Search Results (72)

In the present case study, the manufacturing technology for glazed pottery was investigated, with particular focus on the great variety of colours and glaze recipes used in Western Anatolia and East Asia and observed in finds from rescue excavation sites in Greece. An assemblage of 40 ceramic fragments dating from the Late Byzantine and Islamic to the Ottoman/Venetian periods was examined for their decoration, surface treatment, and production technology. The peculiarities of the colour recipes applied on the glazed pottery of different assumed origins of production were investigated, focusing on glaze technology and employing colourants. This was achieved by the use of an analytical workflow that considered the compositional details of pigments, slip coatings, and glazes. The chemical evaluation was carried out utilising X-Ray Fluorescence Spectroscopy (pXRF) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS). Raman Spectroscopy provided information about the compositional variation, and the microscopic examination via Optical Microscopy (OM) and Scanning Electron Microscopy (SEM-EDS) yielded information about the sample stratigraphy of the examined ceramic sections. Through a wide range of colour and glaze recipes, this study of glazed ceramics was able to define and express the essential elements of each pottery workshop’s perception of colour. Full article

The earliest archaeological evidence of wine came from ceramic vessels of the Transcaucasian ‘Shulaveri-Shomutepe’ or ‘Aratashen-Shulaveri-Shomutepe culture’ (SSC/AShSh: c. 6000–5200 BC). Western European ‘Bell Beaker culture’ (BB: c. 2500–2000 BC) is characterized by bell-shaped pottery vessels but has so far not been found with residues consistent with wine. Knowing that wild grapes populated both habitats, the absence of wine during the Bell Beaker period remains to be explained. The main goal of this work was to investigate whether the shape of the vessels could influence the performance of spontaneous fermentation, specifically regarding the production of volatile acidity. Crushed grapes or juices from various grape cultivars were fermented in two types of vessels: (i) borosilicate glass beakers (4–5 L) to imitate bell beakers and (ii) Erlenmeyer flasks (5 L) to imitate SSC/AShSh vessels. Fermentations occurred spontaneously, and the wines were analyzed for their conventional physical–chemical parameters (e.g., ethanol content, total acidity, volatile acidity, pH), chromatic characteristics (e.g., wine color intensity, wine hue), and volatile composition by gas-chromatography-flame ionization detection (GC-FID). At the end of fermentation, the yeast species were identified by molecular methods. In addition, wine yields and phenolic composition (e.g., total phenols, anthocyanins, total pigments) were determined for wild grapes in comparison with six red varieties Vitis vinifera L. subsp. sativa (Vinhão, Marufo, Branjo, Melhorio, Castelão and Tempranillo Tinto), chosen as a function of their genetic relatedness with the wild counterpart. Wines produced from V. sylvestris grapes showed higher total acidity and color intensity when compared to the cultivated varieties. Saccharomyces cerevisiae dominated at the end of all spontaneous fermentations in all types of vessels and conditions. Wines fermented in Erlenmeyers showed ethanol concentrations as high as 14.30% (v/v), while the highest ethanol level was 12.30% (v/v) in beakers. Volatile acidity increased to a maximum of 4.33 g/L (acetic acid) in Erlenmeyers and 8.89 g/L in beakers. Therefore, the shape of the vessels influenced the performance of fermentation, probably due to the different exposures to air, leading to vinegary ferments more frequently in open mouths than in conical-shaped flasks. These results provide a hypothesis based on fermentation performance for the absence of wine produced in the Iberian Peninsula until the arrival of Phoenician settlers. Full article

The recycling of clay waste from construction debris highly depends on the chemical and mineralogical composition of the waste. Clays and clay minerals are known to be among marginal construction waste, representing an interesting opportunity and platform to produce other low-cost and low-carbon materials due to their possibilities for functional material design, such as adsorbents, drug delivery, catalysts and photocatalysts, and nanocomposites. The present review analyzes a wide variety of mechanisms for encapsulating organic and inorganic species between the layers of clay minerals. Through the compilation of advances in acid activation, exchange of inorganic cations, intercalation, and pillarization, new applications for clay materials are generated, paving the way to a nanometric world with functional, magnetic, adsorption, and catalytic capabilities. New trends are consolidated in the reuse of recycled clays in infrastructure projects, such as hydraulic concrete, water purification, soil fertility, pigments and paints, food packaging and storage, and ceramic appliances. It is concluded that clay waste is suitable to reuse in many industrial products and construction materials, enabling a reduction in the consumption of raw materials. Full article

In this paper, based on our previous expertise on ceramic artifacts, several archaeometric methods applied to some samples collected from the Dudești archaeological site (Oltenia region, Romania) are reported for the first time in the literature. The chemical composition, and microstructural and morphological characterization of these samples offer important conclusions about the processing conditions. Some specific techniques such as X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), stereomicroscopy, environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy provide compositional information about composition and the decay processes. Additionally, the Brunauer–Emmett–Teller (BET) method helps to estimate pore sizes and specific surface areas. A thermogravimetric analysis (TGA/TDG) was used to establish details regarding the production technology and also the raw materials source used to make the ceramics. The obtained results indicated that the ceramics are based on a paste of muscovite and feldspar, with high plasticity, together with quartz and hematite/goethite and calcite, the latter in very low concentrations. According to the obtained results, we could assume that clays from the investigated samples had a low concentration of calcium. Gypsum is present as paste in a very low concentration, identified by the presence of a sulphate group in WDXRF. In the same context, iron oxides have a significant impact on the firing atmosphere of iron-rich clay, resulting in blackening under reducing conditions and a reddish coloration under oxidative conditions. The use of hematite and gypsum as pigments further contributes to the color variations in the pottery. The consistent firing temperature range of 200–600 °C in Dudești pottery implies a standardized production process, the variation in color being dependent on the specific reducing/oxidative regime conditions (reducing atmosphere followed by rapid oxidation). This relationship between clay composition and local sources suggests a connection to Neolithic pottery production in the region and their color depending on the reducing/oxidative regime conditions. Full article

Transition metal complexes have historically played a pivotal role in creating vibrant pigments utilized across artistic mediums such as ceramics, paintings, and glass mosaics. Despite their extensive historical use, our understanding of the mechanisms governing transition metal complex behavior has predominantly emerged in recent times, leaving numerous aspects of this process ripe for exploration. These complexes exhibit striking color variations under diverse conditions when employed in pigment formulations. This review utilizes a bottom-up scientific approach, spanning from microscopic to macroscopic scales, to unravel the molecular origins of the colors generated by transition metal complexes in pigments and ceramic glazes. Advanced spectroscopy techniques and computational chemistry play pivotal roles in this endeavor, highlighting the significance of understanding and utilizing analytical data effectively, with careful consideration of each technique’s specific application. Furthermore, this review investigates the influence of processing conditions on color variations, providing valuable insights for artists and manufacturers aiming to enhance the precision and quality of their creations while mitigating environmental impact. Full article

Egyptian Faience, a revolutionary innovation in ancient ceramics, was used for crafting various objects, including amulets, vessels, ornaments, and funerary figurines, like shabtis. Despite extensive research, many aspects of ancient shabti production technology, chemistry and mineralogy remain relatively understudied from the 21st to the 22nd Dynasty, belonging to a recovered 19th-century private collection. The fragments’ origin is tentatively identified in the middle Nile valley in the Luxor area. Our study focused on a modest yet compositionally interesting small collection of shabti fragments to provide information on the glaze’s components and shabti’s core. We found that the core is a quartz and K-feldspars silt blended with an organic component made of plastic resins and vegetable fibres soaked with natron. The studied shabti figurines, after being modelled, dried, and covered with coloured glaze, were subjected to a firing process. Sodium metasilicate and sulphate compounds formed upon contact of the glaze with the silica matrix, forming a shell that holds together the fragile inner matrix. The pigments dissolved in the sodic glaze glass, produced by quartz, K-feldspars, and natron frit, are mainly manganese (Mn) and copper (Cu) compounds. The ratio Cu₂O/CaO > 5 produces a blue colour; if <5, the glaze is green. In some cases, Mg and As may have been added to produce a darker brown and an intense blue, respectively. Reaction minerals provided information on the high-temperature firing process that rapidly vitrified the glaze. These data index minerals for the firing temperature of a sodic glaze, reaching up to a maximum of 1050 °C. Full article

The recent upgrading of synchrotron radiation (SR) sources has favored, in the last few years, the construction and design of beamlines optimized for the study of cultural heritage materials, which may require ad hoc setups, specific spatial resolutions, and detection limits. In the field of cultural heritage, integrated approaches combining different techniques are often required, even at large facilities, where some beamlines offer the possibility of performing different types of measurements at the same point of analysis, complementing preliminary information usually obtained by conventional laboratory and/or portable in situ methods. An overview of the last ten years of synchrotron applications for the study of pigments is given, with discussion of upstream and downstream challenges to methods and techniques. The possibilities offered by the synchrotron techniques are illustrated by a case study of a particular class of painted ceramics, as an example of different research questions that are solved by a combination of SR-based methods. Full article

Reusing waste as raw materials to produce other materials can entail a decrease in production costs and in the abusive use of natural resources. Furthermore, it can even improve the properties of the end product or material. In this sense, a review of the most relevant literature published in recent decades shows that numerous solutions have been proposed or implemented, such as its use to produce construction materials, catalysts, pigments, pozzolana, refractory materials, glass-ceramic products, etc. Our research group has verified the viability of using different types of waste as secondary raw materials to obtain several types of ceramic, glassy and glassceramic materials, as well as frits. This article highlights several types of industrial waste that have both non-toxic (Li, Ca and Mn) and highly toxic (Cr VI) differentiating elements that can be used in sintering and vitrification industrial processes to immobilise them or render them inert. We studied the compositions and characterised the various materials obtained, conducting toxicity and leaching tests on waste/materials designed with high amounts of chromium. A suggestion for future lines of research has been proposed. Full article

Fábrica de Loiça de Sacavém (ca. 1858–1994) was among the first to produce white earthenware in Portugal, becoming one of the country’s leading ceramic manufacturers during the late 19th to early 20th centuries. Research on white earthenware has accompanied the growing interest in post-industrial archaeology but is still poorly explored compared to more ancient ceramic productions. This study focused on the ceramic body, glazes, and colourants of tableware produced by Fábrica de Loiça de Sacavém during the first 50 years of its activity (1859–1910). A multi-analytical approach was selected to investigate the chemical and mineralogical composition of the ceramic body, glaze, and pigments using optical microscopy, variable-pressure scanning electron microscope energy-dispersive X-ray spectroscopy (VP-SEM-EDS), μ-Raman spectroscopy, μ-X-ray Diffraction (μ-XRD), and reflectance spectroscopy (hyperspectral image analysis). The studied tableware was produced with a Ca-poor siliceous–aluminous white earthenware ceramic body covered with transparent alkali lead or lead borosilicate glaze, and most colourants were complex Cr-based pigments. These results are in agreement with the little documental evidence from this period found in the manufacturer’s archives. Full article

Franklinite-zincochromite-gahnite solid solutions were prepared using ceramic or coprecipitation methods, and their pigmenting capacity as cool ceramic pigments in different glazes (double and single firing frits and porcelain frit) was studied. XRD, UV–Vis–NIR diffuse reflectance, CIEL*a*b* colour analysis, band gap measurements, and the photocatalytic degradation of Orange II were carried out to characterise the samples. The following criteria for high red colouring capacity and high NIR reflectance at the minimum Cr amount were found to be the optimal compositions for an intense reddish cool pigment: Zn(Fe_1.8Cr_0.2), Zn(Al_1.5Cr_0.5) and Zn(Al_1.3Cr_0.5Fe_0.2)O₄. All the powders showed a direct semiconductor behaviour, with a band gap of approximately 2 eV, which fell in the visible range (620 nm); the visible light photocatalysis of Orange II was moderate, but franklinite-zincochromite Zn(Fe_1.8Cr_0.2) stood out compared with silver orthophosphate. Full article

Throughout history, ceramics have been the most abundant artifacts in archaeological discoveries. Within the Neolithic period in present-day Bulgaria, skilled artisans applied additional materials to decorate their pottery, evolving in composition and application techniques such as painting or incrustation. This study is focused on the investigation of white pigments used in decorating Early and Late Neolithic pottery from Madzherito, Kaloyanovets, and Hadzhidimitrovo—archaeological sites located in the Thracian Valley, Central South Bulgaria, affiliated with the cultural groups of Karanovo I and IV. Thirteen ceramic sherds were investigated through archaeometric techniques, including Fourier-transformed infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and laser-induced breakdown spectroscopy (LIBS). LIBS data underwent further analysis using principal component analysis (PCA). The results revealed that calcite, enriched with diverse fillers like quartz, clays, feldspars, and metal oxides, was the primary raw material for white decoration throughout the entire period. Talc emerged as an addition to calcite in the paint of two Early Neolithic sherds. The presence of hydroxyapatite and kaolinite in Late Neolithic pottery was also observed. The inclusion of supplementary ingredients in the primary formula for crafting white decorations signifies either the emergence of novel trends in manufacturing techniques or serves as evidence of vessels imported from adjacent territories. Full article

The preparation of environmentally friendly inorganic encapsulated pigments with a bright color and sufficient stability provides an effective strategy for expanding their applications in plastic, paint, glass, and ceramic decoration. The challenges facing the use of such pigments include the formation of a dense protective coating with the required endurance, the relatively weak color of the encapsulated pigments, and the preferable inclusion particle size. Environmentally friendly BiVO₄ is regarded as a very promising pigment for multiple coloring applications due to its brilliant yellow color with high saturation. However, its poor thermal and chemical stability greatly limit the application of BiVO₄. Herein, we report a sol–gel method to synthesize inorganic BiVO₄@SiO₂ yellow pigment with a core–shell structure. By controlling the synthesis conditions, including the particle size and dispersion of BiVO₄ and the calcination temperature, a BiVO₄@SiO₂ encapsulated pigment with excellent chromatic properties was achieved. The obtained environmentally friendly BiVO₄@SiO₂ pigment with encapsulation modification has a comparable color-rendering performance to BiVO₄, and it has a high thermal stability at 700 °C, excellent acid resistance, and good compatibility in plastics. The present research is expected to expand the application of yellow BiVO₄ pigment in harsh environments. Full article

Stainless steel dust is rich in valuable metal elements including Fe, Cr, Ni and Mn, which can be utilized to prepare Fe–Cr–Ni–Mn series black pigments. Meanwhile, manganese can absorb the majority of the visible light wavelength range, which improves the color rendering performance of Fe–Cr–Ni–Mn series black pigments. However, the coloring mechanism of manganese in the above black pigments is not clear. Therefore, the effect of manganese oxide content on the preparation of spinel-type black pigments from microwave-assisted calcination of stainless steel dust was studied in this work. The results show that with the increase in MnO content in the raw mixture, the crystal plane spacing of black pigments increases from 0.2525 nm to 0.2535 nm, the grain size grows from 61.4619 nm to 79.7171 nm, and the lattice constant grows from 0.8377 to 0.8406 nm. Moreover, the band gap is decreased from 1.483 eV to 1.244 eV, the absorbance increases significantly and has a consistent absorbance in the visible range, and the L*, a* and b* values reduce from 41.8, 0.6, 1.6 to 32.0, 1.0, 0.8, respectively. MnO can react with the spinel in stainless steel dust, forming Mn₃O₄, MnCr₂O₄ and Ni (Fe,Cr)O₄ in the system, with a regular polyhedral structure. The prepared pigments have excellent thermal stability at 1100 °C and good compatibility with transparent glazes, which can be adhered to the surface of ceramic tiles after calcination to demonstrate better compatibility as the content of MnO increases. Full article

Due to the importance of optimizing the manufacture of ceramic pigments, motivated by the increase in prices of both raw materials and energy, and the need to control manufacturing parameters to obtain optimal conditions for the preparation of ceramic inks, two synthesis routes (traditional route and coprecipitation) and two calcination methods (traditional oven and microwave oven) are proposed to obtain the blue ceramic pigment CoAl₂O₄ with the aim of minimizing the use of mineralizers or flux agents and reducing energy consumption in its manufacturing. The pigments prepared were characterized by thermal analysis and structurally by XRD and SEM, with particle sizes below 300 nm observed. Finally, the colorimetric coordinates of glazed tiles with the pigments obtained were characterized. In all cases, the microwave-assisted synthesis increased the color intensity, considerably decreasing the temperature and calcination time, obtaining a particle size under 300 nm with a very narrow size distribution, and substantially improving the energy cost of its preparation and the color development of the final product. The viability of the combination of synthesis by coprecipitation and microwave calcination as a method of industrial preparation of ceramic pigments has been demonstrated. Full article

Cobalt blue ceramic pigments mainly consisting of CoAl₂O₄ are subject to the difficulty of color control. Here, a perspective is reported regarding research on the reasons for color change based on the control of the heat treatment and ratio of components. Macroscopically, the composition of pigment powders determines the color. Microscopically, the crystallite characters including size, cation distribution, and structure have an important effect on the color. The ingredient, structural, and color properties of the pigment powders are analyzed using thermo gravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD) measurement, Rietveld refinement, energy dispersive spectrometer (EDS), and colorimetry analysis. The color is proven to be associated with cation distribution, such as that of Co²⁺ and Co³⁺. It is indicated that high heating temperature, long heating time, and a large proportion of Al³⁺ can, respectively, induce the Co²⁺ and Al³⁺ in tetrahedral and octahedral sites. Full article