Pigment Mixtures Research Articles

Correction: Nanoporous Film Layers to Enhance the Performance of Passive Radiative Cooling Paint Mixtures

Correction: Nanoporous Film Layers to Enhance the Performance of Passive Radiative Cooling Paint Mixtures

Spectral absorbance changes in the photoreceptors of the juvenile masked greenling, Hexagrammos octogrammus (Pisces, Hexagrammidae).

When changing habitat during migration or ontogenesis, fish encounter changes of the visual environment, among which the most important is the spectral composition of light and turbidity. This leads to changes in the behavior, morphology, and physiology of the visual system, in particular, spectral sensitivity, which is determined by the properties of visual pigments. The masked greenling Hexagrammos octogrammus has an additional factor that shapes effective spectral sensitivity-the presence of densely bright orange cornea which reversibly changes its density depending on the state of light/dark adaptation. However, it is unknown to what extent the properties of visual pigments are matched to spectral properties of the developing cornea at the final stage of metamorphosis during migration of juveniles from pelagic to coastal environments. The findings of this microspectrophotometric study show that the range of the spectral sensitivity of rods and cones in juveniles is much wider than in adults, with a shift in the sensitivity of a significant part of the cells to shorter wavelengths. The reason for this is the large variation in the ratio of chromophores A1:A2 in the pigment mixture in each cell and possible expression of new opsins. This also indicates the asynchrony of pigment transformations in different types of photoreceptors and the incompleteness of these transformations on the eve of the transition to bottom life in shallow water.

Effect of Plasma Treatment on Self-Cleaning Features of Acrylic Paint/TiO2-Coated Surfaces for Environmental Pollutant Removal

This study investigates the characterization and performance of self-cleaning TiO2 surfaces synthesized through a one-step preparation process, followed by enhancement via plasma treatment. The process involved coating aluminum foil with an acrylic paint mixture containing nanoparticles of different mass compositions and subsequent plasma treatment using a continuous plasma arc. Scanning electron microscopy revealed the morphology of the treated surfaces, showing an increase in surface area of plasma-treated materials. Energy-dispersive X-ray spectroscopy revealed changes in oxygen and titanium in acrylic paint/TiO2 surfaces as the TiO2 content increased, indicating successful TiO2 incorporation. Raman spectroscopy showed that the bulk structure of self-cleaning acrylic paints is mainly preserved after plasma treatment. Alternating current impedance spectroscopy assessed that plasma treatment reduced agglomeration and increased active sites, especially for the acrylic paint/TiO2 surfaces with 0.5 mg/cm3 TiO2. The contact angle measurements indicated that plasma treatment enhanced the superhydrophobic characteristics and potential self-cleaning abilities of produced acrylic paint/TiO2 surfaces. The efficacy of these plasma-treated surfaces in self-cleaning was evaluated by testing their performance against puddle sediment and automotive oil samples. The study demonstrated that plasma treatment positively impacted the self-cleaning ability of the acrylic paint/TiO2 surfaces, particularly those with 0.5 mg/cm3 TiO2. This enhancement was attributed to the formation of functional groups, improved water repellency, and possible increases in surface area, which collectively contribute to the sustainable self-cleaning properties of the treated surfaces.

Nanoporous Film Layers to Enhance the Performance of Passive Radiative Cooling Paint Mixtures

Nanoporous Film Layers to Enhance the Performance of Passive Radiative Cooling Paint Mixtures

Exploring Carolingian and Romanesque cycles: a study of the detached wall paintings from the Church of St. Johann in Müstair

Twenty-six fragment of wall paintings detached from the upper register of the Carolingian and Romanesque cycles of the church of St. John in Müstair (Switzerland) have been part of the Swiss National Museum collection since the beginning of the twentieth century. As some of these objects were in a critical state of conservation, a research project was launched to assess and document their conditions, and to gain knowledge about painting materials and execution techniques, in view of planning a conservation project. In a first phase, non-destructive analyses were carried out, using handheld XRF and portable FTIR spectroscopy; followed by the targeted collection of samples for detailed analysis in the laboratory. In parallel, similar investigations were carried out on the imprints left on the walls of the church’s attic. The results allowed the identification of the pigment palette and the execution technique. Besides earth pigments such as ochres, a lime-based white, probably bianco di San Giovanni, and limited amounts of lapis lazuli were used in both painting cycles. For the Carolingian cycle, Egyptian blue and mixtures of several lead-based pigments were also identified. In several instances, the deterioration of lead-based pigments resulted in shades of grey to black severely modifying the original appearance of the wall paintings. Additionally, both cycles have suffered from pigment alteration due to fire. The obtained results, together with iconographic considerations, allowed for an extended interpretation of possible original colour palette.Graphical

Development of cellulose acetate poly acrylonitrile (CAPA)–SiC/epoxy coating to mitigate corrosion of copper in chloride containing solutions

A new conducting polymer of the cellulose acetate poly acrylonitrile (CAPA)–SiC composite was produced using an in situ oxidative polymerization technique in an aqueous medium. SiC was synthesized from Cinachyrella sp. as a source of carbon and silicon at 1200 °C under an argon atmosphere via a catalytic reduction process. The structure and morphology of the CAPA–SiC composite were characterized using surface area studies (BET), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), and surface morphology (SEM & TEM). To protect copper, the produced CAPA–SiC composite was mixed with commercial epoxy paint using a casting technique, and the copper surface was coated with the three components of the CAPA–SiC/epoxy paint mixture. The corrosion inhibition improvement of the CAPA–SiC/paint coating was assessed using electrochemical impedance spectroscopy followed by Tafel polarization measurements in a 3.5 wt% NaCl solution. The corrosion protection ability of the CAPA–SiC/epoxy coating was found to be outstanding at 97.4% when compared to that of a CAPA/paint coating. SEM and XRD were used to illustrate the coating on the copper surface.

Advances in Automated Pigment Mapping for 15th-Century Manuscript Illuminations Using 1-D Convolutional Neural Networks and Hyperspectral Reflectance Image Cubes

Reflectance imaging spectroscopy (RIS) is invaluable in mapping and identifying artists’ materials in paintings. The analysis of the RIS image cube first involves classifying the cube into spatial regions, each having a unique reflectance spectrum (endmember). Second, endmember spectra are analyzed for spectral features useful to identify the pigments present to create labeled classes. The analysis process for paintings remains semi-automated because of the complex diffuse reflectance spectra due to the use of intimate pigment mixtures and optically thin paint layers by the artist. As a result, even when a group of related paintings are analyzed, each RIS cube is analyzed individually, which is time consuming. There is a need for new approaches to more efficiently analyze RIS cubes of related paintings to address the growing interest in the study of related paintings within a group of artists or artistic schools. This work builds upon prior investigations of 1-D spectral convolutional neural networks (CNNs) to address this need in two ways. First, an expanded training set was used—ten illuminated manuscripts created by artists stylistically grouped under the notname “Master of the Cypresses” (15th century Seville, Spain). Second, two 1-D CNN models were trained from the RIS cubes: reflectance and the first derivative. The results showed that the first derivative-trained CNN generally performed better than the reflectance-trained CNN in creating accurate labeled material maps for these illuminated manuscripts.

Discovery of pararealgar and semi-amorphous pararealgar in Rembrandt's The Night Watch: analytical study and historical contextualization

This article reports on the discovery of pararealgar and semi-amorphous pararealgar in Rembrandt's masterpiece The Night Watch. A large-scale research project named Operation Night Watch was started in 2019. A variety of non-invasive analytical imaging techniques, together with paint sample research, has provided new information about Rembrandt's pigments, materials, and techniques as well as the current condition of the painting. Macroscopic X-ray fluorescence, macroscopic X-ray powder diffraction and reflectance imaging spectroscopy identified the presence of arsenic sulfide pigments and degradation products of these pigments in the doublet sleeves and embroidered buff coat worn by Lieutenant Willem van Ruytenburch (central figure to the right of Captain Frans Banninck Cocq). Examination by light microscopy of two paint samples taken from this area shows a mixture of large sharp-edged tabular yellow and orange to red pigment particles, and scanning electron microscopy-energy dispersive X-ray analysis identified these particles as containing arsenic and sulfur. Using micro-Raman spectroscopy, the yellow particles were identified as pararealgar, and the orange to red particles as semi-amorphous pararealgar. Synchrotron-based X-ray diffraction allowed visualization of the presence of multiple degradation products associated with arsenic sulfides throughout the paint layer. The discovery of pararealgar and semi-amorphous pararealgar is a new addition to Rembrandt's pigment palette. To contextualize our findings and to hypothesize why, how, and where Rembrandt obtained the pigments, we studied related historical sources. A comprehensive review of historical sources gives insight into the types of artificial arsenic sulfides that were available and suggests that a broader range of arsenic pigments could have been available in Amsterdam in the seventeenth century than previously thought. This is supported by the use of a very similar mixture of pigments by Willem Kalf (1619–1693), a contemporary artist based in Amsterdam. Together with the condition of the particles in the paint cross sections, this brings us to the conclusion that Rembrandt intentionally used pararealgar and semi-amorphous pararealgar, together with lead–tin yellow and vermilion, to create an orange paint.

Uso da análise de variância e do teste de Tukey para comparar quatro marcas de tintas industriais

Objective: The aim of this paper is to show the application of Analysis of Variance and Tukey's Test to compare four brands of paint used in a company's production. Theoretical framework: Analysis of Variance, or ANOVA, is a statistical method used to determine whether there are significant differences between the means of three or more independent groups. This technique was developed by the British statistician and geneticist Ronald Fisher at the beginning of the 20th century (Bosco v & Bispo, 2010). Method: Data was taken from a company in the South of Rio de Janeiro and a case study was carried out using Analysis of Variance and Tukey's test. Final Considerations: This result indicates that the hardness of the paint mixtures differs significantly. Some of the group averages are known to be different. Tukey's comparison results were used to formally test whether the difference between a pair of groups is statistically significant. It was found that Paint 4 has a higher hardness than the others. Implications of the research: The use cases of Analysis of Variance and Tukey's Test are multiplying in the scientific literature and are proving to be highly effective for processing data in a wide variety of areas. Originality/value: Despite being well-known statistical tools, Analysis of Variance and Tukey's Tests are only valid in cases where there are more than two types of samples in which the statistical assumptions have been confirmed.

Analysis of Post-Treated Paint Production Waste Water at Global Company, Namanve Industrial Area

Paint is a liquid mixture of pigments, binders, solvents, and additives used for decorative, protective, and functional purposes. It forms a solid film upon drying or curing, providing color, protection against corrosion, and enhancing the aesthetic appeal of structures. However, paint manufacturing plants produce waste with high concentrations of ions, organic debris, high Chemical Oxygen Demand (COD), biological oxygen demand, turbidity, suspended solids, and heavy metals, which are harmful to the environment. Wastewater is a significant challenge for urban authorities and industries today. The study highlights the estimation of wastewater generated and the pollutants arrangement adopted by city authorities, suggesting long-term recommendations for proper waste management in Kampala. The majority of water used in paint production comes from municipal public supply, followed by well and surface water sources. Around 70% of the total water is discharged untreated, with 25% not discharged but disposed off by evaporation or other methods. Most of the water generated in paint production comes from cleaning equipment used in water-based paint production, which contains high levels of pollutants that pose significant environmental risks when inadequately treated. Keywords: Paint production, Wastewater, Global company, Namanve Industrial Area, Environmental risks

The Application of Cathodoluminescence (CL) for the Characterization of Blue Pigments

The combined application of Cathodoluminescence (CL) with Scanning Electron Microscopy (SEM) on paintings and painted surfaces has the potential to identify both organic and inorganic pigments on a micrometre or even nanometre scale. Additionally, the combination with Energy-Dispersive Spectrometry (EDS) allows for a more holistic, elemental, and mineralogical characterization of pigments. In addressing the need for the creation of a robust, open access database of characteristic CL spectra of pigments, a large project has been undertaken, focusing primarily on common organic and inorganic pigments. The present paper focuses on the CL characterization of 10 significant blue pigments in pure powder form: cerulean blue, Egyptian blue, Han blue, indigo, lapis lazuli, Maya blue, phthalo blue, vivianite, ultramarine blue, and zirconium blue. The CL spectra present characteristic bands for most of the pigments, allowing their secure identification, especially when combining the results with the EDS analyses. The effect of binding media and of the mixture of different pigments was also studied, via the analysis of mixtures of pigments with oil painted over canvas. Overall, both the binding medium and the mixture of pigments do not appear to create significant differences in the occurring spectra, thus allowing the identification of individual pigments. EDS and RAMAN spectra are included in order to facilitate comparison with other databases.

A Characterisation of the Protrusions on Liu Kang’s Boat scene (1974) from the National Gallery Singapore

This paper investigates the oil on canvas painting Boat scene (1974) by Liu Kang (1911–2004), belonging to the National Gallery Singapore (NGS). The focus is on disfiguring paint protrusions in a specific area and colour in the composition. Moreover, in search of the possible factors responsible for the creation of the protrusions, the structure and composition of the paint layers were determined. Three possible reasons were put forward to explain this phenomenon: deliberate textural effects, the expansion of metal soaps and unintentional paint contamination during the artistic process. Investigative techniques such as technical photography, digital microscopy, optical microscopy (OM), polarised light microscopy (PLM), field emission scanning electron microscope (FE-SEM-EDS) and attenuated total reflectance micro-Fourier transform infrared spectroscopy (ATR μ-FTIR) were employed to analyse paint layers, including protrusion samples. The analyses revealed that the protrusions resulted from an unintentional contamination of the oil paint during the artistic process by dry fragments of different pigment mixtures bound in drying oil. Zinc soaps were found in significant concentrations within the protrusions and other parts of the painted scene. Nevertheless, the metal soaps do not pose a direct risk to the integrity of the paint layers at the time of this research. The analyses highlight the potential challenges caused by the protrusions that conservators may face while caring for the painting. The research contributes to our ongoing comprehension of the artist’s working process.

X-ray fluorescence analysis in the study of paintings – an overview

Energy dispersive X-ray fluorescence analysis (EDXRF) is an excellent method in investigations of cultural heritage treasures, including easel and wall paintings and illuminations in ancient manuscripts. As one of the few methods applicable for this purpose, it is non-destructive and non-invasive. It is often combined with other methods such as optical microscopy, visible light photography, UV fluorescence photography, infrared reflectography, Fourier transform infrared spectroscopy, X-ray radiography, Raman spectrometry and others. The complex layered structure and mixtures of pigments, especially on easel paintings, represent a challenging task from the point of view of analysis. However, without taking samples it is only possible to analyse the thin surface layer of the investigated object with a thickness of tens to a few hundreds of micrometres. Nevertheless, this is not too much a problem when analysing paintings and even more so in the analysis of illuminations in manuscripts. The paper has an overview character and aims to summarise the possibilities, advantages and problems of XRF in this area and to demonstrate them on selected examples of published works, which in some cases are devoted to the works of leading painters from various historical periods (Giotto di Bondone, Antonello da Messina, Raffaelo Sanzio, Antonio Allegri da Corregio, Anthonis van Dyck, Rembrandt van Rijn, Giorgio Marini, Pablo Picasso and others). This review includes also a brief mention of selected research carried out in our laboratory.

Pemanfaatan Serbuk Kaca Sebagai Peningkatan Waterproofing pada Bahan Tambah Cat

In the construction of a project, walls account for approximately 20% - 40% of the total budget. Wall works are considered costly as they involve various tasks such as brick installation, plastering, rendering, and painting. Nowadays, the use of paint is widespread in line with the development of construction projects in Indonesia. Paint utilization has been extensively developed with various innovations, one of which is waterproofing paint that can protect surfaces from water or moisture. By adding a special ingredient to the paint to enhance its waterproofing properties, wall paint becomes more resistant to rain exposure over time. Therefore, the addition of glass powder to the paint mixture is needed to increase the waterproofing level because glass powder has nonporous characteristics, meaning it does not easily absorb or retain water. The objective of this research is to determine the water resistance of paint with the addition of glass powder at levels of 0%, 2,5%, 5%, 7,5%, and 10% in each 1 kg paint sample. The most optimum paint formulation is achieved by adding a 10% glass powder content, resulting in water leakage test of 0 mL, adhesion test of 5A, water absorption of 6.587%, specific gravity of 2.092 g/mL, coverage of 5.553 m²/Kg, and drying time of 4 minutes. This study aims to contribute to the development of high waterproofing wall paint that is also environmentally friendly.

Anti-corrosion resistance of coatings based on powder epoxy paints containing modifiers

The corrosion resistance of coatings (thickness 70 µm) based on epoxy powder paints modified with aliphatic amine or a mixture of anticorrosive pigments to the action of sodium chloride solution and salt spray has been studied. It is showed that with the increase of molecuar weight of initial epoxy oligomer and also at the incorporation of chemisorbing alifatic amine, containing polar groups, to the decrease in the permeability of the sodium chloride solution into the coating material is observed. It has been established that the observed changes in the properties of the coatings are due to the formation of a spatial structure of the polymer with different cross-link frequencies. It is shown that the introduction of a mixture of anti-corrosion pigments into the composition of paints provides a significant increase in the protective properties of coatings and a high preservation of the physical and mechanical properties of coatings in comparison with the base compositions. For 9000 hours of testing in a sodium chloride solution, the strength characteristics of the coatings decrease by about 10–12 % from the original ones. Based on the results of tests of coatings to the action of salt spray, the possibility of using the developed epoxy powder paints for operation in environments of a high atmospheric-corrosive category – C 5–1, including the application of coatings directly on a metal surface (Direct to metal) without multi-stage preparation of the metal surface for painting, is shown.

Spectral Mapping Techniques for the Stratigraphic and Compositional Characterisation of a 16th-Century Painting

Identifying a painting’s pigment palette is crucial for comprehending the author’s technique, as well as for evaluating the degradation of the materials. This paper investigates the stratigraphy and pigments distribution of a 16th-century painting from the Uffizi Galleries collection. Firstly, we obtained compositional information through the cross-sectional analysis of samples using scanning electron microscopy. Secondly, we performed elemental mapping using macro-X-ray fluorescence followed by reflectance imaging spectroscopy. The painting image cube was analysed using the spectral correlation mapping (SCM) classification algorithm to accurately identify the distribution and composition of the pigment mixtures.

A novel methodology for designing Mono/Bi-slab X-band microwave absorbers of Carbon-Powder composites

This work introduces a methodology for the design of X-band microwave absorbers using carbon-graphite powder composites. The reflection loss (RL) is adjusted through variations in sample thickness, mono/bi-slab geometries, and effective dielectric constant. The impact of the particle size of the powders and the volume fraction (v.f.) of the composites on the effective dielectric permittivity has been systematically investigated. The Nicolson-Ross-Weir (NRW) conversion and the Birchak dielectric mixing model were employed. Optimal absorption conditions predicted by RL simulations were validated through experimental waveguide measurements for mono/bi-slab systems of paraffin-carbon composite samples. The mono-slabs with a particle size of 3.5 μm showed the best versatility for tailoring the RL in the X-band through v.f. variations while maintaining a fixed thickness of 2 mm. In addition, a bi-slab system (powder-paraffin/paraffin) for such powder size, at 18.0 % of v.f., showed an enhanced RL with a bandwidth of 2.6 GHz and a minimum of − 40 dB (at 11 GHz). Other dielectrics based on resin:paint mixtures were tested to replace the paraffin-matrix, revealing a strong powder-matrix interaction capable of modulating the effective dielectric permittivity. Finally, experimental antenna RL measurements conducted in free space were corroborated by theoretical simulations based on the waveguide characterizations.

Surface roughness of pigmented and non-pigmented maxillofacial silicone elastomer before and after artificial aging

Maxillofacial prostheses are frequently made from silicone elastomer. The silicone material’s rough surface can lead to the accumulation of microorganisms, irritation of the surrounding soft tissue, and the progression of some microsites into mechanical failure and color deterioration. This in vitro study aimed to compare the surface roughness of M511 heat-vulcanized maxillofacial silicone before and after artificial aging. Eighty disk-shaped specimens were prepared and divided equally among five experimental groups based on pigmentation, with 16 samples in each group. The colorless specimens were prepared without adding any pigment. The four study groups were prepared using distinct pigments (red, blue, yellow, and their mixture). Half of the specimens in each group were tested before aging, while the other half was tested after 750 h of artificial aging. Surface roughness was measured using atomic force microscopy (AFM), and the silicone bonds and pigments were observed using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Data were compared between groups using a two-way analysis of variance, independent sample t-test, and Tukey’s post hoc test, considering a p < 0.05 statistically significant. FTIR-ATR showed no differences between the pre-and post-aging groups, with similar peaks observed. The surface roughness significantly increased in the colorless, blue, and mixed pigment groups (p < 0.001), surface roughness increased by 155.66%, 14.83%, and 96.12% respectively for colorless, blue pigment, and the mixture of pigments after 750 h of artificial aging. In contrast, the surface roughness significantly decreased in the yellow pigment (90.98%) and red pigment (5.7%) (p ≤ 0.001) after aging. The yellow pigment showed the smoothest surface after aging, while colorless specimens showed the roughest surface. Two-way ANOVA showed that pigment type and aging time significantly affected surface roughness. Therefore, induced aging considerably impacted the surface topography of maxillofacial silicone. The pigment type and distribution in the silicone matrix affected its surface roughness. The AFM analysis is a simple and straightforward method for assessing surface roughness at the nanometer level.

The first identification of composite paints with proteinaceous binder in Upper Palaeolithic (31–23 ka) organic decorations

Research of coloring pigments and binding compounds from the Upper Palaeolithic (UP), including on portable art objects such as personal ornaments, provides new insights into social and cultural aspects of human history. However, we lack a comprehensive study of the composite pigment mixtures and binding materials that were produced intentionally and used for coloration. The study of several personal ornaments from the UP layers dated 31–23 ka calBP in Mezmaiskaya Cave, North Caucasus (Russia), shows that UP paints have a complex chemical composition. Using ATR–FTIR and SEM–EDS, we have identified that for coloring organic personal decorations UP humans used composite paint mixtures produced from organic (bitumen) and inorganic (red bolus/kaolin) natural pigments. Also, we firstly identified that UP humans applied a proteinaceous binder, likely representing a kind of the gelatine type animal glue, which they intentionally produced from animal origin materials using boiling. This is the oldest evidence of boiling placing its origin at about 30 ka within the late UP and linking this innovation to the need of producing organic binding material for dyeing rather than with the food preparation.

Enhancing solar still thermal performance: The role of surface coating and thermal energy storage in repurposed soda cans

Despite technical developments, fresh water remains a critical human need unmet in many distant regions. This research investigates a solution by enhancing a single slope solar still (SSSS) with paraffin wax as an energy storage medium in recycled soda cans. These cans were coated with a unique mixture of black paint and carbon soot nanoparticles gathered from automobile engine exhausts to boost thermal conductivity and heat absorption. These nanoparticles, averaging 50–60 nm in size, greatly enhanced the heat absorption efficiency of the cans. Morphological examination demonstrated a consistent distribution of nanoparticles across the surfaces of the cans. The experimental setup was kept at a constant water depth in three different configurations: SSSS without phase change material (PCM) cans, SSSS with uncoated PCM cans, and SSSS with coated PCM cans. The SSSS with coated PCM cans showed significant improvements in thermal performance and cumulative yield, with gains of around 75.7 % and 102.3 %, respectively, when compared to the SSSS with uncoated PCM cans and those without energy storage. These findings show the potential for better waste management and renewable energy usage in delivering readily available drinkable water.