Paint Pigments Research Articles

Archaeometric investigation of pigments of the iconostasis from Saint Georgios church of Sohos

The research presents the preliminary results of the archaeometric investigation of the painting decoration from Saint Georgios church in Sohos, Thessaloniki, Greece. The church is dated to the second half of the 18th century. At the initial stage, the study focused on the identification of the organic and inorganic pigments in the wood-carved iconostasis painting. Fifteen samples of pigments and gilding were obtained during the conservation work from (a) the semi-colonettes that separate the Despotic Icons Zone (8 samples) and (b) the bema door, the entrance to the Diakonikon (7 samples). For studying the peculiarities of the church’s decoration, optical (stereo and polarizing microscopes) and physicochemical analysis (m-XRF, FTIR, Raman, and HPLC) have been used. Most of the inorganic and organic pigments found in the decoration of the iconostasis have been used since antiquity. In general, the inorganic pigments cinnabar and minium (red lead), and the natural organic pigments cochineal and indigo were identified. The iconostasis’s overpainting pigments synthetic ultramarine, zinc white and emerald green date to the first half of the 19th century, and their production dates (c. 1800–1850) are setting a terminus post quem for the overpainting work.

Time-resolved photoluminescence imaging for the mapping of weakly luminescent pigments in paintings

Time-resolved photoluminescence imaging for the mapping of weakly luminescent pigments in paintings

Dispersion stability analysis of copper sulphide nanoparticles in different medium

Nanoparticles (NPs) of covellite CuS have been synthesised using a modified polyol method at 160ºC - 165ºC without adding any extra surfactant. These NPs were charecterized by X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive Analysis of X-ray (EDAX), Zeta potential and Dynamic Light Scattering (DLS) techniques. XRD data and three Raman modes confirm P63/mmc space group and hexagonal crystal structure of CuS NPs. EDAX data of Cu:S was slight differed from nominal 1:1 ratio due to extra S taken in synthesis. FESEM images show sheet-like NPs. The zeta potential (ξ) data analysis shows that the stability of the NPs is dependent on the dispersion medium, with high stability observed above pH 8.93 in an acidic medium. At pH 10.95, a highest ξ value of -37.64 mV is recorded in de-ionized water (DIW), while the nanoparticles are found to be unstable in ethanol and propanol as dispersion mediums. According to the hydrodynamic diameter (HD) data, the particles tend to agglomerate more quickly in ethanol and propanol compared to DIW. These findings are expected to be useful in various applications such as pigments in paints, batteries, pharmaceuticals, ceramics, and waste water treatment.

CHARACTERIZATION OF A GRECO-ROMAN STUCCO MASK (REG. NO. 229) PRESERVED AT THE NATIONAL MUSEUM OF EGYPTIAN CIVILIZATION, CAIRO, EGYPT

The Greco-Roman stucco masks are of great historical, artistic and religious importance. According to the restoration-conservation strategies, the detailed mineral characterization of artifacts is an important step that facilitates the selection of appropriate restoration procedures. Different characterization techniques such as USB digital microscope, scanning electron microscopy–energy dispersive X-ray analysis, X-ray diffraction analysis (XRD), thermal analysis (DTA/DTG), Fourier transform infrared and micro-Raman spectroscopies were used. The results indicated that gypsum is the main component of the stucco mask. As well, calcite was found as an impurity or an addition together with halite and anhydrite as deterioration products. The iron nail corrosion was the reason for a notable discoloration to the stucco mask. FTIR analysis confirms that animal glue is the adhesive material used for the reassembly of the mask. The used pigments for painting the mask are hematite for red-orange color, mixture of hematite and magnetite for brown color and mixture of gypsum and hematite for the white brown color.

Błękit i rośliny lecznicze – słów kilka o indygo i nie tylko

Blue color and medicinal plants – a few words about indigo and more Until the development of organic chemistry and the production of synthetic dyes in the second half of the 19th century, substances of natural origin were the only source of color compounds. These could be mineral, plant, and animal products, used in the form of raw products (e.g., crushed metals, minerals, animal fragments, or their excretions) and preparations derived from them. Among the plants we find many species that have been used as sources of coloring substances. They were valued primarily in the production of various utility or decorative fabrics and were used to dye natural fibers. Plant extracts or purified fractions of color compounds were also used as pigments in painting, in the illumination of books, and as substances that improve the look of medicines or foodstuffs. Some had medicinal significance per se. Among them, a small group of plant substances with a blue color is of special interest. The most famous natural raw material of this group is indigo (Indigo), obtained from Indigofera tinctoria L. and its substitutes. Noteworthy is also the less known wood of the logwood (Haematoxylum campechianum L.), known as the blue tree. This work presents the history, uses, and therapeutic importance of the abovementioned raw materials and their contemporary use.

Interpretation of the Pigments Analysis and Coloration Techniques for Ksitigarbha Bodhisattva Painting within the Myengbujeon Hall in Namwon Seonwonsa Temple, Korea

The Ksitigarbha Bodhisattva Painting of Myeongbujeon Hall in Namwon Seonwonsa temple was painted in 1917 by seven monk painters including Geumeo Manchong, Sango and Haengeun. In the painting, Korean National Flag (Taegeukgi), a trace of anti-Japanese movement that had been hidden under suppression during the invaded by the Japanese period, was found on the surface of official wooden hat in Sixth King (Byeonseongdaewang). Elements of Pb, S and Si were commonly detected by the P-XRF of the painting pigments to be analyzed, which was estimated the characteristics of the Sinamchae made by mixing colored metal oxides and glass powder, and data were secured. As the optial microscopy, scanning electron microscopy and SEM-EDS analysis show that black is chinese ink and lampblack ink, white is lead hydroxide and chalk, gold is gold foil, yellow is iron oxide yellow, massicot and gamboge, red is cinnaba, iron hydroxide and minium, green is emerald green, blue is ultramarine, respectively. As the infrared photography, various coloring techniques and traces of several overlapping for completeness were found. A comprehensive considerations of these shows that various coloring techniques with back, bottom and middle colorations were used. The Taegeuk pattern is interpreted as making a circle shape with a minium and painting with emerald green over it.

Nanoconfined Water Clusters in Zinc White Oil Paint.

Pigments in oil paint are bound by a complex oil polymer network that is prone to water-related chemical degradation. We use cryo-Fourier-transform infrared spectroscopy and differential scanning calorimetry to study how water distributes inside zinc white oil paint. By measuring water freezing and melting transitions, we show that water-saturated zinc white oil paint contains both liquid-like clustered water and nonclustered water. A comparison of titanium white paint and nonpigmented model systems indicates that water clustering happens near the pigment-polymer interface. The cluster size was estimated in the nanometer range based on the ice melting and freezing temperatures and on the position of the O-D vibration band. As liquid-like water can play a crucial role in the dissolution and transport of ions and molecules, understanding the factors that favor this phenomenon is essential for establishing safe conditions for the conservation of painted works of art.

Preliminary Diagnostic Survey of Deteriorated Paint Layers at the Maritime Station of Rocha Do Conde De Óbidos, Lisbon: A Multianalytical Research

This paper reports the preliminary diagnostic survey of the six controversial mural paintings painted in 1946–49 at the Maritime Station of Rocha do Conde de Óbidos in Lisbon, considered the artistic epitome of Almada Negreiros mural painting art. Four research questions drove this research: a) What are the main decay phenomena present and their sources? b) Which are the paint layers most affected, and are they linked to a particular pigment? c) Is there any relation between the painting technique used and the deterioration or stability of the paint layers and pigments? And finally, d) Are there differences in the decay phenomena present in both maritime stations of Alcântara? The analytical setup comprised in-situ and laboratory analysis by way of technical photography documentation (TP), handled optical microscopy (h-OM), handheld X-Ray Fluorescence (XRF), complemented by optical microscopy of microfragments and cross sections (OM-Vis-UV), X-Ray Diffraction (XRD), and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS).The first results indicate flaking of the paint layers as the main and most severe deterioration feature present in most of the murals. The yellow ochres, browns, blacks, and light greens are the colours most affected, showing different degrees of loss. The pictorial technique used, the presence and action of soluble salts in the structure, and even the products used as adhesives during past interventions might be the root of this phenomenon.

Properties and Lightfastness of Natural and Artificial Azurite Used As Painting Pigment

Azurite is an inorganic pigment commonly used in traditional painting arts and even today. This pigment has two types: natural azurite and synthetic artificial azurite, called blue verditer or blue bice. Because they have the same structure and similar appearance they are difficult to distinguish. The purpose of this study is to compare these two types pigments, focusing on material properties and accelerated weathering behavior. Natural azurite consist of copper carbonate and mineral compounds like quartz, kaolinite. On the other hand, artificial azurites are synthesized using azurite and calcite. As a result of thermal analysis, unlike natural azurite, the calcite in artificial azurite resulted in weight loss at three temperatures, at approximately 350 ℃, 650 ℃, and 840 ℃. According to the microscope analysis results, natural azurites have clearly blue angular particles with sharp edges, produced by crushing. Artificial azurite showed spherules and aggregates with tiny rounded or fibrous particles. After accelerated weathering tests, the natural azurites had no change in color, particle shape or original components, but the artificial azurites noticeably changed color and shape. The color changes of artificial azurites occurred due to the growth of calcite crystallite, a slight new product formation, and change in particle shape. Even though natural azurites are more expensive pigments, they provide superior color durability and particle shape stability compared to artificial azurites.

Understanding Frédéric Flachéron’s Paper Negative Process through Experimentation and Specular Reflection FTIR Analysis

Cultural heritage objects present a special set of challenges for chemical analysis. Often micro-sampling or even contacting the object is deemed an unacceptable risk to the object. This study examined if specular reflection FTIR, a non-sampling and non-contact analytical technique, can provide insight into chemical composition of the layered coatings on Frédéric Flachéron’s paper negatives (1848–1852) in the Harrison D. Horblit Collection of Early Photography, in Houghton Library, at Harvard University. Specular reflection FTIR data confirmed the identification of beeswax and sandarac as the transparentizing media on Flachéron’s paper negatives, as previously published by Lee Ann Daffner. However, specular reflection FTIR analysis also indicated that some negatives had additional localized coatings of orange shellac in specific areas of the images. To understand why Flachéron retouched his negatives with orange shellac, modern experimental replications of the paper negative process were performed. Through modern experimentation with the paper negative technique, it was found that Flachéron’s coatings of shellac served as an integral part of his image-altering technique. The color of the orange shellac subtly alters contrast and density, but it does not mask an area the way an opaque watercolor or highly pigmented paint might. The fine adjustments to the negatives with orange shellac were an attempt to perfect the contrast in the print, and better render depth and detail. These discoveries add to a growing body of recent research that points to the historic and art historic importance of negatives and coatings in photography. The specificity with which specular reflection FTIR was able to nondestructively identify the chemical composition of the local coating, and specifically target the analysis on the areas in which it appeared, allowed for an understanding of Flachéron’s use of local coatings as a retouching method rather than a protective coating.

Synthesis of a europium complex with ultrahigh quantum yield and its application as an invisible luminescent additive in pigments for preservation of cultural relics

A europium coordination compound [Eu2(ppip)2(PhCOO)6] (ppip is 1,2-diphenylimidazo[4,5-f][1,10]phenanthroline) has been synthesized and structurally characterized. In this symmetric dinuclear complex of octa-coordinated Eu(III) atom, both hanging phenyl rings in the ppip are twisted dramatically from the imidazophenanthroline part, leading to strong edge-to-face (T-type) C–H∙∙∙π interaction. This pale yellow stable complex possesses an ultrahigh luminescence quantum yield (84.2 ± 0.2%) under excitation at 365 nm, and hence is explored to be utilized in the preservation pigments for traditional Chinese paintings as an luminescent additive, which looks invisible under normal light, but exhibits bright red luminescence under UV excitation at a rather low percentage (0.02% wt).

Comparison of macro x‐ray fluorescence and reflectance imaging spectroscopy for the semi‐quantitative analysis of pigments in easel paintings: A study on lead white and blue verditer

AbstractMacroscopic x‐ray fluorescence imaging spectroscopy (MA‐XRF) and reflectance imaging spectroscopy (RIS) are important tools in the analysis of cultural heritage objects, both for conservation and art historical research purposes. The elemental and molecular distributions provided by MA‐XRF and RIS respectively, are particularly useful for the identification and mapping of pigments in easel paintings. While MA‐XRF has relatively established data processing methods based on modeling of the underlying physics, RIS data cannot be modeled with sufficient precision and its processing has considerable room for improvements. This work seeks to improve RIS data processing workflows in the short wavelength infrared range (SWIR, 1000–2500 nm) with a novel method that fits Gaussian profiles to pigment‐specific absorption features, and we compare its performance to MA‐XRF for the task of semi‐quantitative pigment mapping, evaluating their limits of detection (LODs) and the matrix effects that affect their signals. Two pigments are considered in this work, lead white and blue verditer, which are mapped in SWIR RIS using the first overtone of OH stretching of their primary compounds, hydrocerussite (Pb3(CO3)2(OH)2) and azurite (Cu3(CO3)2(OH)2), at 1447 and 1497 nm respectively, and in MA‐XRF using the Pb‐L and Cu‐K fluorescence signals. The methods are evaluated using two sets of custom‐prepared paint samples, as well as a 16th‐century painting, discussing the identification, mapping, and semi‐quantitative analysis of the considered pigments. We found SWIR RIS to be a pigment‐specific method with a longer linear range but inferior LODs and penetration depth when compared to MA‐XRF, the latter is often not capable of discriminating between different pigments with identical elemental markers. We furthermore present a novel color scale that allows the simultaneous visualization of signals above and below a confidence limit.

Kapadokya’daki Post-Bizans (XIX yüzyıl) Kilisesindeki Duvar Resimlerindeki Pigmentlerin Arkeometrik Teknikler ile Araştırılması

Cappadocia region, rock churches, monasteries, houses, underground settlements, valleys and historical and geological formations have unique beauty. The region, which is rich with its cultural assets belongs to Christian culture in Anatolia, is generally known with its rock churches, and is a subject to researches. The purpose of this study is; to understand the wall painting technology of the 19th century church, and to make a comparison with the wall painting materials of the rock churches. The study material is composed of pigments in the wall paintings of the Church of St. Theodoros Trion, which is from the 19th century, and located in Nevşehir. Scanning Electron Microscope and Energy Distributed Spectrometer (SEM-EDX), X-Ray Diffraction Spectrometry (XRD) and Fourier Transformed Infrared Spectrophotometer (FTIR) are used to determine material characterization of pigments. X-Ray Fluorescence Spectrometer (XRF) analysis method was used in the analysis of the soil structure. As a result of analysis of the wall painting, it has been found that the ultramarine pigment is obtained from the lapis lazuli mineral and the covellite mineral of the covellite blue. In red, the red ochre and the caput mortuum pigment in purple color has been found. In the mineral of different pigment species, bauxite mineral belongs to the region have been detected. Green color, it has been determined that it is obtained from the glauconite and celadonite mineral in the region. According to the research carried out in the region in green color, it has been detected that only this pigment species has been used from the 6th century to the 19th century.

Seeing in the dark: Challenges in the interpretation of x‐ray fluorescence element distribution maps associated with black paints

AbstractDuring the conservation of easel paintings, black draperies or dark backgrounds often prove problematic to treat and understand in terms of condition. Despite most black pigments in Old Master paintings not intrinsically containing high atomic number elements, the investigation of black paints is one of the National Gallery's major uses and most helpful applications of x‐ray fluorescence (XRF) scanning. As a visual tool, XRF element distribution maps of black paints are useful for assessing the extent of overpainting or condition of any surviving original paint beneath, and for revealing the original modelling. However, interpreting the XRF element maps can be challenging. It is important to consider not only the primary compositions of black or dark pigments, but to have an understanding of other possible associated materials and more broadly of historical painting techniques, artists' practices and the paint stratigraphy. Through a series of case studies, this paper demonstrates how a detailed knowledge of historic painting materials and techniques, based on study of documentary sources and archives of materials‐based evidence from the analysis of paint cross‐sections—both from the paintings being studied and related works—aids and enriches interpretation of XRF element maps of black paints. While samples are invaluable in understanding exactly how—and with what materials—such regions were painted, they are not always representative and scanning XRF may be of complementary benefit in providing a more holistic view of pigment distribution. The examples presented range from the fifteenth to the seventeenth century from both Northern Europe and Italy.

Raman spectroscopy of yellow organic pigments of large Korean Buddhist paintings from the late Joseon dynasty (17th–19th centuries)

AbstractThe yellow coloring of the organic and inorganic pigments used in large Buddhist paintings during the late Joseon dynasty (17th–19th centuries) is herein analyzed using Raman spectroscopy and non‐invasive component analysis via p‐XRF. p‐XRF analyses of 194 yellow points on 12 large Buddhist paintings confirmed the use of gold, orpiment, and organic pigments; however, the yellow chromophoric elements of the organic pigments were not detected. The confirmed colors ranged from light yellow (close to white) to bright and dark yellow, but microscopic analysis revealed no particles or crystals. Accurate identification of pigments comprising light elements or organic compounds is challenging, which limits their identification via p‐XRF. In contrast, Raman spectroscopy of the samples presumed to be organic pigments detected gamboge in the samples, either alone, mixed with a white inorganic pigment such as lead white to express yellow, or overlaid upon such a pigment. These results demonstrate the utility of Raman spectroscopy in the analysis of organic pigments and provide a guide for the identification of coloring materials used in cultural heritage artifacts.

Characterization of calcined red soil applied in the removal of methylene blue dye from wastewater to produce a hybrid pigment

AbstractWe obtained natural red soil (RS), rich in iron, from the region of Palotina in the state of Paraná, Brazil. The RS sample was purified by suspension in water and sieved to remove plant particulates. It was then treated thermally at 800°C to remove organic volatiles; this sample was called RS800. The samples were characterized using X-ray diffraction, X-ray fluorescence, infrared and electronic spectroscopy, ζ-potential analysis and scanning electron microscopy. Colorimetric studies were performed according to the CIEL*a*b* system. Tests have shown that RS800 has the ability to remove methylene blue (MB) dye from wastewater. Thus, it was used as an adsorbent at various temperatures (25, 35, 45°C). According to the Langmuir model, the maximum adsorption capacity (qmax) was 23.256 mg g–1 (25°C). Unexpectedly, increasing temperature reduced qmax to 21.659 mg g–1 at 35°C and to 21.186 mg g–1 at 45°C. Therefore, RS800 must be used at room temperature (25°C), making its application in large-scale wastewater treatment feasible. After using RS800 as an adsorbent, the solids were filtered, dried, pulverized, and used as hybrid pigments in commercial white paints. Pigmented paints were used to paint a plaster specimen and colorimetric measurement was performed. These paints were tested for colour stability in acidic and alkaline environments. The results indicate that RS800 is efficient in the treatment of water contaminated with cationic dyes and can be reused as a hybrid pigment.

Non-invasive study of the dyes and pigments in the Chinese woodblock New Year paintings

Woodblock New Year painting is a traditional Chinese folk art that flourished during the 19th and early 20th centuries. These paintings feature a wide variety of colors, particularly after the introduction of synthetic colorants from Europe in the late 19th century. The scientific identification of dyes and pigments used in these paintings can provide valuable insights into the socio-historical context of the time. However, the history of materials used in the printing of New Year paintings is still lacking adequate information. In this study, we employed a combination of spectroscopic and imaging techniques, including Macro X-ray fluorescence imaging (MA-XRF), hyperspectral imaging, and Raman spectroscopy to identify the dyes and pigments used in two Yangliuqing New Year paintings. Our analysis revealed the presence of both traditional pigments and synthetic colorants, such as vermilion, Prussian blue, and methyl/crystal violet. We also discovered several color-matching techniques used to create light pink, light orange, and dark purple hues. These findings suggest that synthetic colorants were gradually replacing traditional pigments in China due to the growth of global trade at that time. Furthermore, our research provides valuable information for the conservation, preservation, and display of New Year paintings.

High NIR Reflectance and Photocatalytic Ceramic Pigments Based on M-Doped Clinobisvanite BiVO4 (M = Ca, Cr) from Gels.

Clinobisvanite (monoclinic scheelite BiVO4, S.G.I2/b) has garnered interest as a wide-band semiconductor with photocatalyst activity, as a high NIR reflectance material for camouflage and cool pigments and as a photoanode for PEC application from seawater. BiVO4 exists in four polymorphs: orthorhombic, zircon-tetragonal, monoclinic, and scheelite-tetragonal structures. In these crystal structures, V is coordinated by four O atoms in tetrahedral coordination and each Bi is coordinated to eight O atoms from eight different VO4 tetrahedral units. The synthesis and characterization of doped bismuth vanadate with Ca and Cr are studied using gel methods (coprecipitated and citrate metal-organic gels), which are compared with the ceramic route by means of the UV-vis-NIR spectroscopy of diffuse reflectance studies, band gap measurement, photocatalytic activity on Orange II and its relation with the chemical crystallography analyzed by the XRD, SEM-EDX and TEM-SAD techniques. The preparation of bismuth vanadate-based materials doped with calcium or chromium with various functionalities is addressed (a) as pigments for paints and for glazes in the chrome samples, with a color gradation from turquoise to black, depending on whether the synthesis is by the conventional ceramic route or by means of citrate gels, respectively; (b) with high NIR reflectance values that make them suitable as fresh pigments, to refresh the walls or roofs of buildings colored with them; and (c) with photocatalytic activity.

Study on the Influence of Electron Beam Radiation Sterilization Method on Chinese Mural Pigment

Murals are one of the important cultural heritages of mankind. The microbial control of murals is an important subject in mural painting conservation. In recent years, electron beam radiation sterilization has attracted more and more attention in the field of cultural relic protection. Murals are immovable cultural relics, so conventional electron beam irradiation equipment can not be used. However, the development of small mobile electron beam irradiation equipment shows the potential of radiation’s application in the sterilization protection of immovable cultural relics such as murals. A feasibility study of radiation sterilization in mural paintings is needed to investigate the effect of sterilization and the influence of sterilization dose on the stability of mural painting pigments and bonding materials. In this paper, the radiation effects of typical bacteria in tomb murals and mineral pigment powder in ancient Chinese paintings were studied in a laboratory. Firstly, aeromonas hydrophila (Aer.h) and penicillium flavigenum (PNC) were selected as representative strains to determine the appropriate sterilization dose for murals. Then, the effects of radiation on seven kinds of ancient Chinese mineral pigments and white calcium carbonate in the ground layer were verified. The results are as follows: the radiation dose of 10 kGy can effectively remove the two typical strains. This sterilization dose will cause a color difference in calcium carbonate and lead white, while other color pigments are essentially stable. Based on the color difference and UV-vis intensities of the four white carbonate samples, the color change in two of them increased with increasing the dose up to 30 kGy, after which signs of saturation began to appear. X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectra showed that the chemical structure of the samples did not change after irradiation. The formation of free radicals in treated samples was confirmed using an electron paramagnetic resonance (EPR) spectrum test. According to all characterization results, the color difference between the four white carbonate samples may be due to the combination of unpaired electrons and defects in the process of electron beam irradiation to form color centers. After forming the color center, the light absorption of the four samples changed. This is a reversible change, but the samples will take a long time to return to their original state. This study focuses on the influence of electron beam radiation on pigment composition, which is a preliminary exploration of whether radiation sterilization can be applied to the protection of ancient Chinese mural paintings, and the experimental results can provide basic data for later application.

Mixed oxides with corundum-type structure obtained from recycling can seals as paint pigments: color stability.

Green chromium and red iron oxides are technically important pigments due to their high color intensity, good dispersibility in paints, and superior hiding power. We report on the synthesis of colored pigments of mixed oxides with a corundum-type structure. The pigments are obtained via the addition of coloring ions to boehmite from recycled metallic aluminium. X-ray diffractometry (XRD) and Raman spectroscopy confirmed the crystallographic phase. Additionally, the oxidation state 3+ responsible for the greenish (chromium) and reddish (iron) coloration of the mixed oxides was confirmed by XPS and visible-light absorption measurements. The colorimetric stability of the oxides in acid and alkaline environments was evaluated. After 240 h of exposure to harsh environments, both pigments demonstrated stability and showed no strong color difference.