Search Results (93)

Plant gums have long served as essential binding media in polychrome cultural heritage, contributing to pigment adhesion, surface cohesion, and long-term stability. This review evaluates recent advances in analytical technologies, including FTIR, Raman spectroscopy, GC-MS, LC-MS/MS, MALDI-TOF MS, hyperspectral imaging, and immunological assays, for the identification of gums such as gum arabic, peach gum, and tragacanth in diverse cultural contexts. Drawing on case studies from 19th-century watercolours, ancient Egyptian coffins, and Maya murals, the paper demonstrates how these methods enable precise chemical characterization even in complex, aged, and mineral-rich matrices. Such information directly aids conservators in selecting compatible restoration materials, tailoring treatment protocols, and assessing deterioration mechanisms. Persistent challenges remain, including gum degradation, spectral interference from pigments and restoration materials, sample heterogeneity, and limited reference libraries, particularly for non-European species. Future research directions emphasize multi-modal, non-invasive workflows that integrate hyperspectral imaging with spectroscopic and chromatographic methods, drone-assisted micro-Raman for inaccessible surfaces, machine learning-assisted spectral databases, and bio-inspired adhesives replicating historical rheology. By linking molecular identification to conservation decision-making, plant gum analysis not only deepens our understanding of historical material practices but also strengthens the scientific basis for sustainable heritage preservation strategies. Full article

The conservation and restoration of water-gilded wooden cultural heritage, such as polychrome sculptures, frames, panels, altarpieces, etc., requires the use of fillers that guarantee structural stability, physicochemical and mechanical compatibility with the original support, and the ability to adapt to dimensional movements induced by thermo-hygrometric variations. This study, conducted as part of the DorART Project, analyzed the behavior of nine formulations, both commercial and non-commercial, selected through a review of the state-of-the-art specialized literature, along with the use of participatory science, which focused on the practices and materials most commonly used by professionals in the field. The experimental design was based on three types of specimens: two with wooden supports, selected for evaluating their interaction with the original material and with the traditional water gilding technique, and a third type for analyzing the individual behavior of the tested materials. Analyses of adhesion, tensile strength, Shore C hardness, gloss, abrasion test results, wettability, pH changes, and chemical composition were performed using ATR-FTIR spectroscopy. The results showed significant differences depending on the type of curing used and the composition and aging behavior of the specimen. Some of the fillers demonstrated improved compatibility with water-based gilding, facilitating workability and providing structural strength. M3 and M9 demonstrated an optimal balance of workability and aging stability. The results of this study can help restorers select materials based on their specific needs, considering the requirements of mechanical adaptation to the substrate, compatibility, and durability. Full article

This study investigates the application of terahertz frequency-modulated continuous-wave (FMCW) imaging for the non-destructive inspection of a historical enamel plate, using both reflection and transmission modes. A 300 GHz FMCW radar system was employed to capture high-resolution images of the plate’s internal and surface structures. Through optimized data acquisition and processing, the system successfully revealed subsurface features such as fractures, as well as surface-level textural variations linked to the decorative glazes. Although pigment differentiation remains a challenge, contrast variations observed in THz images suggest correlations with material composition. The results highlight the potential of FMCW terahertz imaging as a compact, rapid, and non-contact diagnostic tool for cultural heritage analysis. Its practicality and adaptability make it particularly suitable for in situ inspections in museums or restoration contexts. Full article

Paquimé is a remarkable pre-Hispanic settlement that flourished between the 13th and 15th centuries in northwest Chihuahua, Mexico. This site is recognized for its distinctive fusion of Mesoamerican and Southwestern American cultural traits. Although much of the explanatory models about this settlement’s development and regional role have focused on trade, pottery from the Salado tradition, particularly Polychrome Gila and Polychrome Tonto, has generally been presumed to have originated in the American Southwest. To confirm the interaction between both cultures and contribute to the clarification of the absolute chronology of Paquimé, the geochemical characterization and rock-magnetic characterization of sherds of local and presumably foreign manufacture were carried out, including sherds with manufacture that seems to be the result of the abovementioned relationship. SiO₂ and Al₂O₃ contribute more than 75% to the observed variation. The Casas Grandes pottery shares the geochemical signatures of both local and foreign types. High-coercivity magnetic grains dominate in the foreign-type pottery samples. In contrast, relatively low-coercivity ferrimagnetic grains are the main features of local-type sherds. Essentially similar absolute intensity values were obtained for both potsherd wares. The most probable age intervals obtained for all ceramic samples studied range from 990 AD to 1310 AD, in agreement with previous surveys and local archaeological frameworks. Full article

This study presents the first scientific characterization of the white preparatory layer and polychrome pigments on painted wooden figurines excavated from the Mawangdui Tomb No. 1, dating to the Han dynasty. A combination of analytical techniques, including XRF mapping, SEM, ATR-FTIR, XRD, and Raman spectroscopy, was used to investigate the composition, structure, and potential additives in the white layer. The results reveal that the preparatory layer is primarily composed of gypsum (CaSO₄·2H₂O) and calcite (CaCO₃), with minor phases such as anhydrite and larnite. SEM observations show a porous microstructure of needle-like crystals, while spectroscopic data suggest possible traces of organic binders. The preparatory layer was likely applied to smooth surface irregularities and support polychrome decoration, such as cinnabar and carbon-based pigments, and may have also functioned as a putty in localized areas. This represents the first confirmed use of gypsum-based plaster in ancient Chinese woodcarving, showing unexpected parallels with surface preparation techniques used in New Kingdom Egypt. However, the presence of organic additives and the internal structure of the figurines remain unresolved due to equipment limitations. These findings provide new insights into ancient material practices and highlight the importance of environmental control and material-specific conservation strategies for fragile gypsum-based heritage objects. Full article

In India, particularly in central India, a large number of early images were created using green pigments. Within the green images or images in the earliest style, one can see that some extremely naturalistic animal figures were made with green and dark red, and rarely in a polychrome (green, red and yellow) style. Only a few images have survived. The human figures, represented in a typical S shape in a smaller size or with an S-twist body in single outline, are highly artistic and very dynamic figures. The figures are mostly represented as dancers. Wakankar found green pigment in the Upper Paleolithic levels in Bhimbetka, and hence these images were put in the Upper Paleolithic period. These green images mainly exist in rock art sites in the surroundings of Bhimbetka in the Raisen, Sehore and Vidisha districts. Full article

This paper presents the technical design of the pathfinder Barcelona Raman LIDAR (pBRL) for the northern site of the Cherenkov Telescope Array Observatory (CTAO-N) located at the Roque de los Muchachos Observatory (ORM). The pBRL is developed for continuous atmospheric characterization, essential for correcting high-energy gamma-ray observations captured by Imaging Atmospheric Cherenkov Telescopes (IACTs). The LIDAR consists of a steerable telescope with a 1.8 m parabolic mirror and a pulsed Nd:YAG laser with frequency doubling and tripling. It emits at wavelengths of 355 nm and 532 nm to measure aerosol scattering and extinction through two elastic and Raman channels. Built upon a former Cherenkov Light Ultraviolet Experiment (CLUE) telescope, the pBRL’s design includes a Newtonian mirror configuration, a coaxial laser beam, a near-range system, a liquid light guide and a custom-made polychromator. During a one-year test at the ORM, the stability of the LIDAR and semi-remote-controlled operations were tested. This pathfinder leads the way to designing a final version of a CTAO Raman LIDAR which will provide real-time atmospheric monitoring and, as such, ensure the necessary accuracy of scientific data collected by the CTAO-N telescope array. Full article

Cultural heritage objects, including traditional Chinese polychrome paintings on architectures (Caihua) and wooden architectural components, frequently exhibit surface defects that are highly sensitive to environmental factors, resulting in progressive deterioration. However, due to limited data acquisition methods and quantitative analysis models, the stability and risks of defects such as cracks during environmental changes remain unclear. This study integrates photogrammetry and digital image processing to investigate through-cracks and craquelures on the surface of a well pavilion within the Palace Museum, Beijing. We confirmed the activity of these cracks, quantified crack widths, and studied the environmental influences on their development. Over a monitoring period of more than 15 months, the widths of seven cracks on four beams were measured alongside various environmental factors. Correlation analyses identified air humidity as the most significant factor influencing crack width fluctuations (p < 0.01). Numerical simulations revealed that short-term humidity exposure induces surface swelling and crack closure, whereas prolonged humidity leads to internal moisture transport and crack reopening. Furthermore, fitting parameters indicating the severity of crack variation correlated well with the degradation levels of the wooden components. In summary, this study establishes a monitoring and quantification procedure for assessing crack activity, explores the influence of humidity through numerical simulations, and identifies a potential indicator for the non-destructive assessment of timber component stability. The proposed framework offers an exploratory approach to addressing critical challenges in the health monitoring of wooden architectural components. Full article

Hangzhou was the political and economic center of the Southern Song Dynasty (1127–1279 AD) and also the southern end of the Beijing-Hangzhou Grand Canal during the Ming and Qing Dynasties (1368–1644 AD). This historical position allowed the city’s economy to develop rapidly and influenced the form of its polychrome paintings with the imperial official style of the north China. However, due to the high temperature and rainy natural preservation conditions, southern polychrome paintings have always been a weak link in Chinese architectural polychrome painting craftsmanship. This study focuses on two well-preserved official-style architectural polychrome paintings in the grand halls from the late Qing period in Hangzhou. Through multi-techniques such as optical microscopy (OM), scanning electron microprobe with energy dispersive X-ray spectroscopy analysis (SEM-EDX), micro-Raman spectroscopy, micro-Fourier Transform Infrared spectroscopy (μ-FTIR), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), it was found that there is a significant difference from the reported common non-ground architectural paintings in the south, typically having four-layer structures with a white base and ground plaster layer in preparation for painting. The appearance of pigments such as artificial ultramarine (Na₆Al₄Si₆S₄O₂₀) and emerald green (Cu(C₂H₃O₂)₂·3Cu(AsO₂)₂) indicates that the paintings were made at least after the 1830s, and the use of malachite green dye and copper phthalocyanine blue (PB 15:X) suggests that unrecorded restorations were also performed after the 20th century. All samples are coated with a layer of alkyd resin, which may have been added during the repairs in the latter half of the 20th century, leading to the black discoloration of the present paintings, especially in areas where emerald green was used. This study provides an important case for the study of the official style of polychrome painting craftsmanship in the southern region of China and also offers important references for the future protection and restoration of traditional architectural polychrome painting. Full article

This article explores recent advancements in non-destructive spectroscopic techniques for identifying pigments in polychrome cultural relics, emphasizing their significance for sustainability in cultural heritage preservation. Techniques such as infrared spectroscopy, Raman spectroscopy, and X-ray fluorescence spectroscopy facilitate the accurate identification of pigment compositions while ensuring the integrity of the artifacts is maintained. Our findings indicate that integrating multiple spectroscopic methods enhances the accuracy of pigment identification and deepens our understanding of the structural and preservation status of historical artifacts. We also outline future directions for spectroscopic analysis in the field of cultural heritage, including micro-area analysis, data fusion, and intelligent data processing, aimed at improving the efficiency and effectiveness of pigment identification, ultimately contributing to the sustainable preservation of cultural assets. Full article

This study examines the effects of drying oils—Tung and linseed—on the properties of traditional polychrome coatings applied to wood. Samples prepared with cinnabar, malachite green, yellow ochre, and azurite pigments were analyzed using colorimetric, gloss measurements, surface roughness testing, adhesion strength, and SEM imaging. The results show that Tung oil generally enhances gloss by over 20% and provides superior adhesion, consistently achieving an adhesion grade of 0 (no peeling) across all pigments. Linseed oil, although effective at higher concentrations, displayed more variable adhesion, particularly with blue and yellow pigments. Surface roughness measurements revealed that higher oil content (6:4 ratio) reduced roughness, achieving smoother finishes with Ra values as low as 2.36 μm for Tung oil. SEM analysis confirmed that Tung oil yields a smoother and more even pigment distribution compared to the rougher, clustered morphology in linseed oil samples. These findings underscore the importance of oil type and concentration in achieving desired esthetic and durability outcomes in restoration work. Full article

The interior of Orthodox churches is entirely decorated with paintings, icons, and frescoes, to help create a special environment for the prayers and visitors. The paintings have religious, esthetic, and historical value, being created in the Byzantine tradition and following recommendations on style and materials according to old church canons. Particular importance is attributed to the Iconostasis decorated with icons on several registers, as well as to polychrome wooden ornaments and imperial doors. This work presents the scientific investigation results of three royal icons, theoretically dating to the 19th century, from the Iconostasis of the Runcu church, an important 19th-century Romanian historical monument, aiming to answer questions regarding their age and constituent materials, especially what were the mineral pigments used in the color palettes for their painting and if there were any old repainting interventions, in order to assist their restoration and conservation. Methods of characterization employed were optical microscopy, SEM-EDX spectrometry, ATR/FTIR spectroscopy, and X-ray fluorescence spectrometry. Results obtained allowed us to date, attribute, and evaluate the conservation state of the Royal icons; to our knowledge, this study is among the very few research studies carried out so far on the religious heritage conservation field in Romania. Full article

On the surface of the Cave of Altamira’s prehistoric paintings, a series of active deterioration processes are evident, leading to significant alterations of this invaluable heritage. This study proposes a comprehensive methodology for the systematic recording and management of these alterations. To achieve this, advanced microphotogrammetric monitoring techniques are employed, allowing for the acquisition of very high-resolution images that provide objective and quantifiable data that let us determine the evolution of the alterations. By comparing these images with those from earlier campaigns, the study tracks changes. The data collected through this protocol has helped with the development of new research avenues to understand, among the many alteration processes that impact paintings, the dynamics of water and fluid mechanics affecting the conservation of Cave of Altamira. These investigations help clarify how, why, and at what rate degradation processes such as pigment migration, washing, and bacterial colonization occur. The insights gained from these techniques inform indirect conservation measures aimed at reducing the deterioration of the cave art, located both on the Polychrome ceiling and throughout the rest of the Cave of Altamira. The results underline the importance of regular monitoring and the application of precise, non-invasive techniques to protect rock art from continued degradation. This research provides a model for similar conservation initiatives at other vulnerable heritage sites. Full article

The use of organic solvents, particularly those of a non-polar nature, is a common practice during cleaning operations in the restoration of polychrome artworks and metallic artifacts. However, these solvents pose significant risks to the health of operators and the environment. This study explores the formulation of innovative gels based on non-polar solvents and cellulose derivatives, proposing a safe and effective method for cleaning metallic artworks. The study is focused on a toxic apolar solvent, Ligroin, identified as one of the most widely used solvents in the cultural heritage treatments, and some “green” alternatives such as Methyl Myristate and Isopropyl Palmitate. The main challenge lies in overcoming the chemical incompatibility between non-polar solvents and polar thickening agents like cellulose ethers. To address this problem, the research was based on a hydrophilic–lipophilic balance (HLB) system and Hansen solubility parameters (HSPs) to select appropriate surfactants, ensuring the stability and effectiveness of the formulated gels. Stability, viscosity, and solvent release capacity of gels were analyzed using Static Light Multiple Scattering (Turbiscan), viscometry, and thermogravimetric analysis (TGA). The efficacy of cleaning in comparison with Ligroin liquid was evaluated on a metal specimen treated with various apolar protective coatings used commonly in the restoration of metallic artifacts, such as microcrystalline waxes (Reswax, Soter), acrylic resins (Paraloid B44), and protective varnishes (Incral, Regalrez). Multispectral analysis, digital optical microscopy, FTIR spectroscopy, and spectrocolorimetry allowed for the assessment of the gels’ ability to remove the different protective coatings, the degree of cleaning achieved, and the presence of any residues. The results obtained highlight the ability of the formulated gels to effectively remove protective coatings from metallic artifacts. Cetyl Alcohol proved to be the most versatile surfactant to realize a stable and efficient gel. The gels based on Methyl Myristate and Isopropyl Palmitate showed promising results as “green” alternatives to Ligroin, although in some cases, they exhibited less selectivity in the removal of protective coatings. Full article

This study addresses the features of the internal structure of the geological layers adjacent to the Polychrome Hall ceiling of the Cave of Altamira (Spain) and their link to the distribution of moisture and geological discontinuities mainly as fractures, joints, bedding planes and detachments, using 3D Ground Penetrating Radar (GPR) mapping. In this research, 3D GPR data were collected with 300 MHz, 800 MHz and 1.6 GHz center frequency antennas. The data recorded with these three frequency antennas were combined to further our understanding of the layout of geological discontinuities and how they link to the moisture or water inputs that infiltrate and reach the ceiling surface where the rock art of the Polychrome Hall is located. The same 1 × 1 m² area was adopted for 3D data acquisition with the three antennas, obtaining 3D isosurface (isoattribute-surface) images of internal distribution of moisture and structural features of the Polychrome Hall ceiling. The results derived from this study reveal significant insights into the overlying karst strata of Polychrome Hall, particularly the interface between the Polychrome Layer and the underlying Dolomitic Layer. The results show moisture patterns associated with geological features such as fractures, joints, detachments of strata and microcatchments, elucidating the mechanisms driving capillary rise and water infiltration coming from higher altitudes. The study primarily identifies areas of increased moisture content, correlating with earlier observations and enhancing our understanding of water infiltration patterns. This underscores the utility of 3D GPR as an essential tool for informing and putting conservation measures into practice. By delineating subsurface structures and moisture dynamics, this research contributes to a deeper analysis of the deterioration processes directly associated with the infiltration water both in this ceiling and in the rest of the Cave of Altamira, providing information to determine its future geological and hydrogeological evolution. Full article