Glazes add value to ceramic, improve its appearance (colour and shine) and make it waterproof. Through the choice of colours and designs, glazes made ceramics fashionable, even luxurious, and ...therefore, an object of trade. Each region and ruling dynasty developed its own style or trademark which makes them particularly suitable for dating purposes. Therefore, the study and analysis of glazes offers direct information about the acquisition of technical skills (technology), trade of specific materials (inter-regional links), migrations and the introduction/adoption of new trends. A ceramic glaze is a thin glassy layer fused to the surface of a ceramic body through firing. The interaction between the glaze and the ceramic body results in the interdiffusion of elements between both. A glaze consists mainly of an amorphous phase, but also includes bubbles, cracks and crystalline phases (undissolved compounds and crystals formed during the firing). Finally, the glazes were also decorated, and a large variety of materials and methods of applying the decorations were used. In this chapter, we present a summary of the technical characteristics of glazes (composition, microstructures and technical requirements), their discovery and use throughout history and decorative techniques. The methodology and analytical techniques to obtain the information are also discussed.
The first workshop evidence of the Caliphate polychrome tin-glaze production known as ‘verde y manganeso’ in
al-Andalus
has been found in the Cordoban workshops area. This study reports on the ...analysis of recovered firing debris and workshop items and the tin glaze production chaîne opèratoire using SEM-EDS and μ-XRD analysis. The findings reveal the use of a tin and lead
calx
mixed with plant ashes both in the Emirate and later Caliphate tin glaze productions and demonstrate a direct relationship between the Umayyad Córdoba-
Madīnat al-Zahrā’
and the Abbasid regions. Moreover, ceramics from both domestic and palatial well-dated archaeological contexts from Córdoba and
Madīnat al-Zahrā’
have been analysed to determine the differences among the domestic and palace wares and to shed light on the long running dispute among scholars regarding the location of the tin-glazed workshops. Our data demonstrate so far that the workshop area of Córdoba manufactured ‘verde y manganeso’ tin-glazed ceramics during the Caliphate period and that it could have been supplying both high-quality wares for the palaces and cheaper products for the domestic contexts.
The earliest glazed ware in al-Andalus is dated to the Emiral period (c. 850–875 CE) and is not until the Caliphate of Córdoba (929–1031 CE) that a distinctive polychrome tin glaze started being ...produced. A short transition period (c. 875–925 CE) in which elaborate monochrome and bichrome transparent glazes wares coexist with polychrome transparent and tin opaque glazed wares has been identified. The existence of a polychrome lead transparent glaze production in al-Andalus wares is demonstrated; it has distinctive composition and methods of production from monochrome and bichrome wares, and shares a distinctive absence of foot and overglaze application of the decorations with the tin-opacified wares. With regard to the possible routes of the introduction of the polychrome lead and tin glazes into the western Mediterranean the Tunisian connection seems completely discarded. Moreover, and although some similarities between the Cordoba and the Abbasid productions such as similar tin glaze recipe and decorative patterns and use of lead glazes, can be traced, the dissimilarities, such as, the use of overglaze decorations, absence of alkali transparent glazes, variances in the tableware shapes and absence of foot, are still more important, and do not support a clear link between them.
•The transition from lead transparent to tin opacified glazes in al-Andalus is studied.•Three different technological glaze traditions are determined.•The Abbasid world appears the most probable connection for the al-Andalus tin glazes.
A set of the Classic and official Jun ware shards found at various kilns at Yuzhou (Henan) are analyzed. The blue color and milky appearance of the glazes subject of intense debate as being due to ...either the glaze nanostructure or chemistry. The presence of submillimetre areas showing different color and opacity gives to the glazes a three dimensional cloudy sky appearance. Nanostructure and chemistry of the glazes, oxidation state of iron and nature of the copper nanoprecipitates are studied at a submillimetre level. Images of the glaze nanostructures are obtained using a Focus Ion Beam and Scanning Electron Microscope with nanometric resolution. The size and volume fraction of the nanostructures determined by image treatment are related to the chemical composition of the glazes. Differences between kiln productions are found and the origin of the color and opacity of the glazes discussed in terms of the chemistry and nanostructure.
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+.
Poco se sabe sobre los materiales utilizados en la fabricación de vidrios rojos planos en el siglo xix y primera década del xx, por ello se han estudiado ocho fragmentos españoles de la época. Todos ellos están formados por una sola capa de vidrio rojo sobre un sustrato de vidrio incoloro. La composición química, el estado de oxidación, la naturaleza de los colorantes y los precipitados cristalinos se han determinado mediante una selección de técnicas microanalíticas. Hemos encontrado que la capa de vidrio rojo contiene nanopartículas de Cu0, y que tiene un menor contenido de calcio menor que el vidrio sustrato, lo cual favorece que el cobre esté en el vidrio predominantemente como Cu+. Tal y como está descrito en la documentación histórica y moderna contienen estaño y hierro, pero no se ha verificado la presencia de plomo. El estaño se agregó al vidrio como un compuesto Sn2+ y actuó como agente reductor del cobre. El hierro a pesar de ser un agente reductor, no actúa como tal en los vidrios rojos estudiados. Sin embargo, su presencia podría facilitar la reducción del cobre a Cu0 al promover su incorporación al vidrio como Cu+ en lugar de Cu2+.
Resins obtained from
Pinus
genus species have been widely used in very different fields throughout history. As soon as the resins are secreted, molecular changes start altering their chemical, ...mechanical and optical properties. The ageing processes are complex, and the chemical and structural changes associated with resin degradation are not yet fully known. Many questions still remain open, for instance changes happening in pimaranes, one of the two diterpenoid constituents of the resin. A systematic study of the ageing process of
Pinus
resins is done through Fourier transform infrared spectroscopy (FTIR) using chemical standards and complementing the obtained results with gas chromatography coupled to mass spectrometry (GC/MS) analysis when necessary. Moreover, long-term degradation processes are also investigated through the analysis of a selection of dated historical resins. This study overcomes the limitations of GC/MS and brings new information about the reactions and interactions between molecules during
Pinus
resin ageing processes. It also provides information about which bonds are affected and unaffected, and these can be used as specific markers of the degradation and of the resins themselves.
Graphical Abstract
Changes in the IR spectral features due to the
Pinus
resin ageing processes
The study and analysis of the materials found in one of the earliest Islamic glazed ceramics workshop in al-Andalus (Pechina) dating from the second half of the 9th century, including fritting ...vessels, kiln furniture, wasters and slags, and a glass chunk, have revealed the materials used and methods of production. Galena was oxidised to obtain PbO in the workshop. Fritting of the glaze involved a two-stage process for which two different types of vessels were used. The fritting process ended with a melt which was poured to obtain a high-lead glass. The ground glass was applied over the biscuit-fired ceramics, and fired to a temperature high enough to soften the glaze and adhere it onto the ceramic surface. Evidence of a similar process was found in a later workshop in San Nicolas (10th century) which demonstrates the persistence of the technique in al-Andalus during the caliphal period. There is little evidence of early Islamic glaze manufacture at kiln sites, and in contrast to the glass workshops, the glazed ceramics workshops have not been studied. Consequently, this study adds valuable information to the currently very limited knowledge about the early glaze technology in Dar al-Islam.
The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Iraq in the 9th century AD with the production of a range of glazed wares in response to the import of ...Chinese stonewares and porcelains. However, Oliver Watson has recently proposed that the demand for Islamic glazed pottery first occurred in Egypt and Syria in the 8th century AD resulting in the production of opaque yellow decorated wares. Using a combination of SEM analysis of polished cross-sections, and surface analysis using hand-held XRF or PIXE, Coptic Glazed Ware from Egypt, Yellow Glazed Ware from Syria, and comparable wares from Samarra, Kish and Susa have been analysed. The analyses show that the opaque yellow decoration was the result of lead stannate particles in a high lead glaze, which it is suggested was produced using a lead-silica-tin mixture. The use of lead stannate in the production of yellow opaque glazes is explained in terms of technological transfer from contemporary Islamic glassmakers who continued the Byzantine tradition of glassmaking. It is further argued that the introduction of opaque yellow glazed pottery into Mesopotamia could have provided the social context for the sudden emergence of tin-opacified white glazed pottery in Abbasid Iraq in the 9th century AD. However, in view of the very different glaze compositions employed for the yellow and white opaque glazes, it seems probable that the white tin-opacified glazes used for Abbasid cobalt blue and lustre decorated wares represent a separate but parallel technological tradition with its origins in the production of Islamic opaque white glass.
•Lead stannate used to produce yellow opaque glazes in Egypt and Syria in 8th century AD.•Use of lead stannate reflects awareness of Byzantine glassmaking technology.•Yellow glazed ware provided social context for emergence of Abbasid white glazed ware.•Yellow and white glazed wares could represent separate but parallel technological traditions.•In Egypt, there was a switch back to lead antimonate for yellow opaque glazes.
Color and dichroism of silver-stained glasses Molina, Gloria; Murcia, Sonia; Molera, Judit ...
Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology,
09/2013, Letnik:
15, Številka:
9
Journal Article
Yellow decorations in glasses have been produced since the beginning of the fourteenth century by incorporating metallic silver nanoparticles into the glass (from a few to some tens of nanometers). ...The optical response of the glass-particles composite is determined by the surface plasmon resonance absorption and scattering of the nanometric metallic particles. Generally, the same color is perceived in reflection and in transmission although dichroic effects are occasionally observed. As silver-stained glasses were designed to be observed in transmission, tuning the transmission color from yellow to red was of technological interest. The relationship between the color observed both in transmission and reflection and the composition and nanostructure of regular (yellow) and dichroic (yellow and red) silver stains from the Renaissance (late fifteenth and sixteenth century, respectively) is related to the presence of a layer (of about 10–20 μm thick) of metallic silver nanoparticles (from few to 100 nm in size). The correlation between the colors observed and the silver stain nanostructure is studied with particular emphasis on the origin of the dichroic behavior. The optical response is computed and compared to the experimental data. Differences in the synthesis parameters responsible for the colors and for the dichroic behavior of the silver stain glasses are proposed. This is essential for the replication of the glass pieces which are required as replacements in the restoration/conservation of the windows but is also of broader interest.
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