Azulejo blues – An analytical study of the blue colours in portuguese azulejos

This communication reviews the main variants of the blue colour found on glazed tiles (mainly of Portuguese manufacture) used in Portugal from the 16th to the late 18th centuries and discusses the composition of the pigments from which they result

The use of micro-XRD for the study of glaze color decorations

The compounds responsible for the colours and decorations in glass and glazed ceramics include: colouring agents (transition metal ions), pigments (micro-and nano-precipitates of compounds that either do not dissolve or recrystallize in the glassy matrix) and opacifiers (microcrystalline compounds with high light scattering capability). Their composition, structure and range of stability are highly dependent not only on the composition but also on the procedures followed to obtain them. Chemical composition of the colorants and crystallites may be obtained by means of SEM-EDX and WDX. Synchrotron Radiation micro-X-ray Diffraction has a small beam size adequate (10 to 50 microns footprint size) to obtain the structural information of crystalline compounds and high brilliance, optimal for determining the crystallites even when present in low amounts. In addition, in glass decorations the crystallites often appear forming thin layers (from 10 to 100 micrometers thick) and they show a depth dependent composition and crystal structure. Their nature and distribution across the glass/glazes decorations gives direct information on the technology of production and stability and may be related to the color and appearance. A selection of glass and glaze coloring agents and decorations are studied by means of SR-micro- XRD and SEM-EDX including: manganese brown, antimony yellow, red copper lusters and cobalt blue. The selection includes Medieval (Islamic, and Hispano Moresque) and renaissance tin glazed ceramics from the 10th to the 17th century AD

Hispano-Moresque ceramic tiles from the Monastery of Santa Clara-a-Velha (Coimbra, Portugal)

A group of late 15theearly 16th century Hispano-Moresque glazed tiles from the Monastery of Santa Clara-a-Velha, in Coimbra, were, for the first time, characterised chemically and morphologically. Since the prevailing idea among art historians in Portugal is to judge the Hispano-Moresque tile heritage as Spanish production, the findings concerning technological processes were compared with the Islamic technology in the Iberian Peninsula and latter Hispano-Moresque in Spain. This study is the first analytical indicator of a production technology with some differences from the Hispano-Moresque workshops (such as Seville, Toledo, etc.) and points out to a possible local production. Five different coloured glazes were identified: white, blue, green, amber and black, all displaying high-lead content, as expected for this type of ceramics. Tin oxide was identified in high contents (7e14 wt.%) in white and blue glazes, its crystals homogenously distributed in also very homogeneous glazes, showing similarities with an Islamic glazing technology. On the other hand, Ca-rich thick glazeeceramic interfaces were observed, with many mineral inclusions (wollastonite (CaSiO3) and also K-feldspars (general formula KAlSi3O8), showing a higher resemblance with a later Hispano-Moresque technology. Other compounds were also identified from reactions involving the colour compound: malayaite (CaSnOSiO4), bustamite (CaMnSi2O6), braunite ((Mn2þ, Mn3þ)6O8SiO4), andradite (Ca3Fe2Si3O12), magnesioferrite (MgFe2O4) and a nickel ferrite (NiFe2O4). The chemical composition of this glazeeceramic interface suggests firing temperatures between 950 C and 1000 C and its thickness implies a single-fire process. The chemical characterisation does not suggest different recipes or different firing processes for cuerda seca and arista tiles

White on blue: A study on underglaze-decorated ceramic tiles from 15th-16th-century Valencian and Sevillian productions

This study characterises and compares tin-opacified underglaze-decorated tiles from Valencian and Sevillian provenances. This technique, where the cobalt and manganese pigments are applied below an opaque white glaze, was used in the Iberian Peninsula between the 14th and early 16th centuries. The chemical and morphological characterisation of the glazes was performed by Optical Microscopy (OM), Scanning Electron Microscopy with Energy-Dispersive X-Ray Spectroscopy (SEM-EDS), μ-Raman Spectroscopy, and μ-Particle-Induced X-Ray Emission (μ-PIXE). Both the morphology of the glazes and their chemical composition allowed for the distinction between the two production centres. Sevillian glazes exhibit a thicker pigment layer, as well as higher SnO2 and lower K2O contents than the Valencian ones. Furthermore, the SEM analysis of cobalt pigment particles identified an interior nucleus rich in Co, Fe and Ni, and an exterior layer rich in Si, Ca, Mg and Na,suggesting that the pigment was used mixed with clay or sand

Mineralogical Characterization of Hispano-Moresque Glazes: A μ-Raman and Scanning Electron Microscopy with X-Ray Energy Dispersive Spectrometry (SEM-EDS) Study

This work explores the combination of μ-Raman spectroscopy and scanning electron microscopy with X-ray energy dispersive spectrometry (SEM-EDS) for the study of the glazes in 15th–16th century Hispano-Moresque architectural tiles. These are high lead glazes that can be tin-opacified or transparent, and present five colors: tin-white, cobalt-blue, copper-green, iron-amber, and manganese-brown. They are generally homogenous and mineral inclusions are mostly concentrated in the glaze-ceramic interface. Through SEM-EDS, these inclusions were observed and chemically analyzed, whereas μ-Raman allowed their identification on a molecular level. K-feldspars, wollastonite and diopside were the most common compounds, as well as cassiterite agglomerates that render the glaze opaque. Malayaite was identified in green glazes,and andradite and magnesioferrite in amber glazes. Co–Ni–ferrites were identified in blue glazes, as well as Ni–Fe–olivines. Manganese-brown is the color where most compounds were identified: bustamite, jacobsite, hausmannite, braunite, and kentrolite. Through the μ-Raman analysis of different areas in large inclusions previously observed by SEM, it was possible to identify intermediate phases that illustrate the reaction process that occurs between the color-conferring compounds and the surrounding lead glaze. Furthermore, the obtained results allowed inference of the raw materials and firing temperatures used on the manufacture of these tiles

The Glaze Technology of Hispano-Moresque Ceramic Tiles: A Comparison Between Portuguese and Spanish Collections

For the first time, Hispano-Moresque glazed tiles from Portuguese and Spanish collections were studied together and compared. This work is included in a wider study tackling the technology of Hispano-Moresque tile production from several collections in the Iberian Peninsula. While showing many similarities, differences were identified between collections, regarding both chemical and morphological characteristics. The collection from the Mosteiro de Santa Clara-a-Velha (Coimbra) stands out from the other collections, with higher SnO2 content (up to 14¿wt%), the highest Fe2O3 contents in amber glazes and a Ca-rich interface layer (mostly comprised of wollastonite, CaSiO3). Samples from Palácio Nacional de Sintra (near Lisbon) and Seville-attributed samples (from the Instituto Valencia de Don Juan) are chemically similar, except that most Sintra's samples display a K-rich glaze/ceramic interface, whereas the ones from Seville exhibit both K-rich and Ca-rich inclusions. The samples attributed to Toledo show glazes with many inclusions, contrasting with the homogeneous glazes in most Hispano-Moresque tiles. From these results, we identify differences that can be used as markers in future studies on Hispano-Moresque tiles.Peer Reviewe

Immature and Mature Collagen Crosslinks Quantification Using High-Performance Liquid Chromatography and High-Resolution Mass Spectrometry in Orbitrap

Different methodologies for collagen quantification have been described in the past. Introduction of mass spectrometry combined with high-performance liquid chromatography (HPLC) is a high-resolution tool, which has generated novel applications in biomedical research. In this study, HPLC coupled to electrospray ionization (ESI) tandem mass spectrometry (HPLC-ESI-MS/MS) was used to characterize tissue samples from AVFs done in rats. These findings helped create a protocol for identifying and quantifying components of immature and mature collagen crosslink moieties. Two different internal standards were used: epinephrine and pyridoxine. Quantification curves were drawn by means of these standards. The goal of the experiment was to achieve accurate quantification with the minimum amount of sample. Time and cost of experiment were considerably minimized. Up to date, this method has not been tested for crosslinking quantification