ABSTRACT This study investigates technological evolution in 16th–18th century Catalan tin glazes and cobalt blue decorations. Analysis reveals three glaze strategies, highlighting shifts in tin oxide use and cobalt pigment composition. In the 16th century, tin oxide acted as an opacifier and cobalt pigments exhibit low arsenic content with CoO/NiO and CoO/FeO ratios around 1.2. The 17th century shows residual tin and increasing manganese in pigments, while the 18th‐century glazes reintroduce tin with a Co–Ni–Fe–Mn glassy pigment (CoO/MnO ≈ 0.85). Nanometric arsenate particles within glazes produce diffuse brown halos in thin sections, offering a novel microstructural marker for archaeometric studies.

The Qal'a of Beni Hammad served as the capital of the Hammadids in the 11th century and constituted an important enclave for understanding commercial, political and economic relations in the Mediterranean and central Maghreb - present-day Algeria- during the Middle Ages. Despite its importance in the history of the central Maghreb, it is largely unknown in terms of material culture and technology. For the first time, a representative sample of glazed pottery from old archaeological excavations at the Qal'a Beni Hammad has been selected in order to characterise them, shed some light on their production and consumption, and to establish possible links with other Mediterranean enclaves. A ceramic assemblage is examined using a combination of microanalytical techniques (FESEM-EDS, OM, micro-XRD), including the recent discovery of a kiln rod. Two main ceramic groups have been identified, the largest of probable local production, in addition to some overseas imports. The ceramics show a wide range of glazing techniques and decoration methods, including lustre, a technical diversity which indicates the development that glazing technology had reached in the central Maghreb during the 11th C. Finally, the presence of tin oxide in the glazes to achieve opacity confirms the widespread availability and use of tin in the pottery industry during the Hammadid period.

Luster is a composite material consisting of one or several micrometric layers of silver, cuprite and/or copper nanoparticles embedded in a glassy matrix. Its colorful, metallic and iridescent appearance is due to its quantum-confined optical response. Luster is produced by the ionic exchange of Ag+ and Cu+ ions from a precursor for the alkali ions from the glaze and reduction to their metallic state. Luster precursor-paints are composed of copper and silver salts, as well as sulfur compounds. It has long been described that benefits of incorporating Fe2O3 into the precursor-paint. While the beneficial role of Fe2O3 has not been verified nor understood. By producing and analyzing a series of luster layers obtained with various copper/silver ratios, with/without Fe2O3, and with/without a reducing stage during firing, we have revealed the role of Fe2O3. Our results show that it produces an iron sulfate melt which increases the silver uptake but not the copper uptake. Copper facilitates the nucleation and growth of silver nanoparticles, as copper is oxidized while reducing silver to metal. Furthermore, Fe(II), which is present in the glass substrate, acts as an additional reducing agent, facilitating the formation of the nanoparticles. Finally, copper nanoparticles only form in pure copper lusters.

Islamic luster is a ceramic glaze decoration exploiting the quantum-confined optical response of noble metallic nanoparticles to produce a colorful metallic and iridescent appearance. Upon firing, silver and copper initially present in an overpaint diffuse into the glaze and are reduced to Ag 0 and Cu 0 nanoparticles. This study examines the relationship between luster colors and paint composition. The six analyzed shards are 9th century Abbasid polychrome lusters exhibiting green, red, ochre, and brown colors. Key chemical factors are revealed by imaging 16 luster cross sections with different micro- and nanoanalytical methods, including UV-Vis spectroscopy, Ag L 3 -, Cu-, and Fe K-edge micro x-ray absorption spectroscopy (μ-XAS), micro x-ray diffraction (μ-XRD), and field emission scanning electron microscopy (FIB-FE-SEM). These factors connect together (i) the Cu/Ag ratio; (ii) the Cu, Ag, and Fe speciation; (iii) the nature, size, and concentration of metallic nanoparticles; and (iv) the luster color. Notably, the Cu/Ag ratio balances the competitive reactions between Ag + reduction and Cu + disproportionation.

The refractive index is an important parameter for the restoration of historical cultural heritage and for non-destructive optical techniques. In this study, different mathematical models for lead glasses were assessed in order to analyze their feasibility to calculate the theoretical refractive index of the historical enamels in stained-glass windows. The models selected were those specifically developed for lead glasses: the Appen method (1949), the Fanderlik and Skrivan model (1972), and the Bonetti and Salvagno method (1983). The results of the mathematical methods were compared with the real values analyzed via ellipsometry. The historical enamels were determined on non-prepared samples, taking into account the Cauchy model in order to avoid damaging the historical pieces. We show that the measured refractive indices of the historical enamels (1.59-1.66) are higher than the values of the lead glasses in the literature (1.55-1.57). The PbO and B2O3 were the compounds that most influenced the value of the refractive index; nevertheless, the presence of metallic elements increased their value compared to pure lead glasses. In addition, the presence of a thin layer of grisaille on the historical enamels and the formation of alteration layers could also modify the real value of the refractive index. As far as theoretical calculations are concerned, the mathematical model of Bonetti and Salvagno (1983) seems to be the most accurate model for this material, with errors < 0.04 units. None of the three models work for glasses with >60% PbO, which is not common in cultural heritage.

This Element, authored by a team of specialist researchers, provides an overview of the various analytical techniques employed in the laboratory for the examination of archaeological ceramic materials. Pottery represents one of the earliest technical materials used by humans and is arguably the most frequently encountered object in archaeological sites. The original plastic raw material, which is solidified by firing, exhibits a wide range of variations in terms of production methods, material, form, decoration and function. This frequently presents significant challenges for archaeologists. In modern laboratories, a variety of archaeometric measurement methods are available for addressing a wide range of archaeological questions. Examples of these include determining the composition of archaeological materials, elucidating the processes involved in manufacturing and decoration, estimating the age of archaeological material, and much more. The six sections present available methods for analysing pottery, along with an exploration of their potential application.

The formation of lead apatites in heritage objects is increasingly recognized as a recurrent phenomenon, however their origins and formation mechanisms remain poorly understood. This study explores the process behind the darkening and surface clouding in Roman fresco paintings, providing novel insights into the formation of lead-calcium phosphates, PbxCa(5-x)(PO4)3Cly(OH)(1-y), and plattnerite, β-PbO2, from the pigment minium, Pb3O4, linked to interactions with environmental factors and dust deposition. A combination of microanalytical techniques was used, including optical microscopy, scanning electron microscopy and elemental analysis, synchrotron-based X-ray diffraction and Raman and FTIR spectroscopy. The results show that slightly acidic rainwater or atmospheric moisture reacts with the minium and the calcium carbonate present in the wall painting's binder, resulting in the formation of plattnerite and the release of Pb2+ and Ca2+ ions, while the environment supplies chloride and phosphate ions, present in the infiltrating water. This process culminates in the precipitation of the lead-calcium apatite, due to its high stability. This apatite acts as a cement that incorporates dust and organic residues, forming a layer several tens of micrometres thick that tends to expand outwards. These findings contribute to a better understanding of pigment degradation mechanisms and will help inform conservation strategies.

El procés de carbonatació en una pintura al fresc segueix els mateixos processos que en els sistemes biogènics. S’inicia amb la formació de carbonat de calci amorf hidratat, CaCO3·nH2O, que s’estabilitza a la superfície de les pintures, tant en morters calcítics com dolomítics, i a l’interior es transforma en calcita, o calcita i aragonita quan el morter és dolomític. En els morters dolomítics, l’hidròxid de magnesi no reacciona amb el CO2 mentre quedi hidròxid de calci per carbonatar, esdevenint, per tant, morters més reactius a llarg termini

Stained-glass windows are often painted with grisailles and enamels. These glassy materials have a low melting temperature and are fixed to the base glass by firing processes. Lead and/or boron are commonly added to the painting material to lower their melting temperature so that they can melt without deforming the glass support. In the present study, model glass samples (with well-known boron content), replica and historical materials were analysed for their composition using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Laser Induced Breakdown Spectroscopy (LIBS). The imprint left on the analysed samples after laser irradiation was observed using optical profilometry. The feasibility of using LIBS in situ as a suitable quantitative analytical technique to detect the presence of boron in historical enamels even in very small quantities was assessed. Quantitative information on historical Spanish enamels and grisailles was obtained from calibration curves generated from the model glass samples with known boron content. The proposed procedure enables a satisfactory chemical quantitative study of historical glass materials in situ, regardless of their size, provenance, and chronology.

The production and distribution of stained glass in Mediterranean Europe during the Middle Ages remains inadequately understood. This article focuses on Catalonia, where local glass production is documented as early as the 13th century, but little is known about the production of window glass. This study analyses a collection of stained glass fragments from Girona Cathedral, dating from the 13th to the 16th century, some of which is the work of renowned master glassmakers. The data obtained is compared with contemporary stained glass documented from other parts of Europe, and with a collection of 15th and 16th century archaeological window glass from Barcelona. The data is also contrasted with historical documentation on glass production in Catalonia. The findings reveal that the glass from Girona from the 13th and 14th centuries is of the potassium-lime type, similar to that produced in the workshops of north-western France. By the late 14th and 15th centuries, the composition aligns more closely with that of north-eastern France. In the 16th century, however, the glass changes to a soda-lime composition, similar to the glass found in Barcelona, suggesting a transition from central European to Mediterranean sources, and indicates a change in the raw materials involving the use of soda-lime plant ash instead of potassium-lime forest ash. These results indicate that the production of window glass shifted from France to Barcelona at the close of the 15th century. (c) 2025 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC license ( http://creativecommons.org/licenses/by-nc/4.0/ )

A group of a well-known polychrome glazed ceramic, widespread in the western Mediterranean in the eleventh and first half of the twelfth centuries, has been analysed for the first time using Optical Microscopy (OM) and a Field Emission Scanning Electron Microscopy (FE-SEM) with Energy-Dispersive X-ray Spectroscopy (EDS), in order to shed some light on the materials, production technology and provenance, about which there are various hypotheses. This ware is characterised by a perfectly drawn and varied iconography, with often stylised zoomorphic and anthropomorphic and nautical motifs. It was produced in an as yet unidentified workshop in North Africa or the Iberian Peninsula. The pottery analysed was found in an archaeological excavation in the Barrio Andalusi of Almería (south-east of Spain). Technologically, the ceramics are fairly homogeneous, with copper-green and manganese-brown pigments applied over the raw tin glaze filled with large undissolved quartz particles. The use of quartz is consistent with a Fatimid-Zirid contribution from Ifriqiya, the use of tin is consistent with an Andalusi Umayyad-Taifas contribution, and the green and brown colours on a white ground to either Ifriqiya or Andalusi. Our study has shown that the use of quartz on the decorated glazed surface is not related to the need for an opacifier, but rather to the need for a highly viscous melt that limits the spread of the pigments during the firing allowing a finer and more detailed drawing. This fusion of different techniques has been identified for the first time. It is intriguing from the historical point of view of medieval technology, and provides the first insights into understanding the technological transfers and technical solutions that took place in the Mediterranean basin during this period.

Little is known about the materials used in the manufacture of red window glass in the 19th and the first decade of the 20th century. Here, we have studied fragments from eight Spanish glasses from the 19th and 20th centuries. The red glasses consist of a single layer of red glass on a colourless glass substrate. The chemical composition, oxidation state, nature of colourants and crystalline precipitates were determined by a selection of microanalytical techniques. In the study, we have found that the red colour of the glass is due to the presence of Cu0 nanoparticles, the red glass layer has lower calcium content than the substrate glasses, which we found favours copper being present in the glass predominantly in Cu+. They also contain tin and iron while lead, described in historical and modern documentation, was absent. Tin must have been added to the glass as a Sn2+ compound and acted as a reducing agent for copper. Iron is also a well-known reducing agent, but does not act as such in the red glasses studied here. However, it may have facilitated the reduction of copper to Cu0 by promoting its incorporation into the glass as Cu+ rather than Cu2+. (c) 2023 The Authors. Published by Elsevier Espa & nacute;a, S.L.U. on behalf of SECV. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).

The opacity/transparency, color, and production of designs in Changsha ware, a Tang dynasty Chinese stoneware renowned for its polychromy and pioneering high-temperature red glaze, are studied by analyzing the composition, micro/nanostructure, and copper/iron speciation. The results shed new light on some of the most debated questions about Changsha ware. In particular, the role of glaze thickness, composition, and firing conditions on the coexistence of transparent and opaque glazes and of oxidized green and reduced red copper designs on the same object, and on the reason for the development of either green or turquoise colors. New data obtained by reproducing a copper red overglaze and underglaze painting with a similar glaze composition and thickness have provided new insights into the origin of the first high-temperature copper reds and, in the absence of essential knowledge, their discontinuity. This study also contributes to the long debate regarding the use of overglaze versus underglaze painting techniques.

A small group of ceramics from the archaeological excavations at Tahert (Algeria), the seat of the Rustamid dynasty in the 9th-early 10th centuries, has been studied for the first time by OM, SEM-EDS and micro X-ray diffraction. The ceramics belong to the earliest glazed pottery workshop found in North Africa, as other earlier or contemporary workshops in Tunisia and Egypt have not yet been found. The analysis made it possible to characterise the production of polychrome transparent lead-glazed wares, to distinguish it from other glaze workshops, and to trace links with other glaze workshops of Dar al-Islam, such as those producing 'Raqqada Yellow' ware. Furthermore, the polychrome glaze production of Tahert is a clear example of how migrating potters, although using the same technique, adapted to the raw materials and geographical conditions of the new area.

Little is known about the production of ruby red copper stained glasses from the Medieval and Renaissance periods apart from the fact that the colour is due to the presence of small metallic copper nanoparticles and that tin, the most common reducing agent used in copper red glass production since the 19th century, is not present. In fact, very few workshops in Europe were able to make red glass in historical times, and they kept it secret, so very little is known about how it was obtained. These workshops exported the red glass throughout Europe. Recently, the presence of copper sulphide particles and the data obtained in the replication red glass following historical recipes suggested that sulphur might be the key ingredient in this process. Here, a collection of historical red glasses from these periods has been analysed using a combination of microanalytical techniques; Electron Microprobe (EM) and Field Emission and Scanning Electron Microscopy (FESEM) to verify the chemical composition and nanostructure of the glasses, Synchrotron radiation micro-X-Ray Diffraction (micro-XRD) to establish the nature of the nanocrystalline precipitates, and S, Cu and Fe K-edge micro-X-Ray Absorption Spectroscopy (micro-XAS) to determine the speciation. The data obtained show that the oxidation of S2-into S6+ in the glass is responsible for the precipitation of copper nanoparticles. The develop-ment of a sulphide-silicate partition and the presence of Fe3+ in the melt give rise to the precipitation of the high-pressure tetragonal polymorph of chalcocite (Cu2S). Differences between the Medieval and Renaissance red glass are determined.

Excavations in the former Roman port of Utica (North Tunisia) by the University of Oxford and the INP (Tunisie) have revealed an area of medieval Islamic houses in the area of the Roman forum. Stratified sequences of pottery have established four main phases of occupation which would appear to span the mid-10th to mid-11th century. The range of glazed wares and other classes of pottery is summarised per phase and a detailed study of the glaze technologies of 23 samples through time can now be compared with the study of 14 vessels previously published from Bir Ftouha, near Carthage. The Utica assemblage demonstrates that there were major changes in the consumption of glazed wares from the late Fatimid period to Zirid independent rule, not only in relation to forms and types of decoration but also in terms of glazing techniques. Up to six different glazing techniques have been identified, including transparent and opaque glazes and overglaze and underglaze decoration. Moreover, the presence of several glaze imports has been detected, showing that glazed pottery other than those produced in the central region of Ifriqiya was being consumed in North Tunisia. This work also provides relevant information with regard to the production and consumption of glazed wares in medieval Tunisia during the 10th and 11th centuries.

Medieval texts describe the use of the three-tone system as a pictorial procedure characteristic of Ro-manesque art to represent shape and volume. Some Medieval art treatises provide detailed instructions of its application, using specific names for each of the carnation colours: membrana (mid-tone or base colour), rosa and posc (darker) and lumen (lighter). In this study we have verified its use and application by analysing the mural paintings of the central apse of the church of Sant Climent de Taull (Catalonia), currently on display at the Museu Nacional d'Art de Catalunya. A combination of microanalytical tech-niques, micro-infrared spectroscopy (& mu;FTIR), synchrotron-based micro-X-ray diffraction (& mu;SR-XRD), Scan-ning Electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and Optical microscopy (OM), provided precise information on the composition and distribution of the compounds in the se-quence of micrometric layers. We have identified the use of up to eight different pigments carefully mixed, to obtain a variety of tones in accordance to the recipes given in the Theophilus' De diversis Artibus and the Hermeneia (Byzantine pictorial tradition). The inner layers, painted directly on the still wet lime mortar, show the typical carbonation microstructure of fresco, while the surface layers for the contours of geometric decorative elements and figures which required longer working times, were applied al secco. & COPY; 2023 The Authors. Published by Elsevier Masson SAS on behalf of Consiglio Nazionale delle Ricerche (CNR). This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

En los últimos años se ha investigado la tecnología de producción del vidriado altomedieval en la Península Ibérica con el objetivo de comprender su origen, ya que, tras la época romana, la ceramica vidriada deja de producirse en Iberia. Para ello, se ha estudiado la cadena operativa en la producción de la cerámica vidriada en al-Andalus, concretamente en los primeros talleres donde se produjo, Pechina, Córdoba y Málaga (siglo IX). Aunque al principio se pensó que la tecnología procedía del Oriente islámico, finalmente se ha demostrado el carácter autóctono de la misma. Los vidriados transparentes de alto contenido en plomo se fabricaron a partir de vidrio de plomo, dándose, por tanto, una transferencia tecnológica directa entre el vidrio y el vidriado. La producción de objetos a partir de vidrio de plomo es muy inhabitual en el mundo Islámico por lo que la producción de los mismos en al-Andalus resulta ya en sí misma muy sorprendente. Aunque inicialmente se consideró también la posibilidad de que la cerámica vidriada estuviera relacionada con la "vetrina pesante" que se produce en Italia, y con otros centros productores islámicos del Mediterráneo hemos comprobado que no existe ninguna relación. En cambio, la tecnología del vidriado blanco de estaño llegó a al-Andalus, a principios del siglo X, procedente del mundo abasí, junto con otras innovaciones en la producción cerámica. Gracias a los hallazgos del taller de Córdoba, también se ha podido comprender la "chaîne opératoire" del vidriado opacificado con estaño. Cabe destacar que, según los datos actualmente disponibles, al-Andalus fue el primer territorio islámico del Mediterráneo occidental en desarrollar esta tecnología y no utilizó partículas de cuarzo para producir vidriados blancos opacos para las cerámicas vidriadas decoradas, como ocurre en Ifriqiya o Sicilia.

Jun ware is stoneware created in the late Northern Song dynasty (12th century) with a blue glaze combining transparent-blue and whitish-opaque submillimetric areas. The glaze has a glass nanostructure with lime-rich droplets in a silica-rich matrix resulting from a high temperature liquid-liquid phase separation. Calcium-rich opaque and calcium-poor transparent areas are combined. Iron is more oxidised in the calcium rich areas (approximate to 17-20% Fe2+) than in the calcium poor areas (approximate to 60-70% Fe2+) of the glaze. Therefore, iron is oxidised in the lime-rich droplets and reduced in the silica-rich matrix. The sky-like appearance of the glaze is due to the combination of the light absorption in the transparent-dark-blue Fe2+ rich areas and scattering in the white-yellowish Fe3+ rich areas. Copper appears mainly oxidised but in the red areas a few small copper nanoparticles are present and iron appears more oxidised. The result indicates the simultaneous reduction of copper and oxidation of iron.

A High Temperature Synchrotron Radiation X-Ray Powder Diffraction experiment was performed to determine the manganese compounds formed during the heating and cooling of 70 wt% PbO - 30 wt% SiO2 mixture or the equivalent glass plus 10 wt% of MnO. The effect of adding calcite, dolomite and kaolinite were also studied. All mixtures were fired between 690 degrees C and 1020 degrees C in oxidizing conditions and analysed by Scanning Electron Microscopy. A sequence of manganese phases are formed during firing: bixbyite (Mn2O3), barysilite ((Pb,Mn)Si2O7), kentmlite (Pb2Mn2Si2O9) and braunite (Mn7SiO12). Kentrolite and braunite crystallise with different crystal habits during the heating and the cooling. If dolomite is present diopside ((Ca,Mg,Mn)(2)Si2O6) is formed. If calcite is present, ganomalite (Pb-3(CaMn)(2)Si3O11), margarosanite (Pb(Ca,Mn)(2)Si3O9) and wollastonite ((Ca,Mn)SiO3) are also formed. Wollastonite can incorporate enough manganese to transform into bustamite ((Mn,Ca)(3)Si3O9) at high temperatures. This leaves less manganese available for the crystallisation of kentrolite and braunite.