Ammonium carbonate was used as the carbonation accelerator for air-hardening lime mortars in this... more Ammonium carbonate was used as the carbonation accelerator for air-hardening lime mortars in this study. Various analytical methods, including XRD, IR, TGA-DSC and SEM were employed to access the phase transformation, degree of carbonation and microstructural features of the lime-based mortars. The paper explores the correlation between the mechanical strength, microstructure of cured lime mortars and the composition/ carbonation degree with the crystallization behaviors in Ca(OH)2/CaCO3 binders. The results indicate that ammonium carbonate significantly accelerates the carbonation reaction and increases the early mechanical strength of air-hardening lime mortars. The mechanical strength of these modified lime mortars can be comparable to that of natural hydraulic lime (NHL). The aggregation behaviors of nano-CaCO3 under kinetic control, are believed to contribute much to the compact pore-structures and robust mechanical strength of lime mortars. This viable accelerating carbonation method holds promise for enhancing the properties of various limecontaining building materials in conservation and modern buildings.
Restoring ancient civilizations through cultural heritage conservation science Cultural heritage ... more Restoring ancient civilizations through cultural heritage conservation science Cultural heritage embodies the collective memory and identity of civilizations that have spanned centuries and continents. Understanding and preserving cultural heritage is of utmost importance as it provides invaluable insights into our past and serves as a bridge to the future. Cultural heritage conservation science employs a multidisciplinary approach that combines scientific research, technological advancements, and conservation ethics. It brings together experts from diverse academic fields such as materials science, chemistry, biology, civil engineering, geological sciences, architecture, archaeology, and history. By harnessing their knowledge and expertise, these professionals strive to restore ancient civilizations concealed within cultural artifacts and tackle the intricate challenges associated with safeguarding our cultural heritage. Fundamental aspects of cultural heritage conservation science encompass the study of cultural heritage materials, the development of conservation materials, and the implementation of conservation methodologies. The study of cultural heritage materials allows us to comprehend ancient civilizations and provides support for the application of materials and methods in cultural heritage conservation. Conservation materials are designed to aid ancient materials in retaining some of their original properties and mitigate further deterioration. The development and implementation of conservation methodologies aim to ensure the preservation, understanding, and appreciation of cultural heritage for both the present and the future. We are delighted to present this special topic of Science China Technological Sciences, dedicated to the captivating realm of cultural heritage conservation science. The objective of this issue is to shed light on the latest advancements and breakthroughs in this field. The topics covered encompass a broad array of themes, ranging from the development of new materials for conservation purposes to the application of innovative characterization techniques for analyzing cultural heritage materials. Moreover, the issue delves into the development and implementation of novel conservation methodologies, as well as the understanding of degradation phenomena in cultural heritage materials and sites. The materials addressed in this issue include earthen sites, bronzes, ceramic glazes, textiles, lacquerware, as well as the development of consolidants for stones and papers, and cleaning materials for paintings. Such comprehensive coverage reflects the extensive breadth and diversity of research in cultural heritage conservation science. Each contribution offers unique insights into the challenges faced by different cultural contexts, thereby providing a mosaic of knowledge that propels the field of cultural heritage conservation science forward. We invite you to embark on a captivating journey through the realm of cultural heritage conservation science, as illuminated by the articles in this special issue. Our hope is that this collection inspires scientists, conservation professionals, archaeologists, policymakers, and the wider public to recognize the value and urgency of cultural heritage conservation, as well as the significance of science and technology in restoring ancient civilizations. May this compilation ignite curiosity, spark meaningful conversations, and drive future research endeavors aimed at safeguarding our heritage for generations to come. We express our heartfelt gratitude to all the authors, reviewers, and editorial staff who have contributed their expertise, time, and unwavering dedication to shaping this special issue. Their collaborative spirit and commitment to excellence have ensured the high caliber of the research presented herein.
Cultural relics are man-made objects left from ancient times, with historical, artistic and scien... more Cultural relics are man-made objects left from ancient times, with historical, artistic and scientific values. Multi-interdisciplinary research of cultural relics would enable people to obtain a variety of information, from which the restoration of ancient civilization is possible. Due to natural weathering, many cultural relics are in a fragile state, and conservation treatments that can prolong their lifetime are important, which may involve the use of conservation materials. In this paper, we define the new term “Herit-Materials” as two type of materials, including ancient cultural relics themselves and novel functional materials for conservation purposes. For the first type of Herit-Materials- cultural relics themselves, as one type of ancient materials, the concept on the relationship between the structure, composition, performance and technology of them has been introduced, along with the research paradigm for ancient cultural relics. Following such a paradigm, the way how analysis and research has been performed on ancient cultural relics are illustrated in detail with examples of ancient ceramics and textile dyes. Meanwhile, as the second type of Herit-Materials, three categories of conservation materials, such as emergent conservation materials on archaeological sites, consolidation materials and cleaning materials have been reviewed in detail, including basic concepts, criteria for choosing appropriate materials for conservation purposes, evaluation of the conservation effects after application, along with the application methods of those conservation materials. Finally, as Herit-Materials’ studies have attracted many researchers and have also created new inter-disciplinary research fields, the following research directions are recommended for scholars who have interest, including the development of advanced and comprehensive analytical technique of Herit-Materials, non-destructive and in-situ characterization & testing of Herit-Materials, the database of composition-structure-performance for Herit-Materials and their real-time environmental conditions, the green Herit-Materials for conservation purposes and their application methods, as well as the type and pattern analysis research of Herit-Materials.
Lime mortars have taken an important role in constructing ancient Chinese masonry structures, inc... more Lime mortars have taken an important role in constructing ancient Chinese masonry structures, including city walls, buildings, and tombs. A tomb built with lime mortars and stones belonging a Ming high-rank official Xu Jie was discovered in Huzhou City of China. Eight different samples from Xu Jie’s tomb, representing four types of lime-mortar based materials: joint mortar between stone bricks, bedding mortar, grouting mortar, and plaster mortars were collected for analysis and comparison. The characterization of the construction materials has therefore become of primary importance. The function of each mortar was reported and studies into the micro-textural features and mineralogical compositions of those mortars were performed via a multi-analytical approach. The joint mortars were all found to be aerial lime mortars with predominately lime. The bedding mortar was found to consist of lime, soil and sand, typical of a tabia mortar. The grouting mortar was found to consist of lime and ground contact metamorphosed limestone. Analysis of plaster sample taken from the roof of the main tomb identified the presence of calcium stearate/palmitate, indicating the usage of plant-based Tung oil as an additive. The analytical results will promote our understanding of Ming architectural technology and craftsmanship, and provide critical information for the conservation of Xu Jie’s tomb.
This research investigates and evaluates the optical, physical, and chemical interactions between... more This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into cal...
ABSTRACT This research develops hydroxyapatite (HAP)-based, inorganic mineral systems for the con... more ABSTRACT This research develops hydroxyapatite (HAP)-based, inorganic mineral systems for the consolidation of powdery wall paintings of archaeological significance. The scientific approach exploits biomimetic (biologically inspired design) principles to induce in situ the formation of protective HAP crystals by triggering reactions between the calcium carbonate-rich layers in wall paintings and ammonium phosphate precursors. The high solubility and absence of toxicity of ammonium phosphate precursors and the stability of the hydroxyapatite reaction product at varying pH, renders this treatment extremely promising for consolidation and protection of weathered wall paintings. Experimental trials were carried out on wall painting test blocks applying cellulose compresses of 1M and 2M solutions of diammonium hydrogen phosphate for 3 to 6 hours contact time. The consolidating effect was evaluated through microstructurally and compositionally-sensitive analytics including VPSEM-EDS, XRF, water sorption test and scotch tape test. Preliminary results indicated the formation of a porous hydroxyapatite network at the surface and subsurface of the test blocks with improved cohesion, pH-resistivity and reduced water absorption. These data show the potential of this treatment for the consolidation of powdery wall paintings and their protection from weathering and deterioration induced by natural aging and environmental action-linked effects.
Formation and aggregation of metal carboxylates (metal soaps) can degrade the appearance and inte... more Formation and aggregation of metal carboxylates (metal soaps) can degrade the appearance and integrity of oil paints, challenging efforts to conserve painted works of art. Endeavors to understand the root cause of metal soap formation have been hampered by the limited spatial resolution of Fourier transform infrared microscopy (μ-FTIR). We overcome this limitation using optical photothermal infrared spectroscopy (O-PTIR) and photothermal-induced resonance (PTIR), two novel methods that provide IR spectra with ≈500 and ≈10 nm spatial resolutions, respectively. The distribution of chemical phases in thin sections from the top layer of a 19th-century painting is investigated at multiple scales (μ-FTIR ≈ 10 2 μm 3 , O-PTIR ≈ 10 −1 μm 3 , PTIR ≈ 10 −5 μm 3). The paint samples analyzed here are found to be mixtures of pigments (cobalt green, lead white), cured oil, and a rich array of intermixed, small (often ≪ 0.1 μm 3) zinc soap domains. We identify Zn stearate and Zn oleate crystalline soaps with characteristic narrow IR peaks (≈1530−1558 cm −1) and a heterogeneous, disordered, water-permeable, tetrahedral zinc soap phase, with a characteristic broad peak centered at ≈1596 cm −1. We show that the high signal-to-noise ratio and spatial resolution afforded by O-PTIR are ideal for identifying phase-separated (or locally concentrated) species with low average concentration, while PTIR provides an unprecedented nanoscale view of distributions and associations of species in paint. This newly accessible nanocompositional information will advance our knowledge of chemical processes in oil paint and will stimulate new art conservation practices.
The characterization of lime mortars has become of primary importance in order to obtain informat... more The characterization of lime mortars has become of primary importance in order to obtain information about the raw ingredients and building technology of ancient masonry structures. Five different samples from Anhui province, China, representing two types of lime mortar‐based materials: joint mortars between the bricks of the city wall and lime mortar sealing a tomb coffin, were collected for analysis. Archaeological information about the samples was reported and studies into the microtextural features and mineralogical compositions of those mortars were performed via a multi‐analytical approach. The joint lime mortars between the bricks of city walls, including Mingzhongdu city wall, Mingzhongdu Xihua gate foundation, Zhengyangguan city wall and She county city wall, were found to be aerial lime mortars. The lime mortar from Nanling Tieguai Song dynasty tomb was analysed and found to be a pozzolanic mortar consisting of lime, clay, sand and cocciopesto‐like materials. The analytical results serve as a critical reference for the maintenance and restoration of ancient city walls in Anhui province, and as a starting point for searching for ancient Chinese pozzolanic mortars and technology for making those mortars.
A theoretical and experimental approach was applied to investigate phase relations in a system co... more A theoretical and experimental approach was applied to investigate phase relations in a system containing calcium carbonate and different ammonium phosphate solutions. Using laboratory experiments and thermodynamic modeling, this paper provides an insight into the formation of stable phase assemblages in the calcium carbonate and mono‐, di‐, triammonium phosphate aqueous system. Focus is placed on the morphological and mineralogical characterization and thermodynamic calculation of calcium phosphates precipitating due to the reaction between the calcium carbonate and ammonium phosphate solutions. Correlations between the formed stable calcium phosphate phases and the ammonium phosphate precursors are provided. Advantages and limitations of various analytical and modeling techniques used in this study such as geochemical equilibrium‐based modeling, X‐ray diffraction, scanning electron microscopy, and thermal analysis, are critically evaluated. Additionally, possible impacts of the ammonium phosphate solution type on the kinetics of phase transformations are discussed.
Materials in the paint layers of an early sixteenth-century painted and glazed terracotta sculptu... more Materials in the paint layers of an early sixteenth-century painted and glazed terracotta sculpture by Giovanni della Robbia, Pietà were identified. The presence of the rare lead chloride salts, cotunnite (PbCl2) and challacolloite (KPb2Cl5), were confirmed using Raman spectroscopy and electron back scatter diffraction. Well-formed habit of large crystals of challacolloite indicates slow growth from solution. The stability and potential pathways for the in-situ formation of lead chloride compounds are discussed. The presence of lead chloride phases in the Pietà indicates conditions of high chloride ion concentrations (i.e., activities) and/or low pH led to the alteration of the pigment lead white (hydrocerussite, 2PbCO3·Pb(OH)2). This work highlights the role of ion transport in alteration of artists’ materials and emphasizes the importance of considering the role of treatments and envi-ronmental factors in changes in materials, and reinforces our awareness of the on-going chemistry occurring in works of art.
Oil paints comprise pigments, drying oils and additives that together confer desirable properties... more Oil paints comprise pigments, drying oils and additives that together confer desirable properties, but can react to form metal carboxylates (soaps) that may damage artworks over time. To obtain information on soap formation and aggregation, we introduce a new tapping‐mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopy and imaging on highly heterogenous and rough paint thin sections. PTIR is used in combination with µ‐computed tomography and IR microscopy to determine the distribution of metal carboxylates in a 23‐year old oil paint of known formulation. Results show that heterogeneous agglomerates of Al‐stearate and a Zn‐carboxylate complex with Zn‐stearate nano‐aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al‐stearate distribution. These measurements open a new chemically sensitive nanoscale observation window on the distribution of metal soaps that can bring insights for understanding soap formation in oil paint.
This research investigates and evaluates the optical, physical, and chemical interactions between... more This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.
For centuries, the architecture of the Palace Museum represented the highest standard of Chinese ... more For centuries, the architecture of the Palace Museum represented the highest standard of Chinese architecture. The Yangxin Palace of the Palace Museum consisted of 18 masonry buildings built using bricks, wood, roof tiles and various mortars. In 2016, a five-year project was initiated to work on the maintenance and restoration of the Yangxin Palace buildings. The characterization of the construction materials has become of primary importance, in order to obtain information about the raw ingredients and building technology of the mortars, and the history of possible previous restorations. In this paper, 12 different samples representing three types of mortar-based materials—namely, jointing mortars between the bricks on the wall, and surface plasters as well as mortars used on the roof—were collected for analysis from the Yanxi Hall of the Yangxin Palace. Analysis into the composition, grain-size distribution, organic and fibre additives and testing of the mortar density and water absorption were performed. Starch, protein and plant fibres were identified in some of the samples. Brucite, mullite and ettringite were detected within most mortars on the roof, possibly originating from the furnace slag added into the raw materials for restoration purposes. The analytical results will serve as a critical reference for the maintenance and restoration of the buildings in the Yangxin Palace.
The Yuzhen Palace is one of the nine palaces in the Ancient Building Complex built by order of th... more The Yuzhen Palace is one of the nine palaces in the Ancient Building Complex built by order of the Yongle Emperor during the Ming dynasty. The buildings were built with dressed black bricks. As a result of the planned national South–North Water Diversion project, the water level in the Danjiangkou Reservoir that surrounds the Yuzhen Palace was expected to rise by approximately 15 m. To avoid submersion of the site, three gates were elevated by 15 m in 2013 and other buildings dismantled, for later reconstruction. The characterization of the construction materials has therefore become of primary importance. Here, we present results on the plasters of the Longhu Hall. The analysis of materials involved a multi-analytical approach combining optical and electron microscopy with X-ray and vibrational spectromicroscopies and thermogravimetry. The results indicated the use of two earthen plaster layers and a whitewash finish coating applied over a thin preparatory intermediate layer to improve the adherence of the finish coating to the earthen plaster. Ramie and straw fibres identified in the earthen plasters were added to reduce shrinkage and cracking during drying. The raw materials used and the application technique pointed to a well-established construction industry using traditional earthen building materials together with lime technology.
Ammonium carbonate was used as the carbonation accelerator for air-hardening lime mortars in this... more Ammonium carbonate was used as the carbonation accelerator for air-hardening lime mortars in this study. Various analytical methods, including XRD, IR, TGA-DSC and SEM were employed to access the phase transformation, degree of carbonation and microstructural features of the lime-based mortars. The paper explores the correlation between the mechanical strength, microstructure of cured lime mortars and the composition/ carbonation degree with the crystallization behaviors in Ca(OH)2/CaCO3 binders. The results indicate that ammonium carbonate significantly accelerates the carbonation reaction and increases the early mechanical strength of air-hardening lime mortars. The mechanical strength of these modified lime mortars can be comparable to that of natural hydraulic lime (NHL). The aggregation behaviors of nano-CaCO3 under kinetic control, are believed to contribute much to the compact pore-structures and robust mechanical strength of lime mortars. This viable accelerating carbonation method holds promise for enhancing the properties of various limecontaining building materials in conservation and modern buildings.
Restoring ancient civilizations through cultural heritage conservation science Cultural heritage ... more Restoring ancient civilizations through cultural heritage conservation science Cultural heritage embodies the collective memory and identity of civilizations that have spanned centuries and continents. Understanding and preserving cultural heritage is of utmost importance as it provides invaluable insights into our past and serves as a bridge to the future. Cultural heritage conservation science employs a multidisciplinary approach that combines scientific research, technological advancements, and conservation ethics. It brings together experts from diverse academic fields such as materials science, chemistry, biology, civil engineering, geological sciences, architecture, archaeology, and history. By harnessing their knowledge and expertise, these professionals strive to restore ancient civilizations concealed within cultural artifacts and tackle the intricate challenges associated with safeguarding our cultural heritage. Fundamental aspects of cultural heritage conservation science encompass the study of cultural heritage materials, the development of conservation materials, and the implementation of conservation methodologies. The study of cultural heritage materials allows us to comprehend ancient civilizations and provides support for the application of materials and methods in cultural heritage conservation. Conservation materials are designed to aid ancient materials in retaining some of their original properties and mitigate further deterioration. The development and implementation of conservation methodologies aim to ensure the preservation, understanding, and appreciation of cultural heritage for both the present and the future. We are delighted to present this special topic of Science China Technological Sciences, dedicated to the captivating realm of cultural heritage conservation science. The objective of this issue is to shed light on the latest advancements and breakthroughs in this field. The topics covered encompass a broad array of themes, ranging from the development of new materials for conservation purposes to the application of innovative characterization techniques for analyzing cultural heritage materials. Moreover, the issue delves into the development and implementation of novel conservation methodologies, as well as the understanding of degradation phenomena in cultural heritage materials and sites. The materials addressed in this issue include earthen sites, bronzes, ceramic glazes, textiles, lacquerware, as well as the development of consolidants for stones and papers, and cleaning materials for paintings. Such comprehensive coverage reflects the extensive breadth and diversity of research in cultural heritage conservation science. Each contribution offers unique insights into the challenges faced by different cultural contexts, thereby providing a mosaic of knowledge that propels the field of cultural heritage conservation science forward. We invite you to embark on a captivating journey through the realm of cultural heritage conservation science, as illuminated by the articles in this special issue. Our hope is that this collection inspires scientists, conservation professionals, archaeologists, policymakers, and the wider public to recognize the value and urgency of cultural heritage conservation, as well as the significance of science and technology in restoring ancient civilizations. May this compilation ignite curiosity, spark meaningful conversations, and drive future research endeavors aimed at safeguarding our heritage for generations to come. We express our heartfelt gratitude to all the authors, reviewers, and editorial staff who have contributed their expertise, time, and unwavering dedication to shaping this special issue. Their collaborative spirit and commitment to excellence have ensured the high caliber of the research presented herein.
Cultural relics are man-made objects left from ancient times, with historical, artistic and scien... more Cultural relics are man-made objects left from ancient times, with historical, artistic and scientific values. Multi-interdisciplinary research of cultural relics would enable people to obtain a variety of information, from which the restoration of ancient civilization is possible. Due to natural weathering, many cultural relics are in a fragile state, and conservation treatments that can prolong their lifetime are important, which may involve the use of conservation materials. In this paper, we define the new term “Herit-Materials” as two type of materials, including ancient cultural relics themselves and novel functional materials for conservation purposes. For the first type of Herit-Materials- cultural relics themselves, as one type of ancient materials, the concept on the relationship between the structure, composition, performance and technology of them has been introduced, along with the research paradigm for ancient cultural relics. Following such a paradigm, the way how analysis and research has been performed on ancient cultural relics are illustrated in detail with examples of ancient ceramics and textile dyes. Meanwhile, as the second type of Herit-Materials, three categories of conservation materials, such as emergent conservation materials on archaeological sites, consolidation materials and cleaning materials have been reviewed in detail, including basic concepts, criteria for choosing appropriate materials for conservation purposes, evaluation of the conservation effects after application, along with the application methods of those conservation materials. Finally, as Herit-Materials’ studies have attracted many researchers and have also created new inter-disciplinary research fields, the following research directions are recommended for scholars who have interest, including the development of advanced and comprehensive analytical technique of Herit-Materials, non-destructive and in-situ characterization & testing of Herit-Materials, the database of composition-structure-performance for Herit-Materials and their real-time environmental conditions, the green Herit-Materials for conservation purposes and their application methods, as well as the type and pattern analysis research of Herit-Materials.
Lime mortars have taken an important role in constructing ancient Chinese masonry structures, inc... more Lime mortars have taken an important role in constructing ancient Chinese masonry structures, including city walls, buildings, and tombs. A tomb built with lime mortars and stones belonging a Ming high-rank official Xu Jie was discovered in Huzhou City of China. Eight different samples from Xu Jie’s tomb, representing four types of lime-mortar based materials: joint mortar between stone bricks, bedding mortar, grouting mortar, and plaster mortars were collected for analysis and comparison. The characterization of the construction materials has therefore become of primary importance. The function of each mortar was reported and studies into the micro-textural features and mineralogical compositions of those mortars were performed via a multi-analytical approach. The joint mortars were all found to be aerial lime mortars with predominately lime. The bedding mortar was found to consist of lime, soil and sand, typical of a tabia mortar. The grouting mortar was found to consist of lime and ground contact metamorphosed limestone. Analysis of plaster sample taken from the roof of the main tomb identified the presence of calcium stearate/palmitate, indicating the usage of plant-based Tung oil as an additive. The analytical results will promote our understanding of Ming architectural technology and craftsmanship, and provide critical information for the conservation of Xu Jie’s tomb.
This research investigates and evaluates the optical, physical, and chemical interactions between... more This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into cal...
ABSTRACT This research develops hydroxyapatite (HAP)-based, inorganic mineral systems for the con... more ABSTRACT This research develops hydroxyapatite (HAP)-based, inorganic mineral systems for the consolidation of powdery wall paintings of archaeological significance. The scientific approach exploits biomimetic (biologically inspired design) principles to induce in situ the formation of protective HAP crystals by triggering reactions between the calcium carbonate-rich layers in wall paintings and ammonium phosphate precursors. The high solubility and absence of toxicity of ammonium phosphate precursors and the stability of the hydroxyapatite reaction product at varying pH, renders this treatment extremely promising for consolidation and protection of weathered wall paintings. Experimental trials were carried out on wall painting test blocks applying cellulose compresses of 1M and 2M solutions of diammonium hydrogen phosphate for 3 to 6 hours contact time. The consolidating effect was evaluated through microstructurally and compositionally-sensitive analytics including VPSEM-EDS, XRF, water sorption test and scotch tape test. Preliminary results indicated the formation of a porous hydroxyapatite network at the surface and subsurface of the test blocks with improved cohesion, pH-resistivity and reduced water absorption. These data show the potential of this treatment for the consolidation of powdery wall paintings and their protection from weathering and deterioration induced by natural aging and environmental action-linked effects.
Formation and aggregation of metal carboxylates (metal soaps) can degrade the appearance and inte... more Formation and aggregation of metal carboxylates (metal soaps) can degrade the appearance and integrity of oil paints, challenging efforts to conserve painted works of art. Endeavors to understand the root cause of metal soap formation have been hampered by the limited spatial resolution of Fourier transform infrared microscopy (μ-FTIR). We overcome this limitation using optical photothermal infrared spectroscopy (O-PTIR) and photothermal-induced resonance (PTIR), two novel methods that provide IR spectra with ≈500 and ≈10 nm spatial resolutions, respectively. The distribution of chemical phases in thin sections from the top layer of a 19th-century painting is investigated at multiple scales (μ-FTIR ≈ 10 2 μm 3 , O-PTIR ≈ 10 −1 μm 3 , PTIR ≈ 10 −5 μm 3). The paint samples analyzed here are found to be mixtures of pigments (cobalt green, lead white), cured oil, and a rich array of intermixed, small (often ≪ 0.1 μm 3) zinc soap domains. We identify Zn stearate and Zn oleate crystalline soaps with characteristic narrow IR peaks (≈1530−1558 cm −1) and a heterogeneous, disordered, water-permeable, tetrahedral zinc soap phase, with a characteristic broad peak centered at ≈1596 cm −1. We show that the high signal-to-noise ratio and spatial resolution afforded by O-PTIR are ideal for identifying phase-separated (or locally concentrated) species with low average concentration, while PTIR provides an unprecedented nanoscale view of distributions and associations of species in paint. This newly accessible nanocompositional information will advance our knowledge of chemical processes in oil paint and will stimulate new art conservation practices.
The characterization of lime mortars has become of primary importance in order to obtain informat... more The characterization of lime mortars has become of primary importance in order to obtain information about the raw ingredients and building technology of ancient masonry structures. Five different samples from Anhui province, China, representing two types of lime mortar‐based materials: joint mortars between the bricks of the city wall and lime mortar sealing a tomb coffin, were collected for analysis. Archaeological information about the samples was reported and studies into the microtextural features and mineralogical compositions of those mortars were performed via a multi‐analytical approach. The joint lime mortars between the bricks of city walls, including Mingzhongdu city wall, Mingzhongdu Xihua gate foundation, Zhengyangguan city wall and She county city wall, were found to be aerial lime mortars. The lime mortar from Nanling Tieguai Song dynasty tomb was analysed and found to be a pozzolanic mortar consisting of lime, clay, sand and cocciopesto‐like materials. The analytical results serve as a critical reference for the maintenance and restoration of ancient city walls in Anhui province, and as a starting point for searching for ancient Chinese pozzolanic mortars and technology for making those mortars.
A theoretical and experimental approach was applied to investigate phase relations in a system co... more A theoretical and experimental approach was applied to investigate phase relations in a system containing calcium carbonate and different ammonium phosphate solutions. Using laboratory experiments and thermodynamic modeling, this paper provides an insight into the formation of stable phase assemblages in the calcium carbonate and mono‐, di‐, triammonium phosphate aqueous system. Focus is placed on the morphological and mineralogical characterization and thermodynamic calculation of calcium phosphates precipitating due to the reaction between the calcium carbonate and ammonium phosphate solutions. Correlations between the formed stable calcium phosphate phases and the ammonium phosphate precursors are provided. Advantages and limitations of various analytical and modeling techniques used in this study such as geochemical equilibrium‐based modeling, X‐ray diffraction, scanning electron microscopy, and thermal analysis, are critically evaluated. Additionally, possible impacts of the ammonium phosphate solution type on the kinetics of phase transformations are discussed.
Materials in the paint layers of an early sixteenth-century painted and glazed terracotta sculptu... more Materials in the paint layers of an early sixteenth-century painted and glazed terracotta sculpture by Giovanni della Robbia, Pietà were identified. The presence of the rare lead chloride salts, cotunnite (PbCl2) and challacolloite (KPb2Cl5), were confirmed using Raman spectroscopy and electron back scatter diffraction. Well-formed habit of large crystals of challacolloite indicates slow growth from solution. The stability and potential pathways for the in-situ formation of lead chloride compounds are discussed. The presence of lead chloride phases in the Pietà indicates conditions of high chloride ion concentrations (i.e., activities) and/or low pH led to the alteration of the pigment lead white (hydrocerussite, 2PbCO3·Pb(OH)2). This work highlights the role of ion transport in alteration of artists’ materials and emphasizes the importance of considering the role of treatments and envi-ronmental factors in changes in materials, and reinforces our awareness of the on-going chemistry occurring in works of art.
Oil paints comprise pigments, drying oils and additives that together confer desirable properties... more Oil paints comprise pigments, drying oils and additives that together confer desirable properties, but can react to form metal carboxylates (soaps) that may damage artworks over time. To obtain information on soap formation and aggregation, we introduce a new tapping‐mode measurement paradigm for the photothermal induced resonance (PTIR) technique that enables nanoscale IR spectroscopy and imaging on highly heterogenous and rough paint thin sections. PTIR is used in combination with µ‐computed tomography and IR microscopy to determine the distribution of metal carboxylates in a 23‐year old oil paint of known formulation. Results show that heterogeneous agglomerates of Al‐stearate and a Zn‐carboxylate complex with Zn‐stearate nano‐aggregates in proximity are distributed randomly in the paint. The gradients of zinc carboxylates are unrelated to the Al‐stearate distribution. These measurements open a new chemically sensitive nanoscale observation window on the distribution of metal soaps that can bring insights for understanding soap formation in oil paint.
This research investigates and evaluates the optical, physical, and chemical interactions between... more This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.
For centuries, the architecture of the Palace Museum represented the highest standard of Chinese ... more For centuries, the architecture of the Palace Museum represented the highest standard of Chinese architecture. The Yangxin Palace of the Palace Museum consisted of 18 masonry buildings built using bricks, wood, roof tiles and various mortars. In 2016, a five-year project was initiated to work on the maintenance and restoration of the Yangxin Palace buildings. The characterization of the construction materials has become of primary importance, in order to obtain information about the raw ingredients and building technology of the mortars, and the history of possible previous restorations. In this paper, 12 different samples representing three types of mortar-based materials—namely, jointing mortars between the bricks on the wall, and surface plasters as well as mortars used on the roof—were collected for analysis from the Yanxi Hall of the Yangxin Palace. Analysis into the composition, grain-size distribution, organic and fibre additives and testing of the mortar density and water absorption were performed. Starch, protein and plant fibres were identified in some of the samples. Brucite, mullite and ettringite were detected within most mortars on the roof, possibly originating from the furnace slag added into the raw materials for restoration purposes. The analytical results will serve as a critical reference for the maintenance and restoration of the buildings in the Yangxin Palace.
The Yuzhen Palace is one of the nine palaces in the Ancient Building Complex built by order of th... more The Yuzhen Palace is one of the nine palaces in the Ancient Building Complex built by order of the Yongle Emperor during the Ming dynasty. The buildings were built with dressed black bricks. As a result of the planned national South–North Water Diversion project, the water level in the Danjiangkou Reservoir that surrounds the Yuzhen Palace was expected to rise by approximately 15 m. To avoid submersion of the site, three gates were elevated by 15 m in 2013 and other buildings dismantled, for later reconstruction. The characterization of the construction materials has therefore become of primary importance. Here, we present results on the plasters of the Longhu Hall. The analysis of materials involved a multi-analytical approach combining optical and electron microscopy with X-ray and vibrational spectromicroscopies and thermogravimetry. The results indicated the use of two earthen plaster layers and a whitewash finish coating applied over a thin preparatory intermediate layer to improve the adherence of the finish coating to the earthen plaster. Ramie and straw fibres identified in the earthen plasters were added to reduce shrinkage and cracking during drying. The raw materials used and the application technique pointed to a well-established construction industry using traditional earthen building materials together with lime technology.
Magnesium matrix composites with AlN and Mg2Si reinforcement are potential engineering materials ... more Magnesium matrix composites with AlN and Mg2Si reinforcement are potential engineering materials for automobile and aerospace applications. Fine particulate AlN/Mg composites have been successfully in-situ synthesized using Mg alloy and Al shots and Si3N4 powder as raw materials. Reaction under argon atmosphere or SF6/CO2 protective gas atmosphere at 770 to 850°C for an hour was used to produce composites containing different volume fraction of AlN (+ residual Mg2Si) depending on the reaction temperature. The microstructures were characterized using X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy. Fine AlN particles embedded within magnesium matrix in addition to a larger size Mg2Si phase was observed after the in-situ reaction. The AlN particles were found to have formed from the prior Si3N4 agglomerates while the morphology of the Mg2Si phase was dependent upon the composition, temperature and cooling rate. Thermodynamic calculations including the equilibrium and Scheil solidification paths of the resultant alloy after the in situ reaction were performed and compared. At the same time, reaction mechanism was studied using SEM and TEM and a “core-shell” reaction mechanism was supported.
This paper focuses on the characterization of materials from fragmented pieces of an imperial lac... more This paper focuses on the characterization of materials from fragmented pieces of an imperial lacquer plate in the Luozhuang Han tomb, which dates to the early Western Han dynasty. Various non-invasive and minimally invasive techniques were performed, including optical and electron microscopy, XRF, Raman spectromicroscopy, FT–IR, XRD and THM-Py–GC/MS. The lacquerware pieces consist of a five-layer structure, which includes (from the top): a red pigmented layer, two lacquer finish layers, a ground layer and a canvas/wood foundation layer. The red layer consists of ground cinnabar mixed with urushi. The lacquer finish layers are made of urushi mixed with perilla or tallow tree oil, without any pigment. The ground layer is a mixture of organic materials including urushi, tree oil and amorphous carbon
Earthen built materials are one of the most widely used construction materials in the world. Howe... more Earthen built materials are one of the most widely used construction materials in the world. However, due to the nature of the earthen materials, they are susceptible to deterioration. In this entry, the components, properties and preparation techniques of the earth materials are covered. The pathologies of the earthen materials, including non-structural and structural damages, as well as the factors that lead to the deterioration of earthen materials, including environmental factors, human and animal activity and external factors are discussed in detail.
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Thermodynamic calculations including the equilibrium and Scheil solidification paths of the resultant alloy after the in situ reaction were performed and compared. At the same time, reaction mechanism was studied using SEM and TEM and a “core-shell” reaction mechanism was supported.