Study on the Characteristics of Materials and Manufacturing Techniques for the Mural Paintings in Daeunjeon at Ssanggyesa Temple, Jindo

This study identifies the structure and material characteristics of the mural paintings in Daeungjeon at Ssanggyesa temple in Jindo by conducting scientific research and analysis including microscope examination, SEM-EDS, XRD, particle size analysis, and others. According to the analyses, the murals were considered to be of a typical soil mural style for Korean Buddhist murals, given that the walls were made of sand and soil and the murals had layers consisting of wall layers and a finishing layer. However, some finishing layer used calcite, while some ground layer used zinc white beneath the thick paint. In addition, there were similar features to those found on the surfaces of oil paintings such as cracks along with the paint layer, high gloss on surfaces, and thick brush strokes in many areas. It was found that the walls on which the murals were painted were made of soil but that the paint layer was created based on the oil painting technique using drying oil. It determined that the murals were painted in a unique painting style that is rarely found in other typical Buddhist murals in Korea.

Features of the restoration of Buddhist thangka

Цель статьи — познакомить реставраторов и исследователей с традиционными и современными методами реставрации буддийской живописи на холсте, c оборудованием и материалами, которые применяются в лаборатории научной реставрации восточной живописи Государственного Эрмитажа. Актуальность данной работы продиктована развитием реставрационной практики буддийской живописи в последние десятилетия. В исследовании показано, как появление новых высокотехнологичных материалов, оборудования и методов исследования памятников позволяет реставратору более эффективно работать с ними. Также в данной работе показаны результаты изучения и исследования двух тангка. Комплексное исследование тангка, проведенное силами специалистов научно-исследовательских лабораторий, позволило правильно выбрать методики реставрации. Кроме этого, в работе приводятся краткие исторические сведения об иконографии и технологии создания тангка. В статье проводится анализ реставрационных методик и их выбора, рассматриваются этические проблемы, связанные с допустимой степенью вмешательства в структуру памятника. На примере сравнения подходов к реставрации двух буддийских тангка, реставрированных в разные годы (тангка «Образ буддийский Дорджэ Лэкпа» в 2018 году и тангка «Махакала синий шестирукий, трехглазый, стоящий на слоне с человеческой фигурой» в 2021 году), описаны различные методики. Анализ проведенных реставрационных мероприятий включает в себя описание проведенных исследований памятников до реставрации и методов отчистки поверхности, укрепления красочного слоя, восполнения грунта, выравнивания основы и восполнения утрат красочного слоя. В статье показана практическая значимость и результативность применения различных материалов, оборудования и методов реставрации буддийской живописи. Обобщены результаты реставрации обоих памятников. The aim of the article is to acquaint restorers and researchers of Buddhist painting on canvas with traditional restoration methods combined with modern equipment and materials that are used in the Laboratory of Scientific Restoration of Oriental Painting of the State Hermitage Museum. The relevance of this work is dictated by the development restoration practice of Buddhist painting in recent decades. It is shown in the study how the emergence of new high-tech materials, equipment and methods of studying monuments allows the restorer to work with them more effectively. Also in this paper, the results of the study and study of two thangkas are shown. Comprehensive the thangka study conducted by the specialists of research laboratories made it possible to choose the right restoration techniques. In addition, a brief work of historical information about the iconography and technology of creating a thangka is provided. The restoration techniques and their choices are analyzed in the article. Also the ethical problems related to the permissible degree of interference in the structure of the monument are examined. Using the example of comparing approaches to the restoration of two Buddhist thangkas restored in different years: the “Dorje Lakpa Buddhist Image” thangka in 2018, and the “Mahakala blue, 6-handed, 3-eyed, standing on an elephant with a human figure” thangka in 2021, various techniques are described. The analysis of the restoration measures carried out includes a description of the studies carried out on the monuments before the restoration, and methods of cleaning the surface, strengthening the paint layer, replenishing the soil, leveling the base and replenishing the losses of the paint layer. The article shows the practical significance and effectiveness of the use of various materials, equipment and methods of restoration of Buddhist painting. In conclusion, the results of the restoration of both monuments are summarized.

Nondestructive Tomographic Imaging of Rust with Rapid THz Time-Domain Spectroscopy

In this study, we developed a rapid nondestructive tool for testing rust spread in a metal covered by a paint layer by using a THz time-domain spectroscopy system at a speed of 100 Hz/pixel. Time-of-flight imaging helps identify rust formation by exclusively obtaining the reflection from the steel below the paint surface. The use of frequency-selective imaging allows us to manipulate the contrast in rust imaging. Higher contrast is generally obtained when monitoring using the higher frequency component. In addition, we monitored the spread of rust in a steel plate under the influence of two different chemical solutions: NaCl and acid. We found that in the early stages, the decrease in THz reflection was governed by the high-frequency components due to the formation of lepidocrocite, whereas the low-frequency component develops as the proportion of hematite increases with time.

Paper trapping research after adding Mulberry tree branches bark cellulose pulp

The paper presents the study results of paper trapping during inkjet printing which contains cellulose pulp from the inner bark layer of mulberry branches. The connection between the print density and the paper surface structure, in particular, water absorption and raggedness, is established. The study of the stepwise gradation transition and color rendition, the graphic accuracy of reproduction of the slur element of the image is carried out. Densitometric and microscopic analysis of the impressions printed on an inkjet printer was performed. It was revealed that the pigments of water ink, depending on the microgeometry of the paper surface, penetrated deeper in different ways. It was found that the maximum thickness of the paint layer, expressed using the optical density values for the primary colors of the subtractive synthesis, and the best color reproduction were provided by the surface of the paper sample with 100 % addition of cellulose pulp from the inner layer of the bark of mulberry tree branches, which has the least roughness, according to the scanning probe microscope Solver HV. Recommendations are given for testing paper data on inkjet printers that use pigment inks and are less demanding on the surface properties of paper, or by printing methods that do not use low-viscosity printing inks.

LIBS Monitoring and Analysis of Laser-Based Layered Controlled Paint Removal from Aircraft Skin

Reliability and controllability of selective removal of multiple paint layers from the surface of aircraft skin depend on effective online monitoring technology. An analysis was performed on the multi-pulse laser-induced breakdown spectroscopy (LIBS) on the surface of the aluminum alloy substrate, primer, and topcoat. Based on that, an exploration was conducted on the changes of the characteristic peaks corresponding to the characteristic elements that are contained in the topcoat, primer, and substrate with different layers of a laser action, in combination with analysis of microscopic morphology, composition, and depth of laser multi-pulse pits. The results show that the appearance and increase of the characteristic peak intensity of the Ca I at the wavelength of 422.7 nm can be regarded as the basis for the complete removal of the topcoat; the decrease or disappearance of the characteristic peak intensity can be regarded as the basis for the complete removal of the primer. Al I spectrum at the wavelength of 394.5 nm and 396.2 nm can be adopted to characterize the degree of damage to the aluminum alloy substrate. The feasibility and accuracy of the LIBS technology for the laser selective paint removal process and effect monitoring of aircraft skin were verified. Demonstrating that under the premise of not damaging the substrate, laser-based layered controlled paint removal (LLCPR) from aircraft skin can be achieved by monitoring the spectrum and composition change law of specified wavelength position corresponding tothe characteristic elements that are contained in the specific paint layer.

Polychrome arhat figures dated from the Song Dynasty (960–1279 CE) at the Lingyan Temple, Changqing, Shandong, China

Scientific analysis revealed the materials and techniques used in the process of making polychrome sculptures providing a solid foundation for the protection and restoration of the painted statues. In addition, the analyses revealed changes in colour schemes applied to the sculptures can provide the basis for the virtual restoration of the painted statues. In order to carry out scientifically-informed protection and restoration of the Bodhidharma statue from the Lingyan Temple, Changqinq, Shandong, several analytical methods such as optical microscope (OM), Micro-Raman spectroscopy (μ-RS), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDS) and Fourier transform infrared spectroscopy (FTIR) were employed. Analyses clearly reveal the information including the stratigraphic structure and the composition of pigment. The use of silver foils and golden yellow pyrophyllite mineral to replace gold foils were found in the gilding paint layer in the later repainting after the Song Dynasty. This work reports the coexistence of emerald green (Cu(C2H3O2)2·3Cu(AsO2)2) and the degradation product lavendulan (NaCaCu5(AsO4)4Cl·5H2O) in large areas of the paint stratigraphy and on the surface confirming that the degradation of emerald green is related to the thickness of the paint layer; in thinner paint layers emerald green is transformed in lavendulan, while thicker layers of contain both lavendulan and emerald green, suggesting an environmental source of chlorides.

Biodeterioration of Salón de Reinos, Museo Nacional del Prado, Madrid, Spain

The Salón de Reinos, a remnant of the 17th century Palacio del Buen Retiro, was built as a recreational residence under the reign of Felipe IV between 1632 and 1640 and was the main room for the monarch’s receptions. This Salón owes its name to the fact that the coats of arms (shields) of the 24 kingdoms that formed Spain in Felipe IV’s time were painted on the vault, above the windows. In addition, the ceiling shows an original decorative composition. The painted ceiling and window vaults showed deterioration evidenced by fissures, water filtration, detachments of the paint layer, and black stains denoting fungal colonization related to humidity. Ten strains of bacteria and 14 strains of fungi were isolated from the deteriorated paintings. Their biodeteriorative profiles were detected through plate assays. The most frequent metabolic functions were proteolytic and lipolytic activities. Other activities, such as the solubilization of gypsum and calcite and the production of acids, were infrequent among the isolates.

Three-dimensional numerical and experimental study of fracture saturation in panel paintings

Panel paintings—complex multi-layer structures consisting of wood support and a paint layer composed of a preparatory layer of gesso, paints, and varnishes—are among the category of cultural objects most vulnerable to relative humidity fluctuations and frequently found in museum collections. The current environmental specifications in museums have been derived using the criterion of crack initiation in an undamaged, usually new gesso layer laid on wood. In reality, historical paintings exhibit complex crack patterns called craquelures. The present paper analyses the structural response of a paint layer with a virtual network of rectangular cracks under environmental loadings using a three-dimensional model of a panel painting. Two modes of loading are considered—one induced by one-dimensional moisture response of wood support, termed the tangential loading, and the other isotropic induced by drying shrinkage of the gesso layer. The superposition of the two modes is also analysed. The modelling showed that minimum distances between cracks parallel to the wood grain depended on the gesso stiffness under the tangential loading. Despite a nonzero Poisson’s ratio, gesso cracks perpendicular to the wood grain could not be generated by the moisture response of the wood support. The isotropic drying shrinkage of gesso produced cracks that were almost evenly spaced in both directions. The modelling results were cross-checked with crack patterns obtained on a mock-up of a panel painting exposed to several extreme environmental variations in an environmental chamber.

Substrate Cleaning Threshold for Various Coated Al Alloys Using a Continuous-Wave Laser

In this study, different coatings (gray epoxy primer, white epoxy varnish and red alkyd paint) of 7075 aluminum alloy are cleaned with a 500 W continuous-wave (CW) fiber laser. We analyzed the influence of the laser power density on the temperature evolution and target surface morphology. Under the condition of continuous laser irradiation for 1 s, the experimental results indicated that the suitable cleaning thresholds of epoxy primer, epoxy primer and epoxy varnish, as well as epoxy primer, epoxy varnish and alkyd paint were 177.74, 192.89 and 147.44 W/mm2. The results show that the cleaning threshold of thicker three-layer paint target was smaller than the single-layer paint layer, and we analyze the mechanism of this phenomenon.

The stability of paintings and the molecular structure of the oil paint polymeric network

A molecular-level understanding of the structure of the polymeric network formed upon the curing of air-drying artists’ oil paints still represents a challenge. In this study we used a set of analytical methodologies classically employed for the characterisation of a paint film—based on infrared spectroscopy and mass spectrometry—in combination with solid state NMR (SSNMR), to characterise model paint layers which present different behaviours towards surface cleaning with water, a commonly applied procedure in art conservation. The study demonstrates, with the fundamental contribution of SSNMR, a relationship between the painting stability and the chemical structure of the polymeric network. In particular, it is demonstrated for the first time that a low degree of cross-linking in combination with a high degree of oxidation of the polymeric network render the oil paint layer sensitive to water.