Search Results (92)

A CMY palette of ceramic pigments was synthesized using both microwave-assisted firing (800 W, 30 min) and conventional electric firing (1000 °C for 3 h). For the allochromatic vanadium-zircon system (including the non-mineralized green and halide-mineralized blue compositions), as well as the chromium-doped scheelite yellow pigment, microwave firing does not outperform conventional calcination. Although comparable reactions occur during synthesis, microwave firing produces powders with lower colour performance. Nevertheless, these differences become visually negligible after incorporation into glazes. This behaviour can be attributed to the low dopant concentration and the localized, selective heating characteristic of microwave irradiation. In the vanadium-zircon system, the microwave-mineralized sample exhibits features similar to those of the non-mineralized compositions, including lower reactivity, smaller crystallite size, and enhanced blue colour development when applied in glazes. In contrast, for the idiochromatic Zn(Al_1.3Fe_0.5Cr_0.2)O₄ spinel red-brown pigment, microwave firing yields superior colour performance compared with conventional electric firing, producing higher chroma and greater colour intensity. In idiochromatic pigments, the relatively high proportion of chromophore components promotes more homogeneous microwave absorption and heating throughout the precursor mixture. The enhanced colour properties achieved through microwave synthesis may indicate the presence of a beneficial non-thermal microwave effect, leading to improved chromatic performance. Full article

While skeletal imagery appears across various ancient Andean traditions, the Wari Empire (c. 600–1000 CE) developed a uniquely standardized and widespread skull motif—the uma tullu—distributed throughout its former territory. Through an analysis of 63 artifacts spanning ceramic, textile, and metal, this study identifies key diagnostic markers of the motif: the representation of the metopic suture and the application of red pigment. By cross-referencing these stylistic features with bioarchaeological data, the research posits that the uma tullu served as a central communicative device. In the absence of a formal script, this motif may have encoded imperial values and ancestral cult practices, facilitating ideological expansion and state identity. Ultimately, this work demonstrates how standardized iconography functioned as a system of graphic communication and ideological cohesion in the Middle Horizon Andes. Full article

Co- and Ni-doped mullite–spinel ceramics were synthesized via a sol–gel method followed by high-temperature sintering in order to investigate the influence of dopant type on the phase evolution, microstructure, and optical properties. X-ray diffraction analysis confirmed the formation of a multiphase system consisting of mullite and spinel phases, with a residual amorphous fraction, the amount of which decreases with increasing temperature. FTIR and Raman spectroscopy indicate progressive structural ordering of both spinel and aluminosilicate networks during thermal treatment, with differences in crystallization behavior between Co- and Ni-containing system. UV–Vis spectroscopy revealed characteristic absorption bands arising from d–d electronic transitions of Co²⁺ and Ni²⁺ ions in the ceramic matrix, reflecting differences in their local coordination environments and optical behavior. Colorimetric analysis showed that Co-doped samples exhibit intense blue coloration, whereas Ni-doped ceramics display greenish-blue hues. The temperature-dependent evolution of the L*, a*, and b* parameters correlate with structural changes. The results suggest that the type of additive influences the phase evolution and optical response in mullite–spinel ceramics, in agreement with structural and spectroscopic analyses. Full article

This study investigates the composition, morphology and cultural significance of red pigment traces identified on bone pointed tools discovered in the Chalcolithic tell settlement of Pietrele–Măgura Gorgana, attributed to the Kodjadermen–Gumelnița–Karanovo VI cultural complex (4600–4250 BC). The observed use-wear patterns are consistent with repeated contact with soft, non-abrasive materials, including hide working, pigment application on leather or other organic surfaces, fiber manipulation, and perforation of soft substrates. Use-wear analysis revealed polished and flattened distal ends, compatible with repeated use on soft, non-abrasive materials, such as hide, leather, fiber, or other organic substrates. The possibility of pigment application directly on skin, in a practice analogous to tattooing, as previously published, cannot be excluded but remains speculative in the absence of experimental reference data or residue evidence specifically linked to such use. An associated ceramic container was tentatively interpreted as a possible vessel for ochre preparation, suggesting local processing of the pigment. The artifacts were investigated using multi-analytical archaeometric methods: SEM-EDS, AFM, TEM, FTIR, Raman, TGA, CLSM and pseudo-color image segmentation and 3D rendering of porosity distribution. The results consistently identified an iron oxide-based pigment, dominated by hematite and/or goethite, specific to ochre. Pigment particles (50–300 nm) form a well-defined superficial layer on the bone substrate, without Fe–Ca reactions at the interface. The simultaneous presence of Ca, P, Si, Mg and K indicates a silicate matrix with an apatite component, compatible with local and poorly purified raw materials. CIELAB colorimetric analyses revealed significant chromatic variability, suggesting the use of hematite-rich pigments and possible thermal transformations of goethite. The results contribute to the understanding of the pigment technologies of the Chalcolithic communities of the Lower Danube. Full article

This study presents a novel, integrated membrane–resin hybrid platform for the high-efficiency purification of N-acetylneuraminic acid (sialic acid, NANA) from complex microbial fermentation broths. By synergistically combining four sequential stages—ceramic microfiltration (50 nm), ultrafiltration (3 kDa), nanofiltration (150 Da), and dual-resin purification (macroporous adsorption + cation-exchange)—the process achieves stepwise removal of cells, proteins, pigments, monovalent salts, and divalent metal ions without using organic solvents or high-salt buffers. Critically, each stage demonstrates high target recovery: 76.2% (CM), 67.3% (UF), and 77.5% (NF), with near-quantitative retention (>95%) during resin treatment due to NANA’s low hydrophobicity and electrostatic repulsion at pH 6.8. Following optimised acidification crystallisation (acetic acid dosage = 3 × concentrate volume; sialic acid concentrate concentration = 333.49 g/L), the final product reaches 97.9% purity with a crystalline yield of 78.6%. This scalable, green purification strategy eliminates major bottlenecks in downstream processing and enables industrial-scale production of pharmaceutical-grade sialic acid, with broad applicability to other high-value acidic biomolecules. Full article

Aerinite is a rare blue aluminosilicate mineral whose identification as a pigment in Pyrenean medieval artworks typically requires invasive microsampling. This study evaluates portable X-ray fluorescence spectroscopy (pXRF) as a noninvasive screening tool for aerinite in Alto Aragón (Spain) cultural heritage. Elemental compositions of aerinite and lapis lazuli references, ceramics, polychromed capitals, and thirteenth- to fifteenth-century painted panels were measured with a Niton XL3t GOLDD+ spectrometer. Data were analyzed using log-ratio linear discriminant analysis (LDA), with silicon as an internal normalizer. Aerinite references showed Cu and Co levels below instrumental detection limits, along with Fe (6.99 ± 1.04 wt%), Al (4.91 ± 1.38 wt%), and Si (15.95 ± 1.60 wt%). High-confidence aerinite classifications were obtained for Cu-free and Co-free blue pigments in the Barbastro Chrismon, the Buira altar frontal, and other panels. Extension of the protocol to green pigments revealed that two samples—from the Saint Anthony Abbot panel and Portaspana retable—were also classified as aerinite, providing the analytical evidence for “verde de Juseu” as a naturally occurring greenish aerinite variety. Despite known pXRF limitations, this technique effectively screens candidate aerinite-containing passages for subsequent microanalytical confirmation. Full article

The objective of this study was to evaluate whether any coating material would have a beneficial influence on maintaining color stability and surface roughness and to what extent an uncoated resin composite can keep its original color. The study evaluated three direct composite resins (Gradia Direct Anterior A2, Tetric EvoCeram A2, Filtek Z550 A2) using 30 samples per material (1 mm thick, 14 × 10 × 1 mm). Samples were prepared in 3D-printed molds, light-cured for 40 s, and initially smoothed with abrasive paper (grit 400–2000). The surface treatments applied were as follows: group 1—polished with a brush and Compo + polishing paste, group 2—conditioned with 37% phosphoric acid, ScotchBond adhesive applied, light-cured. All samples were cleaned ultrasonically for 5 min. Initial surface roughness and color were measured with a profilometer and spectrophotometer. Samples were then immersed in distilled water (control at 37 °C), Coca-Cola and red wine (at 10 °C) with surface roughness and color changes measurements taken on days 1, 7, 14 and 90. Immersion media were refreshed weekly. The most notable color changes after immersion in coloring solutions were observed in the groups treated with Coca-Cola and red wine compared with the control group in distilled water. Tetric EvoCeram sealed and Gradia sealed maintained the greatest resistance to perceptible coloration over 90 days, while Filtek Z550 performed the poorest. Tetric EvoCeram sealed maintained the greatest color stability (ΔE < 3.5 at 90 days), whereas Filtek Z550 sealed showed early degradation. Roughness is often decreased by surface sealing. As immersion time rises, unsealed surfaces often become noticeably rougher than sealed ones. This study simulates the oral environment and the exposure of restorative materials to staining agents. As the loss of esthetic properties over time is a continuous problem, the clinical significance of this research lies in demonstrating how a restorative material could resist pigmentation, when in contact with well-known high staining beverages, in order to maintain its esthetic properties and remain suitable for long-term use in the oral cavity. Moreover, the hypothesis that a coating material would protect the resin composite surface and reduce discoloration and surface roughness was tested. Full article

This study develops a comprehensive decision-making approach to sustainable product selection for chemical industry supply chains under uncertainty. Five product categories -enamel, ceramics, pigments, non-stick coatings, and glass- were evaluated through fifteen criteria along environmental, economic, and social sustainability dimensions. The hybrid methodology combines Fuzzy SWARA, which weights criteria based on expert opinion, with Fuzzy ARAS, which ranks the alternatives accordingly. The study found that occupational health and safety, consumer safety and health, and water usage are the most important criteria, reflecting a human-centered approach to sustainability decision-making. Ceramics had the best performance score, followed by enamel and non-stick coating. Sensitivity analysis confirmed the robustness of these rankings across various weighting scenarios. The findings indicate that decision-makers in the chemical industry prioritize worker and consumer protection alongside environmental resource stewardship. This framework provides practitioners with a structured method for integrating sustainability considerations into supply chain product portfolio decisions, balancing environmental impact, economic performance, and social responsibility. Full article

Cuprate delafossite phases such as CuMnO₂ (crednerite) and CuFeO₂, as well as iron- and manganese-doped mcconnellite composites, were investigated as candidates for producing intense black ceramic pigments via conventional solid-state synthesis. Both electric kiln and fast dielectric (microwave) firing methods were employed, with mcconnellite (CuCrO₂) used as a reference pigment. Microwave firing led to a marked improvement in sample blackness compared to conventional electric firing. Among the delafossite phases, only mcconnellite subjected to microwave-assisted firing (R_Vis = 1.40%, corresponding to 98.60% visible light absorption) emerges, pending further optimization, as a promising candidate for an ultra-black ceramic pigment (R_Vis < 1%) under optimized glaze conditions (ZnO-free) and a firing temperature of 1000 °C. Considering the pigments in powder form, microwave-fired crednerite (R_Vis = 4.85%, 95.15% absorption) and iron- and iron–manganese-doped mcconnellite composites (R_Vis = 3.27% and 3.23%, respectively) appear as potential candidates for deep-black pigments (R_Vis < 3%), benefiting from the composite effect between the delafossite phase and the associated chromium spinel. Moreover, microwave-fired crednerite also demonstrates noteworthy potential for deep-black coloration in glazed samples (R_Vis = 4.27%, 95.73% absorption). Full article

Identifying the mineral pigments used in the decoration of prehistoric pottery is a significant step for understanding the evolution of the technological practices over time. On the Balkan Peninsula during late prehistory, the techniques used for red and dark-colored decorations underwent a significant transformation. In the Early Neolithic period, pottery was often decorated with dark-toned paints, ranging from deep red to brown. However, this approach declined noticeably during the Chalcolithic period, when red pigment pseudo-incrustation became the predominant decorative method. This study aims to identify the mineral pigments used in red and dark decorations on Neolithic and Chalcolithic pottery from Bulgaria and to trace possible technological, regional, or chronological variations in their composition. A total of 34 ceramic sherds, decorated in shades from red to brown and black, were analyzed using two complementary spectroscopic techniques: laser-induced breakdown spectroscopy (LIBS) and Fourier-transform infrared spectroscopy (FTIR). LIBS data were further evaluated using principal component analysis (PCA) to classify materials based on elemental composition. The results indicate that red decorations are consistently composed of hematite and remain compositionally stable regardless of the region, time period, or application technique. In contrast, dark decorations contain various combinations of iron oxides (magnetite and hematite) and manganese oxides, often including barium-rich manganese compounds—potentially indicating pigment provenance. Additionally, the dark decorations display regional differences. Full article

The potters of Qallaline (or Kallaline, from qallāl, meaning “potters” in Arabic), a district of Tunis (Tunisia) near the now-vanished Bab Kartâjanna gate, produced tiles from the 16th century until the end of the 19th century, with peak activity in the 18th century. These tiles, made from local clay, feature decorations influenced by Hafsid art, the Castilian Renaissance, the Spanish Baroque of the Valencia region, and Ottoman styles. Their characteristic color palette combines green, blue, and ochre. Representative sherds from various 18th-century sites were analyzed using SEM-EDS, portable XRF (pXRF), and Raman microspectroscopy. The results were compared with tiles from earlier (16th-century Iznik, Türkiye), contemporary (18th-century Tekfur Palace, Istanbul, Türkiye), and later (19th-century Naples, Italy) productions used for similar purposes. The chemical signature of the different cobalt ores used appears to depend primarily on the production period. The pastes used in Iznik, Tekfur, and Qallaline ceramics exhibit different compositions. Qallaline potters employed three types of pastes, varying in calcium content, which were used either separately or together within the same tile. In some cases, tin was also present in association with lead. The cobalts used at Qallaline originate from different sources than those used contemporaneously in Meissen (Saxony), as well as from those used in the decoration of Iznik tiles one or two centuries earlier, which are themselves comparable to the cobalt used in Persian mīnā’ī. The As, Ni, and Mn contents are similar to those of the cobalt employed at the Royal Manufacture of Sèvres, believed to have come from the Giftain Valley in Catalonia. Full article

This study investigates the thermally induced phase transformation of Ni-exchanged LTA zeolite as a dual-purpose method for nickel immobilization and the synthesis of stable ceramic pigments. The process describes a cost-effective and sustainable alternative to conventional pigment production, aligning with circular economy principles. Upon thermal treatment at temperatures ranging between 900 °C and 1300 °C, Ni-exchanged LTA zeolite undergoes a transformation to NiAl₂O₄ spinel, confirmed by XRPD, FTIR, and thermal analysis. Initially, NiO is formed, but as the temperature increases, it dissolves and transforms into NiAl₂O₄. Colorimetric studies revealed intensified blue pigmentation with increasing temperature, correlating with crystallite growth and structural evolution. SEM analysis showed morphological changes from cubic particles to sintered agglomerates, enhancing pigment stability and hardness. The Ni-LTA sample calcined at 1300 °C showed the highest hue angle, which was consistent with the formation of over 99 wt.% of the nickel aluminate crystalline phase at this temperature. The results demonstrate that Ni-LTA zeolite can be effectively transformed into durable greenish-blue pigments suitable for application in porcelain. This transformation is especially evident at 1300 °C, where a spinel phase (NiAlSi₂O₄) forms, with colorimetric values: L = 58.94, a* = –16.08, and b* = –15.90. Full article

Twelve sherds of blue-and-white Chinese porcelains recovered from archaeological excavations in the Santana Convent (Ming and Qing Dynasties) in Lisbon were studied using several non-invasive spectroscopies, namely micro-Raman, X-ray Fluorescence (XRF), Ground State Diffuse Reflectance (GSDR), and stereomicroscopy. The use of the X-ray diffraction technique (XRD) allowed us to complete the mineralogical characterization of the ceramic bodies and glazes of the porcelains. The sample selection ranges from the 16th to the 18th centuries. The micro-Raman spectra clearly showed two types of glazes, alkaline glaze and calcium-based glaze. The GSDR absorption spectra of the blue glazes point to the use of different cobalt pigments, but a strong dependence on the glaze type does not seem to exist. The kilns where the porcelains were produced also play an important role. Both the GSDR absorption and the micro-Raman spectroscopies allow us to differentiate the Iranian blue pigment from the Chinese pigment. A direct and simple correlation between the use of Iranian blue pigment, mixtures of Iranian and Chinese pigments, or simply Chinese pigments and the stylistic dating of each sample was established. Furthermore, several important spectroscopic characterizations could be achieved in this study. Full article

Recently, the development of nanoparticle pigments has attracted interest in chemical preparation due to their potential functional properties, such as phosphate-based pigments. The present research focuses on the feasibility of synthesising the BaCr₂(P₂O₇)₂ pigment under hydrothermal conditions. The effect of the microstructural features of ceramic pigments (the crystalline structure, morphology, and particle size) on their optical properties (colour and reflectance) was also studied. The BaCr₂(P₂O₇)₂ compound was prepared in different fluid media, including water and NaOH solutions (0.5–1.0 M), at several reaction temperatures (170–240 °C) and intervals (6–48 h). The single-phase BaCr₂(P₂O₇)₂ did not crystallise without by-products (BaCr₂O₁₀, BaCr₂(PO₇)₂) in water and the alkaline solutions, even at 240 °C for 48 h; in these fluids, the ionic Cr³⁺ species oxidised to Cr⁶⁺. In contrast, the BaCr₂(P₂O₇)₂ single-phase crystallisation was favoured by adding urea as a reductant agent (25.0–300.0 mmol). Monodispersed BaCr₂(P₂O₇)₂ fine particles with a mean size of 44.0 nm were synthesised at a low temperature of 170 °C for 6 h with 0.5 M NaOH solution in the presence of 50.0 mmol urea. The phosphate pigment particle grew to approximately 62.0 nm by increasing the treatment temperature to 240 °C. A secondary dissolution–recrystallisation achieved after 24 h triggered a change in the particle morphology coupled with the incrementation of the concentration of NaOH in the solution. The pyrophosphate BaCr₂(P₂O₇)₂ pigments prepared in this study belong to the green colour spectral space according to the CIELab coordinates measurement, and exhibit 67.5% high near-infrared (NIR) solar reflectance. Full article

Porous silica gel powders, doped with gold nanoparticles (AuNPs), were obtained by heating silica gels containing 1-dodecanethiol and tetrachloroauric acid at temperatures of 450 °C, 700 °C and 900 °C, and characterized using X-ray diffraction, TEM/EDS studies, UV/Vis reflectance spectroscopy and DTA/TG investigations. The color and microstructure of the obtained samples with a composition SiO₂:AuNPs (about 0.03% Au) depend on the heating temperature. The UV/Vis reflection spectra of the samples are explained using Mie’s theory. The thermal stability of the obtained samples, as well as the processes occurring in the sol–gel matrix upon heating, were monitored by DTA/TG. The textural properties of the obtained materials were described based on adsorption–desorption isotherms. The obtained nanocomposites are promising pigments for ceramic glazes, similar to the Purple of Cassius. The textural properties of certain samples, S_BET = 200–350 m²/g, a mean pore diameter (D_AV) of approximately 10 nm and a specific pore volume (V_t) between 0.5 and 0.8 cm³/g, make them promising candidates for catalytic applications, comparable to aerogel-like materials. Full article