning and surface darning by comparing them with laid-couching, the most commonly applied consolidation sewing technique in textile conservation. Two testing methods, tensile strength testing and fixed-load (hanging) testing were performed on fifteen modern taffeta silk samples per method, of which three were undamaged samples, three were damaged samples (artificially cut) and nine were conserved samples using the three needlework techniques under evaluation. With the tensile strength test, it was reported that surface darning delivered lower maximum sample elongation and higher breaking force than laid-couching, meaning that they are more effective. With the fixed-load test, constant force (~4Newton)was added to the samples in the course of fourteen days. The results showed that samples conserved with surface darning delivered the least weave distortion (i.e. dislocation of weave thread, which is at perpendicular direction to that of the added force), indicating its higher effectiveness. They also delivered the least stitch hole enlargement, indicating its higher reversibility, under the condition that the action of stitching itself does not pose a risk for the conserved material. Based on these results, it can be concluded that surface darning can demonstrate a higher effectiveness and reversibility than laid-couching. As for pattern darning, the results indicated similar response to that of laid-couching., Future research concerning pattern darning and its possible advantages over surface darning and laid-couching should be carried out, namely into the size and distribution of the stitches applied in textile conservation. Moreover, the potential of the efficacy of surface and pattern darning stitches in representative historical materials should be investigated.
An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that sank in the mi... more An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that sank in the mid-17th century, in the Wadden Sea, The Netherlands. A unique example of early modern fashion and artistry, it comprises about 300 textile fragments from costumes, parts of costumes and interior textiles, almost entirely made of silk and embroidered or woven with metal thread. Although buried for centuries, this finding is in very good condition, which might be related to the archaeological environment and the high quality of the fabrics. To assess the quality and historical background of these textiles, as well as their state of conservation for future preservation strategies, their materials have been characterized. A total of 218 textile yarns and metal threads were sampled from 34 fragments to 1) characterize the dyestuffs and mordants used, 2) to identify and evaluate the condition of the textile fibres, and 3) to assess the composition and condition of the metal threads. With ultra-high performance liquid chromatography coupled to diode array detector (UHPLC-PDA), it was verified that most fragments were coloured with insect dyes, and in some cases, madder and tannins as well. With research microscopy and scanning electron microscopy - energy dispersive x-ray spectrometer (SEM-EDX), silk fibres were mostly identified and these appeared clean, smooth and flexible; although those from more fragile fragments were evidently more friable and dirty, presenting pitting from biodegradation and contaminations from the archaeological environment. Silver sulphide crystals from the corrosion of silver were mostly observed on the metal threads, and gold was often detected, indicating that these were gilded. Even though the historical background of these fragments is still under investigation, it is undoubtedly clear that this is quite a lavish, unique finding that deserves to be fully appreciated and preserved for generations to come.
In-Between Textiles, 1400–1800 Weaving Subjectivities and Encounters, 2023
This chapter presents the results of a decade-long study on the appropriation of American cochine... more This chapter presents the results of a decade-long study on the appropriation of American cochineal in early modern European textile industries. The comparative study is based on in-depth archival research and a new scientific approach that allows, for the first time, the accurate distinction of insect dyes in historical textiles. Revealing the gradual adoption of New World dyestuff, the chapter shifts established narratives and calls for attention to the very material composition of in-between textiles. Actual matter inhabited these fabrics’ Third Space, whose material composition changed in response to early modern colonialism and consumerism.
Textiles, Trade & Taste: Portugal and the World (TTT) is a project that aspires to bring new syne... more Textiles, Trade & Taste: Portugal and the World (TTT) is a project that aspires to bring new synergies to the field of textile studies by promoting different connections and interdisciplinary approaches involving art history, materials science, and conservation. The TTT research network is based at the Center for Humanities in the School of Social Sciences and Humanities at the Universidade NOVA de Lisboa and organizes workshops, conferences, tours, and lectures in museums and research institutions. The network’s artistic and historical research has ranged from collating archival material to stylistic and iconographic studies, with the aim of placing textile objects in their historical, artistic, technological, and sociocultural contexts. Chemical analysis and characterization of dyes, textile fibers, and precious metal threads have provided important evidence for identifying the origins of raw materials and finished textiles, and for developing improved conservation treatments for their preservation for future generations. Recent research has examined the global circulation of dyes in the early modern period, especially reds, and also reconstructed the production and consumption of Indian, Chinese, and Portuguese embroideries and Islamic carpets. In 2011, TTT’s work led to the classification of three “Salting” carpets as national treasures in Portugal. The team members have collaborated with national and international museums, including Museu Nacional de Arte Antiga and Calouste Gulbenkian Museum (Lisbon), as well as Abegg-Stiftung (Riggisberg), The Metropolitan Museum of Art (New York), Musée des Tissus, (Lyon), Museum für Islamische Kunst (Berlin), Museum für angewandte Kunst (MAK) (Vienna), Rietberg Museum (Zürich), Rijksmuseum (Amsterdam), George Washington University Museum and The Textile Museum (Washington, D.C.), National Gallery of Art (Washington, D.C.), and Victoria and Albert Museum (London). The team’s art historians contributed to the platform “Museum With No Frontiers” to develop the online exhibition Discover Carpet Art involving Portuguese museums. TTT’s scientists have strong links with the Freer Gallery of Art and Arthur M. Sackler Gallery (National Museum of Asian Art, Washington, D.C.), University of Zaragoza (Spain), Rijksdienst voor het Cultureel Erfgoed (Cultural Heritage Agency of the Netherlands, Amersfoort), and the University of Amsterdam. We have been encouraged by the positive response of the international community to the results of our initial research projects.
tThe appraisal of the design and the weaving structure of Islamic knotted-pile carpets can tell p... more tThe appraisal of the design and the weaving structure of Islamic knotted-pile carpets can tell plentyabout the context in which they were produced, and the identification of signs of deterioration can helpto establish their condition. These are often somewhat imprecise and laborious examinations, especiallywhen considering carpets of large dimensions. Analytical methods that support these disciplines urgefurther exploration so that improved interpretations can be obtained.An interdisciplinary combination of art history, analytical science and textile conservation aimed, onthe one hand, to improve the weaving examination of these complex textile objects – by considering thespin of threads and the ply of yarns; the knot count and density; and the weaving structure of warps, weftsand piles – and on the other, to help their condition assessment – by mapping of damaged areas, old repairsand contaminations. For this purpose, the possibilities and limitations of several non-invasive imagingtechniques, namely transmitted, raking or incident visible, ultraviolet (UV) and infrared (IR) illuminationthrough Visual Spectral Comparator (VSC), as well as conventional X-radiography, mammography and(micro) CT scanning, were assessed to support the conventional visual examination of the weaving detailsand present condition of two 17th-century Safavid knotted-pile carpet fragments.Observation with NUV and NIR imaging with VSC, as well as CT techniques, offered enriching over-views about weaving characteristics, damaged areas or contaminations that were not easily discerniblewith the naked eye, thus supporting the conventional visual examination. As a result, detailed digitalmappings about the technological structure and the condition of the fragments could be obtained in arelatively efficient and accessible way. Moreover, combining art historical identification of the designwith the analysis of the weaving structure confirmed that both carpet fragments are border corners thatoriginally belonged to much larger carpets made in the so-called “Indo-Persian” style. The outcome ofthis interdisciplinary research brings very useful contributions for future art historical and conservationassessments of historical carpets, and it encourages further exploration of imaging techniques in theexamination of other textile objects in museums and private collections.
An exceptional group of silk fragments was unearthed in 2014 from a shipwreck, which sank in the ... more An exceptional group of silk fragments was unearthed in 2014 from a shipwreck, which sank in the mid-17th century, in the Wadden Sea, The Netherlands. A unique example of 17th-century fashion, it comprises about 300 textile fragments from garments, parts of garments and furnishing fabrics, almost entirely made of silk and embroidered or woven with metal thread. These are in remarkably good condition, which may be related to the archaeological environment, the quality of the silk yarns in the fragments, and the presence of metal threads and other metallic objects from the shipwreck. Surviving archaeological maritime silk textiles are extremely rare, which makes this a distinctive find posing challenges for selecting the most suitable conditions for exhibition and storage.
Scientific research was carried out with the aim to evaluate the response of modern and archaeological silks to temperature, relative humidity, light and oxygen, in order to define the most suitable parameters for the long-term storage and exhibition of the collection. Artificially aged samples taken from one of the archaeological fragments were analysed at the visual, structural and molecular level by means of colour measurements, Fourier transform infrared spectroscopy (FTIR) and ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FLD). The results showed that light exposure, in combination with high temperatures, oxygen and moisture strongly affected the silk's structure and molecular composition. Limiting exposure to light and removing oxygen reduced this effect and increased life expectancy significantly. Therefore, the analytical results obtained were essential to defining a preliminary preservation strategy for the collection: while on display, anoxic conditions slow down degradation of the silk by a factor of 4–5, whereas in a in dark storage, a low RH is the most important factor, with anoxic conditions providing additional reduction of decay.
Proceedings of the Natuurlijk Kleuren Symposium Nov. 2017, Textielcommissie, 2020
From the beginning of the 16th century, the Portuguese and the Spanish brought growing quantities... more From the beginning of the 16th century, the Portuguese and the Spanish brought growing quantities of dyes from the Americas to Europe, namely cochineal, indigo, brazilwood and logwood. All these enjoyed increasing positions in transatlantic shipments, particularly cochineal, which ranked in price after silver and gold in Spanish cargoes. Later in the century, the Dutch, English and French also entered the transatlantic trade and, subsequently, American dyes no longer passed exclusively through the Iberian Peninsula.
Once in Europe, American dyes had a decisive impact on long-established dyeing traditions. Not only they allowed a wider range of colours, but they were also economically advantageous over European dyes. For instance, cochineal and indigo presented higher contents of colorant in relation to related local dyes, which allowed for larger numbers of cloth to be coloured. Hence, they were soon assimilated in the main European centres of textile production. However, in some regions, textile producers continued to prefer local dyes over the new ones.
An interdisciplinary investigation explored the diverse response of European territories to the trade and assimilation of American dyes in the textile centres, during the 16th and the 17th centuries. By combining historical research and chemical analyses of colorants in historical textiles, it was revealed that this process seems to have happened gradually, with more or less resistance, depending on the political and economic circumstances of each territory.
In de zomer van 2014 is een grote collectie 17de-eeuws textiel gevonden in een scheepswrak bij Te... more In de zomer van 2014 is een grote collectie 17de-eeuws textiel gevonden in een scheepswrak bij Texel. De collectie is overgedragen aan Museum Kaap Skil te Texel en is later naar de rechtmatige eigenaar, de Provincie Noord-Holland, gegaan. In het najaar van 2015 is contact gezocht met de Universiteit van Amsterdam, conservering en restauratie van cultureel erfgoed (UvA-C&R) om mee te helpen met het beheer en behoud van het textiel.
The colorant behaviour of cochineal and kermes insect dyes in 141 experimentally-dyed and 28 arti... more The colorant behaviour of cochineal and kermes insect dyes in 141 experimentally-dyed and 28 artificially-aged samples of silk and wool was investigated using ultra-high performance liquid chromatography coupled to photodiode array detector (UHPLC-PDA), liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS) and image scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDX). Partial-least squares discriminant analysis (PLS-DA) was then used to model the acquired UHPLC-PDA data and assess the possibility of discriminating cochineal insect species, as well as their correspondent dyed and aged reference fibres. The resulting models helped to characterize a set of 117 red samples from 95 historical textiles, in which UHPLC-PDA analyses have reported the presence of cochineal and kermes insect dyes.
Analytical investigation of the experimentally-dyed and artificially-aged fibres has demonstrated that the ratio of compounds in the insects dye composition can change, depending on the dyeing conditions applied and the type of fibres used. Similarities were observed when comparing the UHPLC-MS and SEM-EDX results from the dyed and aged references with the historical samples. This was verified with PLS-DA models of the chromatographic data, facilitating the classification of the cochineal species present in the historical samples. The majority of these samples were identified to contain American cochineal, which is in agreement with historical and dye identification literature that describe the impact of this dyestuff into European and Asian dyeing practices, after the Iberian Expansion in the 16th century.
The analytical results emphasize the importance of using statistical data interpretation for the discrimination of cochineal dyes, besides qualitative and quantitative evaluation of chromatograms. Hence, the combination of UHPLC-PDA with a statistical classification method, such as PLS-DA, has been demonstrated to be an advisable approach in future investigations to assess closely related species of natural dyes in historical textile samples. This is particularly important when aiming to achieve more accurate interpretations about the history of works of art, or the application of natural dyes in old textile production.
Catharijne - Magazine van Museum Catharijneconvent: Het geheim van de Middeleeuwen in gouddraad en zijde
In het kader van het project The Red Road of the Iberian Expansion: Cochineal and the Global Dye ... more In het kader van het project The Red Road of the Iberian Expansion: Cochineal and the Global Dye Trade zijn de oorspronkelijke kleuren van historisch textiel uit de collectie van Museum Catharijneconvent bestudeerd. Het doel hiervan was om het gebruik van lokale en geïmporteerde kleurstoffen, in de Europese verfindustrie in de overgangsperiode van de late Middeleeuwen naar de nieuwe tijd, te achterhalen, met name de kleurstof afkomstig van de Cochenille luis.
In the framework of the project “THE RED ROAD OF THE IBERIAN EXPANSION: Cochineal and the Global Dye Trade”, the colours of historical textiles belonging to the Catharijnconvent museum collection were studied to assess the use of local and faraway- imported sources of colour, especially cochineal, into the European dyeing industry, in the transition between the Middle Ages and the beginning of the Age of Discoveries.
An evaluation was undertaken of ultrahigh pressure liquid chromatography (UHPLC) in comparison to... more An evaluation was undertaken of ultrahigh pressure liquid chromatography (UHPLC) in comparison to high-performance liquid chromatography (HPLC) for characterizing natural dyes in cultural heritage objects. A new UHPLC method was optimized by testing several analytical parameters adapted from prior UHPLC studies developed in diverse fields of research. Different gradient elution programs were tested on seven UHPLC columns with different dimensions and stationary phase compositions by applying several mobile phases, flow rates, temperatures, and runtimes. The UHPLC method successfully provided more improved data than that achieved by the HPLC method. Indeed, even though carminic acid has shown circa 146% higher resolution with HPLC, UHPLC resulted in an increase of 41 to 61% resolution and a decrease of 91 to 422% limit of detection, depending on the dye compound. The optimized method was subsequently assigned to analyse 59 natural reference materials, in which 85 different components were ascribed with different physicochemical properties, in order to create a spectral database for future characterization of dyes in cultural heritage objects. The majority of these reference samples could be successfully distinguished with one single method through the examination of these compounds’ retention times and their spectra acquired with a photodiode array detector. These results demonstrate that UHPLC analyses are extremely valuable for the acquisition of more precise chromatographic information concerning natural dyes with complex mixtures of different and/or closely related physicochemical properties, essential for distinguishing similar species of plants and animals used to colour cultural heritage objects.
Identification of American cochineal species (Dactylopius genus) can provide important informatio... more Identification of American cochineal species (Dactylopius genus) can provide important information for the study of historical works of art, entomology, cosmetics, pharmaceuticals and foods. In this study, validated species of Dactylopius, including the domesticated cochineal D. coccus, were analysed by high-performance
liquid chromatography with a diode array detector (HPLC-DAD) and submitted to multivariate data analysis, in order to discriminate the species and hence construct a reference library for a wide range of applications. Principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA)
models successfully provided accurate species classifications. This library was then applied to the identification of 72 historical insect specimens of unidentified species, mostly dating from the 19th
century, and belonging to the Economic Botany Collection, Royal Botanic Gardens, Kew, England. With this approach it was possible to identify anomalies in how insects were labelled historically, as several of them were revealed not to be cochineal. Nevertheless, more than 85% of the collection was determined to be species of Dactylopius and the majority of the specimens were identified as D. coccus. These results have shown that HPLC-DAD, in combination with suitable chemometric methods, is a powerful
approach for discriminating related cochineal species.
"The ARCHLAB Transnational Access, provided by the European Consortium CHARISMA project, grants t... more "The ARCHLAB Transnational Access, provided by the European Consortium CHARISMA project, grants the opportunity for carrying out research in the archives and laboratories of associated advanced facilities centres, from European Museums and Cultural Heritage Institutions. The possibility of being in touch with archives and researchers, from these European institutions, was very significant for the project TEXTILES, TRADE AND
TASTE, PORTUGAL AND THE WORLD (TTT), under development at the CHAM, FCSHUNL & UAç. The main aim of this project is the interdisciplinary study of historical textiles, by involving the work of a dozen of researchers from History, Chemistry and Conservation areas in Portugal. It currently comprises several sub-projects, which are especially focused on the historical and chemical study of ancient textiles, dating from 16th and 17th centuries.
The contact between TTT and CHARISMA projects was recently accomplished through the ARCHLAB Transnational Access, representing an important contribution for the development of Ana Serrano‘s PhD thesis, ―The Red Road of the Iberian Expansion:
Cochineal and the global dye trade‖. The invaluable visit to the Netherlands Cultural Heritage Agency (RCE), the National Gallery of London (NGL) and the British Museum (BM) allowed the exclusive contact with reports and databases concerning cochineal insect dyes and their analytical characterization in historical works of art, which is accomplished by specialized researchers at the advanced facilities from these institutions. This ARCHLAB Transnational Access grant revealed to be fundamental to acknowledge the research made on cochineal dyes until now, as it permitted a more definitive construction of the phases of this sub-project, which is described in detail below."
A new analytical approach based on high-performance liquid chromatography with diode array detect... more A new analytical approach based on high-performance liquid chromatography with diode array detector (HPLC-DAD) and multivariate data analysis was applied and assessed for analyzing the red dye extracted from cochineal insects, used in precious historical textiles. The most widely used method of analysis involves quantification of specific minor compounds (markers), using HPLC-DAD. However, variation in the cochineal markers concentration, use of aggressive dye extraction methods and poor resolution of HPLC chromatograms can compromise the identification of the precise insect species used in the textiles. In this study, a soft extraction method combined with a new dye recovery treatment was developed, capable of yielding HPLC chromatograms with good resolution, for the first time, for historical cochineal-dyed textiles. After principal components analysis (PCA) and mass spectrometry (MS), it was possible to identify the cochineal species used in these textiles, in contrast to the accepted method of analysis. In order to compare both methodologies, 7 cochineal species and 63 historical cochineal insect specimens were analyzed using the two approaches, and then compared with the results for 15 historical textiles in order to assess their applicability to real complex samples. The methodology developed here was shown to provide more accurate and consistent information than the traditional method. Almost all of the historical textiles were dyed with Porphyrophora sp. insects. These results emphasize the importance of adopting the proposed methodology for future research on cochineal (and related red dyes). Mild extraction methods and HPLC-DAD/MSn analysis yield distinctive profiles, which, in combination with a PCA reference database, are a powerful tool for identifying red insect dyes. Figure In pursuit of a precious red dye! A new methodology has been developed for determining the precise cochineal dye used in historical textiles. Mild extraction methods and HPLC-DAD yield distinctive profiles that, in combination with a dye reference database based on PCA, creates a powerful tool for identifying the precise red dye used. Surprisingly, almost all of the historical textiles analysed were not dyed with American cochineal.
Between the end of the 15th century and beginning of the 16th, the Portuguese and the Spanish exp... more Between the end of the 15th century and beginning of the 16th, the Portuguese and the Spanish expanded their empires to the Americas. While the Portuguese soon dedicated to the exploitation of brazilwood, the Spanish came to establish a monopoly in cochineal that would become one of the most important commercial products in the Atlantic until the 19th century. The interdisciplinary investigation presented here, combining Analytical Chemistry and Economic History, aims to explore the impact of the American insect as a commercial product in the global circulation of dyestuffs, and its importance as a red dye in the main centres of textile production in Europe and in Asia, in relation to other local insect dyes. The historical investigation comprised a comprehensive revision of historical publications and primary printed sources regarding the Iberian transatlantic trade in dyestuffs and their impact on European and Asian dyeing traditions during the Early Modern period. Special focus was given to the acceptance of American cochineal over local insect dye sources, namely kermes, lac and Armenian and Polish cochineal. This research reveals a gradual but clear adoption of the American dyestuff in Europe and in West Asia, although local insect dyes would still have a representative role in on-going practices, especially in East and Southeast Asia. Chemical research was pursued to evaluate the historical picture presented for the impact of the American dyestuff in Europe and, especially in Asia, to which insufficient historical information was available. Given that previous publications concerning the chemical characterization of insect dyes depicted limitations that compromised the differentiation of cochineal species in red-dyed historical textiles, an ultra high-performance liquid chromatography (UHPLC) method was optimized to deliver more accurate results. Then, experiments with cochineal and kermes dyes were undertaken following several dyeing parameters. The resulting dyed fibres were characterized with UHPLC, leading to meaningful insights about the behaviour of the colorants’ dye compounds. Subsequent artificial ageing of the dyed fibres and their characterization with mass spectrometry (MS) permitted to characterize, for the first time, photo-degradation compounds in the insect’s colorant. These results were reported to be similar to those for historical fibres and, for this reason, it became possible to compare the experimentally-dyed and historical fibres through partial-least squares discriminant analysis (PLS-DA), for the identification of the cochineal species used to colour the analysed historical fibres. By combining the results of this successful approach, along with the results for other coloured historical fibres and their contextualization with historical evidence, it was possible to ascribe assertive interpretations about the date and provenance of the investigated textiles. Moreover, successful historical interpretations could be obtained about the dynamics of American cochineal in European and Asian societies throughout the colonial period. Therefore, the interdisciplinary combination of chemical and statistical methods developed here, along with historical evidence, has proven to be an important approach that should be adopted in future projects for the characterization of insect dyes in cultural heritage objects.
"The identification of precise cochineal species used to dye historical textiles can provide impo... more "The identification of precise cochineal species used to dye historical textiles can provide important information about the provenance and date of these objects. The most widely used method to identify cochineal species in textiles involves quantification of specific minor compounds, after High-performance Liquid Chromatography with Diode Array Detection (HPLC/DAD) analysis. However, there are several factors which are not presently taken in account when characterizing cochineal species on historical textiles. Not only all the species of cochineal are not well studied, but also the current studies, based on a limited number of species, frequently face difficulties with the identification of these on historical textiles, especially due to the analysis conditions and the results treatment.
Therefore, a new approach on the study of cochineal species present in historical textiles was developed. Different parameters for the analysis conditions were undertaken to optimize the results for both insect species and textiles samples. Afterwards, with Principal Components Analysis (PCA), results from textiles samples exhibited a satisfactory correlation when compared with a cochineal reference database. Moreover, High-performance Liquid Chromatography with Diode Array Detector coupled with Mass Spectrometry (HPLC/DAD/MSn) analysis could offer accurate information on cochineal species and textiles samples. The characterization of six species of cochineal allowed, through PCA and HPLC/DAD/MSn analysis, the identification of unidentified cochineal insect samples and a group of Islamic and Italian historical dyed-cochineal textiles, dated from 15th to 17th centuries.
This identification contributes to connect the textiles’ history, and the trade and dyeing technologies on possible different species of cochineal. This fact regards especially textiles produced in the main textile centres, where, after the 16th century, the traded American cochineal was swiftly adopted, as many historical publications assert. Although this study identified American cochineal in a 17th-century Indian textile for the first time, the results for the other analyzed textiles did not reveal the presence of this species. In this way, the possibility of the prompt spread of the American specie in European and Asian textiles dyeing seems to be more complex than what is emphasized by present publications."
16th International Symposium on Wood and Furniture Conservation, Stichting Ebenist, 2024
An 18 th century, Dutch oak tabernacle with four, early 19th century silk brocade panels. The pan... more An 18 th century, Dutch oak tabernacle with four, early 19th century silk brocade panels. The panels line the inner walls and cover original decorative paper which was likely installed to mimic more expensive textiles until the material eventually was donated or otherwise acquired The silk panels were likely added shortly after the object's manufacture and may have originated from a clothing item, like a dress. A tabernacle's role and importance during religious ceremony is emphasized by material and aesthetic richness, created in this case by rich silk brocade. This mixed-media treatment aimed to stabilize the object and return it to its devotional state and potential display. The object will be used as a functioning tabernacle in Weesp, NL.
Darning is a collection of needlework techniques that can be used for mending damaged textiles, w... more Darning is a collection of needlework techniques that can be used for mending damaged textiles, while also functioning as camouflage or decoration. When used as a mending technique, darning repairs weakened areas, tears and holes by imitating the woven or knitted structure of the mended object, so that it appears intact. Pattern darning and surface darning are two darning techniques commonly used for the repair of woven textiles. While in Japan darning is routinely applied for conserving museum objects, in the rest of the world, this type of needle work tends to be generally excluded from textile conservation practices. The main arguments against its application include the relatively large amount of stitching ad the tension applied to the conserved object. However, these arguments tend to be based on sense-based experience, and no empirical analysis has yet been conducted on the impact of darning stitches on the mended object. This research aims to examine the extent to which darning can be considered an acceptable sewing technique within current conservation practices. For this, effectiveness (i.e. support that the technique can provide) and reversibility (i.e. the damages that the technique can cause to the conserved material) are assessed for basic form of pattern darning and surface darning by comparing them with laid-couching, the most commonly applied consolidation sewing technique in textile conservation. Two testing methods, tensile strength testing and fixed-load (hanging) testing were performed on fifteen modern taffeta silk samples per method, of which three were undamaged samples, three were damaged samples (artificially cut) and nine were conserved samples using the three needlework techniques under evaluation. With the tensile strength test, it was reported that surface darning delivered lower maximum sample elongation and higher breaking force than laid-couching, meaning that they are more effective. With the fixed-load test, constant force (~4Newton)was added to the samples in the course of fourteen days. The results showed that samples conserved with surface darning delivered the least weave distortion (i.e. dislocation of weave thread, which is at perpendicular direction to that of the added force), indicating its higher effectiveness. They also delivered the least stitch hole enlargement, indicating its higher reversibility, under the condition that the action of stitching itself does not pose a risk for the conserved material. Based on these results, it can be concluded that surface darning can demonstrate a higher effectiveness and reversibility than laid-couching. As for pattern darning, the results indicated similar response to that of laid-couching., Future research concerning pattern darning and its possible advantages over surface darning and laid-couching should be carried out, namely into the size and distribution of the stitches applied in textile conservation. Moreover, the potential of the efficacy of surface and pattern darning stitches in representative historical materials should be investigated.
An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that sank in the mi... more An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that sank in the mid-17th century, in the Wadden Sea, The Netherlands. A unique example of early modern fashion and artistry, it comprises about 300 textile fragments from costumes, parts of costumes and interior textiles, almost entirely made of silk and embroidered or woven with metal thread. Although buried for centuries, this finding is in very good condition, which might be related to the archaeological environment and the high quality of the fabrics. To assess the quality and historical background of these textiles, as well as their state of conservation for future preservation strategies, their materials have been characterized. A total of 218 textile yarns and metal threads were sampled from 34 fragments to 1) characterize the dyestuffs and mordants used, 2) to identify and evaluate the condition of the textile fibres, and 3) to assess the composition and condition of the metal threads. With ultra-high performance liquid chromatography coupled to diode array detector (UHPLC-PDA), it was verified that most fragments were coloured with insect dyes, and in some cases, madder and tannins as well. With research microscopy and scanning electron microscopy - energy dispersive x-ray spectrometer (SEM-EDX), silk fibres were mostly identified and these appeared clean, smooth and flexible; although those from more fragile fragments were evidently more friable and dirty, presenting pitting from biodegradation and contaminations from the archaeological environment. Silver sulphide crystals from the corrosion of silver were mostly observed on the metal threads, and gold was often detected, indicating that these were gilded. Even though the historical background of these fragments is still under investigation, it is undoubtedly clear that this is quite a lavish, unique finding that deserves to be fully appreciated and preserved for generations to come.
Natural organic dyes from diverse species of plants and animals have been widely characterized in... more Natural organic dyes from diverse species of plants and animals have been widely characterized in cultural heritage objects using high-performance liquid chromatography (HPLC). As these dyes generally comprise very complex and polar matrixes of compounds and minor compounds, such as flavonoids, anthraquinones or indigoids, with different and/or similar physicochemical properties, chromatographic resolution has become a major concern. In this study, a new ultra high-performance liquid chromatography (UHPLC) was optimized to characterize a wide range of natural dyes usually reported in cultural heritage objects. Several analytical parameters were tested on seven UHPLC columns with different dimensions and stationary phase compositions and, subsequently, the optimized method was compared with a conventional HPLC method, which has been widely applied to identify natural dyes in cultural heritage objects. The former method could successfully provide more improved data than that achieved by the latter, displaying higher chromatographic resolution as well as a better limit of detection. Therefore, a spectral database was created with 59 natural reference materials with different and/or similar physicochemical properties using the optimized UHPLC method. The majority of these reference samples could be distinguished in one single analysis through the examination of the compounds retention time and the spectra acquired with a photodiode array detector. Such a powerful approach has demonstrated to be extremely valuable for the acquisition of more precise chromatographic information concerning natural organic dyes and, for this reason, it is highly recommendable to perform future dye identification in the field of cultural heritage.
An interdisciplinary project that connects both disciplines of History and Chemistry has been dev... more An interdisciplinary project that connects both disciplines of History and Chemistry has been developed in order to obtain accurate approaches on the real impact of American cochineal, as a red dyestuff, in European and Asian centres of textile production, between the 16th and 18th centuries. This will be achieved through the revision of historical sources, along with the development of an optimized analytical method, which comprises the chromatographic analysis of cochineal species and their subsequent differentiation with multivariate statistical comparison and, consequently, their further characterization in European and Asian historical textiles, dated from the 16th century onwards.
It has been previously shown that High-Performance Liquid Chromatography (HPLC), along with components quantification, cannot provide a precise characterization of the cochineal insect species, and for this reason, multivariate statistical analyses are needed to compare the resulting chromatograms [1]. As good resolution chromatograms are required to ensure the correct discrimination of the components present in cochineal species, it was opted to undertake an optimization of the analysis conditions using Ultra high-Performance Liquid Chromatography (UPLC). This very recent technique presents several advantages over HPLC, as it can provide a better resolution, owing to the smaller particle size columns [2], essential for the low molecular weight from dyestuff components. Therefore, the optimization of the analytical conditions comprised three main parameters: several UPLC columns of different dimensions and stationary phase composition; different elution gradients, adapted from previously published HPLC methods used for dyestuffs characterization [3]; and mixtures of natural dyestuffs extracts, which included the main components commonly found in historical textiles. The optimized elution method for UPLC was then applied to a HPLC column, hence demonstrating that UPLC analyses provide more accurate results than HPLC. Indeed, the Limit of Detection (LOD) significantly improved with UPLC, which allowed the acquisition of more precise data, extremely valuable for the characterization of minor components present in dyestuffs. Therefore, this research is of upmost importance, as it represents the first application of UPLC analyses into the field of dyestuff analysis related to cultural heritage.
[1] Serrano, Ana, Sousa, Micaela M., Hallett, Jessica, Lopes, João A., Oliveira, M. Conceição, “Analysis of natural red dyes (cochineal) in textiles of historical importance using HPLC and multivariate data analysis”, Analytical and Bioanalytical Chemistry, 401 (2011) 735-743.
[2] Guillarme, D., Ruta, J., Rudaz, S., Veuthey, J., “New trends in fast and high-resolution liquid chromatography : a critical comparison of existing approaches”, Analytical and Bioanalytical Chemistry, 397 (2010) 1069-1082.
[3] Joosten, Ineke, van Bommel, Maarten, “Critical evaluation of micro-chemical analysis of archaeological materials”, Microchimica Acta, 162 (2008), 433-466.
An exceptional group of silk fabrics was lifted in 2014 from a shipwreck that sank in the mid-17t... more An exceptional group of silk fabrics was lifted in 2014 from a shipwreck that sank in the mid-17th century, in the Wadden Sea, The Netherlands. It comprises about 300 textiles, both fragments, and complete garments almost entirely made of silk and embroidered or woven with metal thread. To assess their quality and historical background, the style and the weave structure of the fabrics were examined. Moreover, the dyestuffs and mordants in the yarns and the metal threads were characterised, leading to important interpretations about the quality and the condition of the fragments. Many crimson fragments, including velvets and brochés, were found to have been coloured with insect dyes, whereas gold and gilt-silver were detected in the metal threads of many exquisitely embroidered or brocaded fragments. Although this collection's historical background is still under investigation, it is clear that this is a lavish finding that deserves full recognition.
The Natural Dyes of the Americas: A Forgotten Chapter in the History of the International Economy, 16th-19th Centuries - XIX World Economic History Congress, 2022
Dressing the Early Modern Conference: Contributions of Science and Technology to the Study of Early Modern Dress, 2019
Islamic knotted-pile carpets are remarkable art objects and rich historical sources in museums ar... more Islamic knotted-pile carpets are remarkable art objects and rich historical sources in museums around the world. The study of their complex characteristics can tell plenty about the date, the context and the societies in which they were produced. Art historians usually focus on the visual observation of their design and weaving structure, but this can be a rather subjective and laborious examination. Analytical methods that enhance this approach urge further exploration, so that more accurate art historical interpretations can be obtained. The interdisciplinary CarpetACT project combines art history with analytical and data sciences, with the aim to improve the weaving examination of these complex carpets, by considering the spin of threads; the ply and twist of yarns; the thread count and density; and the weaving structure of warps, wefts and piles. Several non-invasive analytical techniques, namely video spectral comparator (VSC), X-radiography, tomography and (micro) CT scanning are tested to assess a small group of 16th- and 17th-century Islamic knotted-pile carpets or fragments of these objects, belonging to the Rijksmuseum collection. Machine-learning methods are developed to process and compare digital photographs from these objects and a large quantity of data obtained with the tested analytical techniques. Ultimately, the outcome of this approach is compared with the results obtained with the traditional technical examination based on visual observations of the carpets. Within this feasibility study, it has been possible to highlight the possibilities and limitations of the tested imaging techniques, and the potential of data science to enhance the interpretation process of their results. Indeed, this approach has enabled to identify technological details about the carpets’ weaving structure, as well as about their present condition and past restorations that passed unnoticed with the traditional technical examination. Therefore, the outcome of this research brings unprecedented contributions to art historical and conservation research and, in particular, to the future of the technological study of historical textiles.
ICOM-CC Textiles Working Group Interim Meeting, A Challenging Dimension: The Conservation and Research of Costume and Accessories, 2019
An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that had sunk in th... more An exceptional group of silk fragments was unearthed in 2014 from a shipwreck that had sunk in the mid-17th century, in the Wadden Sea, The Netherlands. A unique example of 17th-century fashion, it comprises about 300 textile fragments from costumes, parts of costumes and interior textiles, almost entirely made of silk and embroidered or woven with metal thread. These are in remarkably good condition, which might be related to the archaeological environment and the high quality of the fabrics. Surviving archaeological maritime silk textiles are extremely rare, which makes this a distinctive finding; although it also poses challenges to museum curators when selecting the most suitable conditions to exhibit and store this type of objects. Aiming at the long-term preservation of this collection, a set of archaeological silk samples, along with modern silk standards, were submitted to different ageing setups to understand their response to common deterioration parameters in a museum environment: temperature, relative humidity, light and oxygen. The experimentally-aged results were submitted to a systematic assessment at the visual, structural and molecular levels, by means of colour measurements, fourier transform infrared spectroscopy (FTIR) and ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FLD). This research was invaluable to appraise the present condition of the archaeological maritime silk and to understand its response to artificial ageing. Indeed, it was possible to conclude that light exposure, in combination with high temperatures, oxygen and moisture highly affected silk's structure and composition. However, when limiting exposure from oxygen and light, life expectancy significantly increased, and small changes were verified. Eventually, the conclusions obtained in this study will be essential to defining the most suitable strategy to preserve the collection inside the storage and display cases of the museum, allowing its longer accessibility to the general and specialized public.
Vanaf het begin van de 16e eeuw, brachten de Portugezen en de Spanjaarden groeiende hoeveelheden ... more Vanaf het begin van de 16e eeuw, brachten de Portugezen en de Spanjaarden groeiende hoeveelheden kleurstoffen vanuit Amerika naar Europa, met name cochenilleluis, indigo, brazielhout en blauwhout. Deze kleurstoffen hadden een belangrijke positie in de transatlantische handel. Vooral cochenille, het meest kostbare product aan boord van de Spanjaarden na zilver en goud. Later in de eeuw voerden ook de Nederlanders, Engelsen en Fransen in de transatlantische handel, waarna Amerikaanse kleurstoffen niet langer uitsluitend via het Iberisch Schiereiland liepen.
Eens in Europa, hadden deze kleurstoffen een beslissende invloed op oude verftradities. Niet alleen creërden ze een breder assortiment aan kleuren, maar ook waren ze economisch voordeliger dan de Europese kleurstoffen. Zo bevatten cochenille en indigo een hoger gehalte aan kleurstof in vergelijking met verwante lokale kleurstoffen en hierdoor kon er meer kleren geverft worden met dezelfde hoeveelheid. Desalniettemin, vervolgden de stoffenververs het gebruik van traditionele kleurstoffen in bepaalde regio´s.
Een interdisciplinair onderzoek is uitgevoerd naar de Europese reactie en assimilatie van de Amerikaanse kleurstoffen in 16e en 17e eeuwse textielcentra. Historisch onderzoek en chemische analyses van kleur in historische textielen hebben aangetoond dat dit proces langzaam op gang kwam met enige weerstand, afhankelijk van politieke en economische omstandigheden van elk gebied.
In 2014, a large collection of textile fragments was found in a 17th-century shipwreck (named BZN... more In 2014, a large collection of textile fragments was found in a 17th-century shipwreck (named BZN17) that had sunk in the Wadden Sea, near the island of Texel, The Netherlands. Captured in a time capsule for centuries, this collection represents a unique example of 17th century fashion, comprising over 150 textile fragments, including costumes, parts of costumes and interior textiles. Although buried for centuries, they are in remarkably good condition, which might be related to the archaeological environment and the high quality of the fabrics. Indeed, these are almost entirely made of silk (except one woollen carpet), and embroidered or woven with metal thread. The most striking characteristic of this collection is the well-preserved deep red colour displayed by many of the textiles.
To understand the origin and function of these textiles, as well as their state of conservation for future preservation strategies, it was important to characterize their materials. Hence, a group of 12 objects was selected for evaluation with ultra-high performance liquid chromatography with diode array detector (UHPLC-PDA) and a scanning electron microscope coupled to an energy dispersive x-ray spectrometer (SEM-EDX).
With UHPLC-PDA, coccid insect dyes were identified as the main colorants on the textiles. However, the ratio of their dye compounds seems to have been affected by the maritime archaeological conditions: dcII and flavokermesic acid were not reported in any of the textiles; and an unusually high kermesic acid equivalent was detected, in relation to the major compounds kermesic and carminic acids. Even though American cochineal and kermes could be possibly attributed in some cases, these results substantially hinder the precise identification of the insect sources. Besides these, madder was often found mixed with the insect dyes or in textile parts that are not directly visible on the costumes.
The evaluation of the fibres with SEM-EDX indicated that some fibres show evidence of microorganism attack, and that the majority has preserved their flexibility; although those from fabrics of lower quality (e.g. lining) are more friable. On the metal threads, silver sulphide crystals were observed, and these correspond to the degradation product of silver. Also, gold was detected on few threads, which indicates that they were probably gilded. Due to the corrosion of silver, most gold particles could have been lost in the maritime environment.
While the provenance of these textiles, and the ship that carried them, is still under investigation, the analytical results obtained undoubtedly prove that a very rich finding has been unearthed. Nevertheless, the archaeological conditions certainly had a preponderant influence on their original appearance and this deserves future research.
A multidisciplinary investigation, combining History, textile objects from museum collections, an... more A multidisciplinary investigation, combining History, textile objects from museum collections, and Chemistry, aimed to explore the impact of cochineal as a commercial product in the global circulation of dyestuffs, and its importance in the main centres of textile production in Europe and in Asia. The outcome brought assertive interpretations about the investigated textiles and the dynamics of American cochineal in European and Asian societies. This approach has shown to be a recommendable methodology to adopt in future projects for the characterization of insect dyes in cultural heritage objects.
Up until the end of the medieval period, the most extravagant, brilliant and enduring crimson red... more Up until the end of the medieval period, the most extravagant, brilliant and enduring crimson red fabrics were dyed with valuable insect dyes: kermes, lac dye and Polish and Armenian cochineal. Symbols of hierarchy and power, crimson textiles were very difficult to obtain, owing to the complex and costly dyeing processes involved and to the scarcity of insects. These were collected in certain parts of Europe and Asia, and traded through well-established commercial routes to reach the main European cloth-producing centres. With the Iberian Expansion in the 16th century, the Spanish began exporting American cochineal from Mexico. Richer in red colorant than other insect dyes, it achieved great success among textile manufacturers, bringing enormous financial profit to the Spanish Empire 1. Publications over the last century have affirmed that as soon as the American insect started appearing in Europe, it rapidly penetrated textile workshops and fashion, replacing other local insect sources 2. A multidisciplinary study-combining history, textile objects from museum collections, and chemistry-was developed to explore the impact of American cochineal in European centres of textile production, in relation to traditional dyes 3. After a comprehensive revision of historical sources, chemical investigation was undertaken to determine the red colorants used in luxurious European historical textile objects, dating from the 15th to 17th centuries. Since analytical limitations verified in previous works compromised the chemical characterization of cochineal dyes 4 , a new methodology comprising UHPLC (ultra high-performance liquid chromatography) and multivariate statistical analysis was carried out to obtain precise knowledge of the dyes present in the historical textiles 5. The successful results of this approach offer more accurate information about the historical context of the dyed textiles, and thus, more conclusive interpretations about the history of the trade and consumption of insect dyes used in European textiles and clothing, during the Late Medieval and Early Modern periods.
An interdisciplinary project that connects both disciplines of History and Chemistry has been dev... more An interdisciplinary project that connects both disciplines of History and Chemistry has been developed in order to attain accurate approaches on the impact of American cochineal as a red dyestuff in European and Asian textile production centres between the 16th and 18th centuries, in contrast to other locally-available red dye sources like kermes or Polish and Armenian cochineal insects.
Given the similar colorant composition of these red dye sources, a characterization study was performed on textile samples to assess possible modifications that can lead to a more accurate knowledge of their presence in historical textiles. Based on the work performed by Golikov [1,2], as well as other contemporary studies and historical recipes dated between the 15th and 18th centuries, several parameters for dyeing crimson were tested on silk and wool with American cochineal. Therefore, the influence of the pH, temperature, duration and the addition of ingredients such as soap, cream of tartar or turmeric were assessed. Then, the parameters that suited the best shades of crimson were selected to dye with kermes, Armerian and Polish cochineal.
Subsequently, the dyed samples were analyzed with ultrahigh pressure liquid chromatography coupled to a photodiode array detector (UHPLC-PDA) [3] and the chromatograms were analysed qualitatively and quantitatively with multivariate statistical data analysis methods [4]. The methodology developed demonstrated that it is possible to obtain consistent information about dyed samples and their composition, according to the experimental parameters and the textile substrate used. Along with the revision of historical sources for dyeing, this study has brought invaluable contributions to the study of cochineal and kermes insect sources used to dye historical textile samples, as well as to the historical evaluation of the incorporation of American cochineal into European and Asian dyeing traditions, from the 16th century onwards.
"Natural red dyes have long been associated with power and extravagance, asthey were always expen... more "Natural red dyes have long been associated with power and extravagance, asthey were always expensive to acquire and the dyeing process was complex and required highly specialized
knowledge. Until the end of the 15th century, different species of Porphyrophora cochineal insects were collected and extensively traded throughout Europe and Asia. However, with the
Iberian Expansion at the beginning of the 16th century, the Castilians began exporting American cochineal (Dactylopius coccus) from Mexico, which was richer in colorant than the
European and Asian insects. The American dyestuff hence became a great success in European and Asian centres of textile production, and a lucrative commodity for the economy of the
Castilian Empire throughout the colonial period.
Using an interdisciplinary approach combining History and Chemistry, the current PhD project intends to take a closer look at the overall circulation of American cochineal as a commercial
product as well as its dynamics in the process of revolutionizing ancient dyeing practices among 16th- and 18th-century European and Asian textile workshops.
An ARCHLAB Transnational Access grant from the European Consortium CHARISMA project provided an invaluable opportunity to gain further knowledge about the contents of the archives of the Netherlands Cultural Heritage Agency, the National Gallery of London and the British Museum, and to have direct contact with their laboratory researchers. This experience facilitated access to reports and databases concerning cochineal insect dyes and their
analytical characterization in historical works of art, conducted by these institutions. Indeed, it wasfundamental for acknowledging the research made so far on cochineal dyes, as it allowed
a first evaluation of the types of historical textiles and possibly paintings that might be further studied in this PhD project. The information gathered also constituted an important
contribution for further developments of several sub-projects on the production, trade and circulation of 16th- and 17th-century historical textiles from Turkey, Iran, India and China in
the context of the Portuguese Overseas Expansion, currently being undertaken by art historians, museum curators, chemists and conservators under the auspices of the project TEXTILES, TRADE AND TASTE, PORTUGAL AND THE WORLD (TTT) at the Centre for Overseas History (CHAM) in Lisbon/Azores,to which this PhD project also belongs."
The history of natural red dyes involves power and extravagance. Difficult to acquire, luxurious ... more The history of natural red dyes involves power and extravagance. Difficult to acquire, luxurious red-dyed textiles were extremely valuable and only worn by a wealthy elite. The most dazzling red-dyes were obtained from cochineal insects. Collected in Central Europe and Central Asia, different species of Porphyrophora were extensively traded in medieval Europe and Asia. With the Iberian Expansion in the 16th century, the Spanish began exporting American cochineal (Dactylopius species) from Mexico, which achieved great success in Europe and Asia. Richer in colorant than other insects, this dyestuff brought enormous financial profit to the Spanish Empire [1-3].
The main aim of this paper is to understand the extent to which American cochineal was assimilated by European and Islamic textile production centres, in contrast to other, locally-available, red dye sources, such as kermes or Porphyrophora species. A small group of European and Islamic textiles originating from Italy, Turkey, Iran and India, and made between the 15th and 17th centuries, were analysed by High Performance Liquid Chromatography with Diode Array Detector (HPLC-DAD) and multivariate data analysis. A new methodology based on a mild extraction method, combined with a new dye recovery treatment, was applied to obtain HPLC chromatograms with good resolution. Hence, Principal Components Analysis (PCA) and Mass Spectrometry (MS) were used to identify the cochineal species present in the textiles, by comparing the results with a powerful PCA reference database, which consisted of diverse species of cochineal, collected from different regions in Europe, the Americas and Asia [4]. The methodology developed has successfully shown that it is possible to obtain accurate and consistent information for the identification of cochineal sources, in order to trace the assimilation process of American cochineal in European and Islamic dyeing traditions, beginning in the 16th century.
We are pleased to inform you that the deadline for the call for papers Dress under the Microscope... more We are pleased to inform you that the deadline for the call for papers Dress under the Microscope: Contributions of Science and Technology to the Study of Early Modern Dress is extended until 31 May. The Conference will be held at the National Museum of Theatre and Dance & National Museum of Costume in Lisbon, in cooperation with the TTT Network, CHAM - FCSH/NOVA on Thursday 12 and Friday 13 September 2019.
The scientific journal Conservar Património, in collaboration with the Textiles, Trade & Taste an... more The scientific journal Conservar Património, in collaboration with the Textiles, Trade & Taste and the University of Amsterdam, welcomes submissions for a special issue on the topic of historical textiles, and their investigation in the areas of conservation science, conservation and restoration, museum studies, archaeology, art history and other related disciplines.
In this tutorial, it is described step-by-step how to characterize chromatographic results of coc... more In this tutorial, it is described step-by-step how to characterize chromatographic results of cochineal dyes found in fibre samples from historical textiles, through models developed with partial-least squares discriminant analysis (PLS-DA). This tutorial has been developed in the framework of the doctoral project “The Red Road of the Iberian Expansion: Cochineal and the Global Dye Trade”.
Uploads
Papers by Ana Serrano
material composition changed in response to early modern colonialism and consumerism.
Scientific research was carried out with the aim to evaluate the response of modern and archaeological silks to temperature, relative humidity, light and oxygen, in order to define the most suitable parameters for the long-term storage and exhibition of the collection. Artificially aged samples taken from one of the archaeological fragments were analysed at the visual, structural and molecular level by means of colour measurements, Fourier transform infrared spectroscopy (FTIR) and ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FLD). The results showed that light exposure, in combination with high temperatures, oxygen and moisture strongly affected the silk's structure and molecular composition. Limiting exposure to light and removing oxygen reduced this effect and increased life expectancy significantly. Therefore, the analytical results obtained were essential to defining a preliminary preservation strategy for the collection: while on display, anoxic conditions slow down degradation of the silk by a factor of 4–5, whereas in a in dark storage, a low RH is the most important factor, with anoxic conditions providing additional reduction of decay.
Once in Europe, American dyes had a decisive impact on long-established dyeing traditions. Not only they allowed a wider range of colours, but they were also economically advantageous over European dyes. For instance, cochineal and indigo presented higher contents of colorant in relation to related local dyes, which allowed for larger numbers of cloth to be coloured. Hence, they were soon assimilated in the main European centres of textile production. However, in some regions, textile producers continued to prefer local dyes over the new ones.
An interdisciplinary investigation explored the diverse response of European territories to the trade and assimilation of American dyes in the textile centres, during the 16th and the 17th centuries. By combining historical research and chemical analyses of colorants in historical textiles, it was revealed that this process seems to have happened gradually, with more or less resistance, depending on the political and economic circumstances of each territory.
Noord-Holland, gegaan. In het najaar van 2015 is contact gezocht met de Universiteit van Amsterdam, conservering en restauratie van cultureel erfgoed (UvA-C&R) om mee te helpen met het beheer en behoud van het textiel.
Analytical investigation of the experimentally-dyed and artificially-aged fibres has demonstrated that the ratio of compounds in the insects dye composition can change, depending on the dyeing conditions applied and the type of fibres used. Similarities were observed when comparing the UHPLC-MS and SEM-EDX results from the dyed and aged references with the historical samples. This was verified with PLS-DA models of the chromatographic data, facilitating the classification of the cochineal species present in the historical samples. The majority of these samples were identified to contain American cochineal, which is in agreement with historical and dye identification literature that describe the impact of this dyestuff into European and Asian dyeing practices, after the Iberian Expansion in the 16th century.
The analytical results emphasize the importance of using statistical data interpretation for the discrimination of cochineal dyes, besides qualitative and quantitative evaluation of chromatograms. Hence, the combination of UHPLC-PDA with a statistical classification method, such as PLS-DA, has been demonstrated to be an advisable approach in future investigations to assess closely related species of natural dyes in historical textile samples. This is particularly important when aiming to achieve more accurate interpretations about the history of works of art, or the application of natural dyes in old textile production.
In the framework of the project “THE RED ROAD OF THE IBERIAN EXPANSION: Cochineal and the Global Dye Trade”, the colours of historical textiles belonging to the Catharijnconvent museum collection were studied to assess the use of local and faraway- imported sources of colour, especially cochineal, into the European dyeing industry, in the transition between the Middle Ages and the beginning of the Age of Discoveries.
liquid chromatography with a diode array detector (HPLC-DAD) and submitted to multivariate data analysis, in order to discriminate the species and hence construct a reference library for a wide range of applications. Principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA)
models successfully provided accurate species classifications. This library was then applied to the identification of 72 historical insect specimens of unidentified species, mostly dating from the 19th
century, and belonging to the Economic Botany Collection, Royal Botanic Gardens, Kew, England. With this approach it was possible to identify anomalies in how insects were labelled historically, as several of them were revealed not to be cochineal. Nevertheless, more than 85% of the collection was determined to be species of Dactylopius and the majority of the specimens were identified as D. coccus. These results have shown that HPLC-DAD, in combination with suitable chemometric methods, is a powerful
approach for discriminating related cochineal species.
TASTE, PORTUGAL AND THE WORLD (TTT), under development at the CHAM, FCSHUNL & UAç. The main aim of this project is the interdisciplinary study of historical textiles, by involving the work of a dozen of researchers from History, Chemistry and Conservation areas in Portugal. It currently comprises several sub-projects, which are especially focused on the historical and chemical study of ancient textiles, dating from 16th and 17th centuries.
The contact between TTT and CHARISMA projects was recently accomplished through the ARCHLAB Transnational Access, representing an important contribution for the development of Ana Serrano‘s PhD thesis, ―The Red Road of the Iberian Expansion:
Cochineal and the global dye trade‖. The invaluable visit to the Netherlands Cultural Heritage Agency (RCE), the National Gallery of London (NGL) and the British Museum (BM) allowed the exclusive contact with reports and databases concerning cochineal insect dyes and their analytical characterization in historical works of art, which is accomplished by specialized researchers at the advanced facilities from these institutions. This ARCHLAB Transnational Access grant revealed to be fundamental to acknowledge the research made on cochineal dyes until now, as it permitted a more definitive construction of the phases of this sub-project, which is described in detail below."
Theses by Ana Serrano
The historical investigation comprised a comprehensive revision of historical publications and primary printed sources regarding the Iberian transatlantic trade in dyestuffs and their impact on European and Asian dyeing traditions during the Early Modern period. Special focus was given to the acceptance of American cochineal over local insect dye sources, namely kermes, lac and Armenian and Polish cochineal. This research reveals a gradual but clear adoption of the American dyestuff in Europe and in West Asia, although local insect dyes would still have a representative role in on-going practices, especially in East and Southeast Asia.
Chemical research was pursued to evaluate the historical picture presented for the impact of the American dyestuff in Europe and, especially in Asia, to which insufficient historical information was available. Given that previous publications concerning the chemical characterization of insect dyes depicted limitations that compromised the differentiation of cochineal species in red-dyed historical textiles, an ultra high-performance liquid chromatography (UHPLC) method was optimized to deliver more accurate results. Then, experiments with cochineal and kermes dyes were undertaken following several dyeing parameters. The resulting dyed fibres were characterized with UHPLC, leading to meaningful insights about the behaviour of the colorants’ dye compounds. Subsequent artificial ageing of the dyed fibres and their characterization with mass spectrometry (MS) permitted to characterize, for the first time, photo-degradation compounds in the insect’s colorant. These results were reported to be similar to those for historical fibres and, for this reason, it became possible to compare the experimentally-dyed and historical fibres through partial-least squares discriminant analysis (PLS-DA), for the identification of the cochineal species used to colour the analysed historical fibres.
By combining the results of this successful approach, along with the results for other coloured historical fibres and their contextualization with historical evidence, it was possible to ascribe assertive interpretations about the date and provenance of the investigated textiles. Moreover, successful historical interpretations could be obtained about the dynamics of American cochineal in European and Asian societies throughout the colonial period. Therefore, the interdisciplinary combination of chemical and statistical methods developed here, along with historical evidence, has proven to be an important approach that should be adopted in future projects for the characterization of insect dyes in cultural heritage objects.
Therefore, a new approach on the study of cochineal species present in historical textiles was developed. Different parameters for the analysis conditions were undertaken to optimize the results for both insect species and textiles samples. Afterwards, with Principal Components Analysis (PCA), results from textiles samples exhibited a satisfactory correlation when compared with a cochineal reference database. Moreover, High-performance Liquid Chromatography with Diode Array Detector coupled with Mass Spectrometry (HPLC/DAD/MSn) analysis could offer accurate information on cochineal species and textiles samples. The characterization of six species of cochineal allowed, through PCA and HPLC/DAD/MSn analysis, the identification of unidentified cochineal insect samples and a group of Islamic and Italian historical dyed-cochineal textiles, dated from 15th to 17th centuries.
This identification contributes to connect the textiles’ history, and the trade and dyeing technologies on possible different species of cochineal. This fact regards especially textiles produced in the main textile centres, where, after the 16th century, the traded American cochineal was swiftly adopted, as many historical publications assert. Although this study identified American cochineal in a 17th-century Indian textile for the first time, the results for the other analyzed textiles did not reveal the presence of this species. In this way, the possibility of the prompt spread of the American specie in European and Asian textiles dyeing seems to be more complex than what is emphasized by present publications."
Conference Posters by Ana Serrano
To assess the quality and historical background of these textiles, as well as their state of conservation for future preservation strategies, their materials have been characterized. A total of 218 textile yarns and metal threads were sampled from 34 fragments to 1) characterize the dyestuffs and mordants used, 2) to identify and evaluate the condition of the textile fibres, and 3) to assess the composition and condition of the metal threads.
With ultra-high performance liquid chromatography coupled to diode array detector (UHPLC-PDA), it was verified that most fragments were coloured with insect dyes, and in some cases, madder and tannins as well. With research microscopy and scanning electron microscopy - energy dispersive x-ray spectrometer (SEM-EDX), silk fibres were mostly identified and these appeared clean, smooth and flexible; although those from more fragile fragments were evidently more friable and dirty, presenting pitting from biodegradation and contaminations from the archaeological environment. Silver sulphide crystals from the corrosion of silver were mostly observed on the metal threads, and gold was often detected, indicating that these were gilded. Even though the historical background of these fragments is still under investigation, it is undoubtedly clear that this is quite a lavish, unique finding that deserves to be fully appreciated and preserved for generations to come.
material composition changed in response to early modern colonialism and consumerism.
Scientific research was carried out with the aim to evaluate the response of modern and archaeological silks to temperature, relative humidity, light and oxygen, in order to define the most suitable parameters for the long-term storage and exhibition of the collection. Artificially aged samples taken from one of the archaeological fragments were analysed at the visual, structural and molecular level by means of colour measurements, Fourier transform infrared spectroscopy (FTIR) and ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FLD). The results showed that light exposure, in combination with high temperatures, oxygen and moisture strongly affected the silk's structure and molecular composition. Limiting exposure to light and removing oxygen reduced this effect and increased life expectancy significantly. Therefore, the analytical results obtained were essential to defining a preliminary preservation strategy for the collection: while on display, anoxic conditions slow down degradation of the silk by a factor of 4–5, whereas in a in dark storage, a low RH is the most important factor, with anoxic conditions providing additional reduction of decay.
Once in Europe, American dyes had a decisive impact on long-established dyeing traditions. Not only they allowed a wider range of colours, but they were also economically advantageous over European dyes. For instance, cochineal and indigo presented higher contents of colorant in relation to related local dyes, which allowed for larger numbers of cloth to be coloured. Hence, they were soon assimilated in the main European centres of textile production. However, in some regions, textile producers continued to prefer local dyes over the new ones.
An interdisciplinary investigation explored the diverse response of European territories to the trade and assimilation of American dyes in the textile centres, during the 16th and the 17th centuries. By combining historical research and chemical analyses of colorants in historical textiles, it was revealed that this process seems to have happened gradually, with more or less resistance, depending on the political and economic circumstances of each territory.
Noord-Holland, gegaan. In het najaar van 2015 is contact gezocht met de Universiteit van Amsterdam, conservering en restauratie van cultureel erfgoed (UvA-C&R) om mee te helpen met het beheer en behoud van het textiel.
Analytical investigation of the experimentally-dyed and artificially-aged fibres has demonstrated that the ratio of compounds in the insects dye composition can change, depending on the dyeing conditions applied and the type of fibres used. Similarities were observed when comparing the UHPLC-MS and SEM-EDX results from the dyed and aged references with the historical samples. This was verified with PLS-DA models of the chromatographic data, facilitating the classification of the cochineal species present in the historical samples. The majority of these samples were identified to contain American cochineal, which is in agreement with historical and dye identification literature that describe the impact of this dyestuff into European and Asian dyeing practices, after the Iberian Expansion in the 16th century.
The analytical results emphasize the importance of using statistical data interpretation for the discrimination of cochineal dyes, besides qualitative and quantitative evaluation of chromatograms. Hence, the combination of UHPLC-PDA with a statistical classification method, such as PLS-DA, has been demonstrated to be an advisable approach in future investigations to assess closely related species of natural dyes in historical textile samples. This is particularly important when aiming to achieve more accurate interpretations about the history of works of art, or the application of natural dyes in old textile production.
In the framework of the project “THE RED ROAD OF THE IBERIAN EXPANSION: Cochineal and the Global Dye Trade”, the colours of historical textiles belonging to the Catharijnconvent museum collection were studied to assess the use of local and faraway- imported sources of colour, especially cochineal, into the European dyeing industry, in the transition between the Middle Ages and the beginning of the Age of Discoveries.
liquid chromatography with a diode array detector (HPLC-DAD) and submitted to multivariate data analysis, in order to discriminate the species and hence construct a reference library for a wide range of applications. Principal components analysis (PCA) and partial least squares discriminant analysis (PLSDA)
models successfully provided accurate species classifications. This library was then applied to the identification of 72 historical insect specimens of unidentified species, mostly dating from the 19th
century, and belonging to the Economic Botany Collection, Royal Botanic Gardens, Kew, England. With this approach it was possible to identify anomalies in how insects were labelled historically, as several of them were revealed not to be cochineal. Nevertheless, more than 85% of the collection was determined to be species of Dactylopius and the majority of the specimens were identified as D. coccus. These results have shown that HPLC-DAD, in combination with suitable chemometric methods, is a powerful
approach for discriminating related cochineal species.
TASTE, PORTUGAL AND THE WORLD (TTT), under development at the CHAM, FCSHUNL & UAç. The main aim of this project is the interdisciplinary study of historical textiles, by involving the work of a dozen of researchers from History, Chemistry and Conservation areas in Portugal. It currently comprises several sub-projects, which are especially focused on the historical and chemical study of ancient textiles, dating from 16th and 17th centuries.
The contact between TTT and CHARISMA projects was recently accomplished through the ARCHLAB Transnational Access, representing an important contribution for the development of Ana Serrano‘s PhD thesis, ―The Red Road of the Iberian Expansion:
Cochineal and the global dye trade‖. The invaluable visit to the Netherlands Cultural Heritage Agency (RCE), the National Gallery of London (NGL) and the British Museum (BM) allowed the exclusive contact with reports and databases concerning cochineal insect dyes and their analytical characterization in historical works of art, which is accomplished by specialized researchers at the advanced facilities from these institutions. This ARCHLAB Transnational Access grant revealed to be fundamental to acknowledge the research made on cochineal dyes until now, as it permitted a more definitive construction of the phases of this sub-project, which is described in detail below."
The historical investigation comprised a comprehensive revision of historical publications and primary printed sources regarding the Iberian transatlantic trade in dyestuffs and their impact on European and Asian dyeing traditions during the Early Modern period. Special focus was given to the acceptance of American cochineal over local insect dye sources, namely kermes, lac and Armenian and Polish cochineal. This research reveals a gradual but clear adoption of the American dyestuff in Europe and in West Asia, although local insect dyes would still have a representative role in on-going practices, especially in East and Southeast Asia.
Chemical research was pursued to evaluate the historical picture presented for the impact of the American dyestuff in Europe and, especially in Asia, to which insufficient historical information was available. Given that previous publications concerning the chemical characterization of insect dyes depicted limitations that compromised the differentiation of cochineal species in red-dyed historical textiles, an ultra high-performance liquid chromatography (UHPLC) method was optimized to deliver more accurate results. Then, experiments with cochineal and kermes dyes were undertaken following several dyeing parameters. The resulting dyed fibres were characterized with UHPLC, leading to meaningful insights about the behaviour of the colorants’ dye compounds. Subsequent artificial ageing of the dyed fibres and their characterization with mass spectrometry (MS) permitted to characterize, for the first time, photo-degradation compounds in the insect’s colorant. These results were reported to be similar to those for historical fibres and, for this reason, it became possible to compare the experimentally-dyed and historical fibres through partial-least squares discriminant analysis (PLS-DA), for the identification of the cochineal species used to colour the analysed historical fibres.
By combining the results of this successful approach, along with the results for other coloured historical fibres and their contextualization with historical evidence, it was possible to ascribe assertive interpretations about the date and provenance of the investigated textiles. Moreover, successful historical interpretations could be obtained about the dynamics of American cochineal in European and Asian societies throughout the colonial period. Therefore, the interdisciplinary combination of chemical and statistical methods developed here, along with historical evidence, has proven to be an important approach that should be adopted in future projects for the characterization of insect dyes in cultural heritage objects.
Therefore, a new approach on the study of cochineal species present in historical textiles was developed. Different parameters for the analysis conditions were undertaken to optimize the results for both insect species and textiles samples. Afterwards, with Principal Components Analysis (PCA), results from textiles samples exhibited a satisfactory correlation when compared with a cochineal reference database. Moreover, High-performance Liquid Chromatography with Diode Array Detector coupled with Mass Spectrometry (HPLC/DAD/MSn) analysis could offer accurate information on cochineal species and textiles samples. The characterization of six species of cochineal allowed, through PCA and HPLC/DAD/MSn analysis, the identification of unidentified cochineal insect samples and a group of Islamic and Italian historical dyed-cochineal textiles, dated from 15th to 17th centuries.
This identification contributes to connect the textiles’ history, and the trade and dyeing technologies on possible different species of cochineal. This fact regards especially textiles produced in the main textile centres, where, after the 16th century, the traded American cochineal was swiftly adopted, as many historical publications assert. Although this study identified American cochineal in a 17th-century Indian textile for the first time, the results for the other analyzed textiles did not reveal the presence of this species. In this way, the possibility of the prompt spread of the American specie in European and Asian textiles dyeing seems to be more complex than what is emphasized by present publications."
To assess the quality and historical background of these textiles, as well as their state of conservation for future preservation strategies, their materials have been characterized. A total of 218 textile yarns and metal threads were sampled from 34 fragments to 1) characterize the dyestuffs and mordants used, 2) to identify and evaluate the condition of the textile fibres, and 3) to assess the composition and condition of the metal threads.
With ultra-high performance liquid chromatography coupled to diode array detector (UHPLC-PDA), it was verified that most fragments were coloured with insect dyes, and in some cases, madder and tannins as well. With research microscopy and scanning electron microscopy - energy dispersive x-ray spectrometer (SEM-EDX), silk fibres were mostly identified and these appeared clean, smooth and flexible; although those from more fragile fragments were evidently more friable and dirty, presenting pitting from biodegradation and contaminations from the archaeological environment. Silver sulphide crystals from the corrosion of silver were mostly observed on the metal threads, and gold was often detected, indicating that these were gilded. Even though the historical background of these fragments is still under investigation, it is undoubtedly clear that this is quite a lavish, unique finding that deserves to be fully appreciated and preserved for generations to come.
It has been previously shown that High-Performance Liquid Chromatography (HPLC), along with components quantification, cannot provide a precise characterization of the cochineal insect species, and for this reason, multivariate statistical analyses are needed to compare the resulting chromatograms [1]. As good resolution chromatograms are required to ensure the correct discrimination of the components present in cochineal species, it was opted to undertake an optimization of the analysis conditions using Ultra high-Performance Liquid Chromatography (UPLC). This very recent technique presents several advantages over HPLC, as it can provide a better resolution, owing to the smaller particle size columns [2], essential for the low molecular weight from dyestuff components. Therefore, the optimization of the analytical conditions comprised three main parameters: several UPLC columns of different dimensions and stationary phase composition; different elution gradients, adapted from previously published HPLC methods used for dyestuffs characterization [3]; and mixtures of natural dyestuffs extracts, which included the main components commonly found in historical textiles. The optimized elution method for UPLC was then applied to a HPLC column, hence demonstrating that UPLC analyses provide more accurate results than HPLC. Indeed, the Limit of Detection (LOD) significantly improved with UPLC, which allowed the acquisition of more precise data, extremely valuable for the characterization of minor components present in dyestuffs. Therefore, this research is of upmost importance, as it represents the first application of UPLC analyses into the field of dyestuff analysis related to cultural heritage.
[1] Serrano, Ana, Sousa, Micaela M., Hallett, Jessica, Lopes, João A., Oliveira, M. Conceição, “Analysis of natural red dyes (cochineal) in textiles of historical importance using HPLC and multivariate data analysis”, Analytical and Bioanalytical Chemistry, 401 (2011) 735-743.
[2] Guillarme, D., Ruta, J., Rudaz, S., Veuthey, J., “New trends in fast and high-resolution liquid chromatography : a critical comparison of existing approaches”, Analytical and Bioanalytical Chemistry, 397 (2010) 1069-1082.
[3] Joosten, Ineke, van Bommel, Maarten, “Critical evaluation of micro-chemical analysis of archaeological materials”, Microchimica Acta, 162 (2008), 433-466.
The interdisciplinary CarpetACT project combines art history with analytical and data sciences, with the aim to improve the weaving examination of these complex carpets, by considering the spin of threads; the ply and twist of yarns; the thread count and density; and the weaving structure of warps, wefts and piles. Several non-invasive analytical techniques, namely video spectral comparator (VSC), X-radiography, tomography and (micro) CT scanning are tested to assess a small group of 16th- and 17th-century Islamic knotted-pile carpets or fragments of these objects, belonging to the Rijksmuseum collection. Machine-learning methods are developed to process and compare digital photographs from these objects and a large quantity of data obtained with the tested analytical techniques. Ultimately, the outcome of this approach is compared with the results obtained with the traditional technical examination based on visual observations of the carpets.
Within this feasibility study, it has been possible to highlight the possibilities and limitations of the tested imaging techniques, and the potential of data science to enhance the interpretation process of their results. Indeed, this approach has enabled to identify technological details about the carpets’ weaving structure, as well as about their present condition and past restorations that passed unnoticed with the traditional technical examination. Therefore, the outcome of this research brings unprecedented contributions to art historical and conservation research and, in particular, to the future of the technological study of historical textiles.
Eens in Europa, hadden deze kleurstoffen een beslissende invloed op oude verftradities. Niet alleen creërden ze een breder assortiment aan kleuren, maar ook waren ze economisch voordeliger dan de Europese kleurstoffen. Zo bevatten cochenille en indigo een hoger gehalte aan kleurstof in vergelijking met verwante lokale kleurstoffen en hierdoor kon er meer kleren geverft worden met dezelfde hoeveelheid. Desalniettemin, vervolgden de stoffenververs het gebruik van traditionele kleurstoffen in bepaalde regio´s.
Een interdisciplinair onderzoek is uitgevoerd naar de Europese reactie en assimilatie van de Amerikaanse kleurstoffen in 16e en 17e eeuwse textielcentra. Historisch onderzoek en chemische analyses van kleur in historische textielen hebben aangetoond dat dit proces langzaam op gang kwam met enige weerstand, afhankelijk van politieke en economische omstandigheden van elk gebied.
To understand the origin and function of these textiles, as well as their state of conservation for future preservation strategies, it was important to characterize their materials. Hence, a group of 12 objects was selected for evaluation with ultra-high performance liquid chromatography with diode array detector (UHPLC-PDA) and a scanning electron microscope coupled to an energy dispersive x-ray spectrometer (SEM-EDX).
With UHPLC-PDA, coccid insect dyes were identified as the main colorants on the textiles. However, the ratio of their dye compounds seems to have been affected by the maritime archaeological conditions: dcII and flavokermesic acid were not reported in any of the textiles; and an unusually high kermesic acid equivalent was detected, in relation to the major compounds kermesic and carminic acids. Even though American cochineal and kermes could be possibly attributed in some cases, these results substantially hinder the precise identification of the insect sources. Besides these, madder was often found mixed with the insect dyes or in textile parts that are not directly visible on the costumes.
The evaluation of the fibres with SEM-EDX indicated that some fibres show evidence of microorganism attack, and that the majority has preserved their flexibility; although those from fabrics of lower quality (e.g. lining) are more friable. On the metal threads, silver sulphide crystals were observed, and these correspond to the degradation product of silver. Also, gold was detected on few threads, which indicates that they were probably gilded. Due to the corrosion of silver, most gold particles could have been lost in the maritime environment.
While the provenance of these textiles, and the ship that carried them, is still under investigation, the analytical results obtained undoubtedly prove that a very rich finding has been unearthed. Nevertheless, the archaeological conditions certainly had a preponderant influence on their original appearance and this deserves future research.
Given the similar colorant composition of these red dye sources, a characterization study was performed on textile samples to assess possible modifications that can lead to a more accurate knowledge of their presence in historical textiles. Based on the work performed by Golikov [1,2], as well as other contemporary studies and historical recipes dated between the 15th and 18th centuries, several parameters for dyeing crimson were tested on silk and wool with American cochineal. Therefore, the influence of the pH, temperature, duration and the addition of ingredients such as soap, cream of tartar or turmeric were assessed. Then, the parameters that suited the best shades of crimson were selected to dye with kermes, Armerian and Polish cochineal.
Subsequently, the dyed samples were analyzed with ultrahigh pressure liquid chromatography coupled to a photodiode array detector (UHPLC-PDA) [3] and the chromatograms were analysed qualitatively and quantitatively with multivariate statistical data analysis methods [4]. The methodology developed demonstrated that it is possible to obtain consistent information about dyed samples and their composition, according to the experimental parameters and the textile substrate used. Along with the revision of historical sources for dyeing, this study has brought invaluable contributions to the study of cochineal and kermes insect sources used to dye historical textile samples, as well as to the historical evaluation of the incorporation of American cochineal into European and Asian dyeing traditions, from the 16th century onwards.
knowledge. Until the end of the 15th century, different species of Porphyrophora cochineal insects were collected and extensively traded throughout Europe and Asia. However, with the
Iberian Expansion at the beginning of the 16th century, the Castilians began exporting American cochineal (Dactylopius coccus) from Mexico, which was richer in colorant than the
European and Asian insects. The American dyestuff hence became a great success in European and Asian centres of textile production, and a lucrative commodity for the economy of the
Castilian Empire throughout the colonial period.
Using an interdisciplinary approach combining History and Chemistry, the current PhD project intends to take a closer look at the overall circulation of American cochineal as a commercial
product as well as its dynamics in the process of revolutionizing ancient dyeing practices among 16th- and 18th-century European and Asian textile workshops.
An ARCHLAB Transnational Access grant from the European Consortium CHARISMA project provided an invaluable opportunity to gain further knowledge about the contents of the archives of the Netherlands Cultural Heritage Agency, the National Gallery of London and the British Museum, and to have direct contact with their laboratory researchers. This experience facilitated access to reports and databases concerning cochineal insect dyes and their
analytical characterization in historical works of art, conducted by these institutions. Indeed, it wasfundamental for acknowledging the research made so far on cochineal dyes, as it allowed
a first evaluation of the types of historical textiles and possibly paintings that might be further studied in this PhD project. The information gathered also constituted an important
contribution for further developments of several sub-projects on the production, trade and circulation of 16th- and 17th-century historical textiles from Turkey, Iran, India and China in
the context of the Portuguese Overseas Expansion, currently being undertaken by art historians, museum curators, chemists and conservators under the auspices of the project TEXTILES, TRADE AND TASTE, PORTUGAL AND THE WORLD (TTT) at the Centre for Overseas History (CHAM) in Lisbon/Azores,to which this PhD project also belongs."
The main aim of this paper is to understand the extent to which American cochineal was assimilated by European and Islamic textile production centres, in contrast to other, locally-available, red dye sources, such as kermes or Porphyrophora species. A small group of European and Islamic textiles originating from Italy, Turkey, Iran and India, and made between the 15th and 17th centuries, were analysed by High Performance Liquid Chromatography with Diode Array Detector (HPLC-DAD) and multivariate data analysis. A new methodology based on a mild extraction method, combined with a new dye recovery treatment, was applied to obtain HPLC chromatograms with good resolution. Hence, Principal Components Analysis (PCA) and Mass Spectrometry (MS) were used to identify the cochineal species present in the textiles, by comparing the results with a powerful PCA reference database, which consisted of diverse species of cochineal, collected from different regions in Europe, the Americas and Asia [4]. The methodology developed has successfully shown that it is possible to obtain accurate and consistent information for the identification of cochineal sources, in order to trace the assimilation process of American cochineal in European and Islamic dyeing traditions, beginning in the 16th century.
More information at http://www.dressingtheearlymodern.com/Conferences.html
You may find this tutorial, along with PLS-DA models, at https://github.com/CochinealDyes/PLS-DA-models.