Chemical analysis of 17th century Millefiori glasses excavated in the Monastery of Sta. Clara-a-Velha, Portugal: comparison with Venetian and façon-de-Venise production (original) (raw)
Related papers
Provenance studies on façon-de-Venise glass excavated in Portugal
2016
In this study façon-de-Venise glass objects from several Portuguese archaeological sites were studied aiming at characterising their chemical composition, discussing the raw materials and possible provenance. These objects were found during four archaeological excavations performed in Portugal (at Santa Clara-a-Velha Monastery (SCV) in Coimbra, São João de Tarouca Monastery in Lamego (SJT), Miguel Fernandes Square in Beja (PMF) and at the courtyard of the University of Coimbra (CPU)). Most fragments are dated to the 17th century, with only two objects being dated between the 14th and 15th centuries. These last two fragments, due to chronological reasons, can't be attributed to a façon de Venise production, but were included in this study for comparison. The glass compositionwas characterised bymeans of particle induced X-ray emission (μ-PIXE), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and UV–Vis reflectance spectroscopy. All thirty-one objects are composed by soda–lime–silica glass and the use of coastal plants as raw materials is suggested by the contents of MgO, K2O, P2O5 and chlorine. The observed greyish/bluish glass hue was also investigated and UV–Vis analysis allowed one to identify Co and Fe as the cations responsible for that hue. Through the analysis of silica trace elements and of the flux agents it was possible to associate four objects, from the Santa Clara-a-Velha Monastery assemblage, to Venetian production (three objects of cristallo and one object of vitrum blanchum) and to identify two other distinct production lines. One group comprising fragments from São João de TaroucaMonastery, presented medium alumina contents, differing from known façon-de-Venise production centres. The other group includes most fragments from Miguel Fernandes Square assemblage and has high alumina values, which, once again, is not consistent with any of the known façon-de-Venise production centres. For these reasons, the existence of new façon-de-Venise production centres is proposed.
New insights into 17th and 18th century glass from Portugal: study and preservation
2016
Early Modern glass from the Iberian Peninsula has-so far-seldom been investigated. The project, combining chemical analysis with a stylistic approach, and focusing on composition and technology, aims to characterise glass objects circulating in the national territory, in an attempt to identify their origins and to eventually bring to light a Portuguese centre of glass production. The chemical composition of more than 200 glass fragments was determined by means of µ-PIXE down to a level of tens of µg/g. The results obtained allowed one to select some objects to further extend the analysis to the trace and rare earth elements (REE) down to the ng/g level, through the use of LA-ICP-MS. Glass colours and natural hues were studied by means of UV-Vis reflectance spectroscopy and, when necessary, enamels were studied by means of µ-EDXRF and µ-Raman microscopy. From all the objects analysed, it was possible to conclude that the great majority of the glass dating upto the 17 th century, is of a soda-lime-silica type, which indicates a Mediterranean tradition. Venetian or façon-de-Venise shapes were identified, and for some of them a Venetian provenance was confirmed. For other façon-de-Venise shapes, the composition presented differences that led to the conclusion that new façon-de-Venise production centres could be recognised. From the only assemblage containing glass fragments dated to the medieval period, it was possible to attest the presence of Venetian glass in the Portuguese territory from at least the 14 th century. Additional objects showed particular compositional features, such as high and very high alumina contents for instance, that, as far as it is known, do not match up with any of the known glass production centres in Europe. Allying the stylistic characteristics with the glass chemical composition, allowed one to identify some objects possibly belonging to a Portuguese production. Several glass fragments belonging to wine bottles were retrieved from archaeological excavations in Lisbon and were chemically characterised. The chemical analysis revealed an HLLA composition for all of them. For some of these fragments it was possible to propose an English provenance. Besides the chemical characterisation, a systematic analysis of the bottle shape was proposed since the shape can be an important factor in determining its chronology. A small percentage of the fragments were identified chemically as having mixed-alkali compositions, potassium-rich glass, and lead glass compositions. The latter two chemical formulations were found among the assemblages from Lisbon and the objects with these compositions were dated to the 18 th viii century. These constitute evidence that Portugal followed European tendencies in their glass and its compositions. This is the first systematic chemical characterisation of Early Modern glass circulating in Portugal, providing new insights into trade between Portugal and its trade allies. As a part of the study, and to prolong the survival of these glass assemblages, simple and low cost optical sensors were developed for the in situ detection of the organic pollutant formic acid, which is emitted by materials usually used in storage and in the display of glass. The detection of the presence of this acid can play an important role in the preservation of this valuable heritage; glass.
2018
A set of 46 fragments decorated with the filigree technique were unearthed in Lisbon and dated to the 16th and 17th centuries. The aim of this investigation is to combine the archaeometric study of the glass together with the technology used to produce these beautiful and luxury items, in order to discuss their probable provenance. The glass composition was characterized using laser ablation inductively coupled plasma mass spectrometry (LA- ICP-MS). It was possible to identify genuine Venetian glass but it was also possible to find glass compositions that do not relate with any of the compositions from known façon-de-Venice glass production centers.
Renaissance Millefiori Glass: The Portuguese Case Study AUTHORS
2019
The Italian word millefiori literally means “thousand flowers” and encompasses glass objects whose surface is decorated with multi-coloured slices of glass canes, usually having concentric patterns. The use of canes is first related to mosaic glass technique, one of the most ancient glass working techniques. During the Renaissance, Venetian glassmakers rediscovered and developed the millefiori technique adapting it to the glassblowing process by rolling a bubble of molten glass over glass cane slices to pick them up. In this work, the term millefiori would only be used to describe the glassware decorated by this process. This type of glass objects seems to be rare and only few specimens belong to museums and private collections or have been documented in archaeological excavations spread throughout Europe. However, more than one hundred and fifty glass fragments with a wide use of different type of patterns were found in five Portuguese archaeological sites. Given that the documentation is one phase of paramount importance to preserve and give value to the cultural heritage, a survey that combine a morphological observation with the chemical characterisation has been began, to open our knowledge about the history of this glass. Stereoscopy and optical microscopy were used for the morphological study. The chemical characterization was performed by the following techniques: particle induced X-ray emission (µ-PIXE) mapping to visualize how the oxides are distributed through the different layers and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to obtain the major, minor, trace and rare earth elements composition. To observe, in cross-section, the morphology of the stratigraphic layers, opacifying agents and inclusions, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) was performed. Raman spectroscopy was used to study the opacifiers, and UV-Visible reflectance spectroscopy to assess the chromophores present in the glass. The work developed so far allowed us to understand that when comparing the different decoration patterns present in the Portuguese assemblages with the literature, new decoration motifs were found. In addition, it was possible to determine a large variation in the materials, colours, and manufacture quality.
I s t I t u t o v e n e t o d I s c I e n z e , l e t t e r e e d a r t I at t I tomo clxxIII classe dI scIenze fIsIche, matematIche e naturalI fascicolo I clxxVII anno accademIco
Journal of Analytical Atomic Spectrometry, 2001
In this paper, the differences and similarities in chemical composition between façon-de-Venise glass excavated in Antwerp and two types of Venetian glass, both from the sixteenth and seventeenth centuries, are documented. On the basis of typological criteria alone it is not possible to distinguish imported Venetian glass from locally produced glass. For this purpose, the major element composition of Antwerp and Venetian glass was studied with EPXMA (electron probe X-ray microanalysis) and, in a second phase, these objects were also analysed for their trace element content by means of SR-XRF (synchrotron radiation induced X-ray fluorescence analysis) and LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry). The largest group of Antwerp objects has a composition that significantly differs from truly Venetian compositions, pointing to an important local production. However, a few objects were found that have a major composition very similar to Venetian Cristallo and a larger group corresponds to the Venetian Vitrum Blanchum composition. In order to be able to make a more clear distinction between the Antwerp Cristallo and Venetian Cristallo glass types, to verify that indeed the Antwerp and Venetian Vitrum Blanchum compositions are identical and to understand better the causes of the compositional differences among the groups, the concentrations of a number of trace elements, possibly providing clues on the raw materials, were determined.
Microchemical Journal, 2023
Accurate microchemical characterisation was performed on a 4th-12th-century repertoire of coloured and colourless glass samples found in the archaeological excavation of Jesolo (ancient Equilus, northern Italy). The research aimed to improve the state-of-the-art knowledge of early medieval glass, through the characterisation of a stratigraphically very well-dated and homogeneous glass collection, further representing a unicum in the area of the western upper Adriatic. A representative sampleset of sixty-seven glass finds -including vessels, windows, tesserae and blocks of raw glass- was investigated by electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). All samples are classified as soda-lime-silica glass made of impure sands and natron. In most cases, glass colour is imparted by iron naturally present in the sands, often counteracted by varying levels of manganese. The collection also includes numerous Co- and Cu-coloured glass. Colourless glass is Mn-decoloured or, to a lesser extent, Mn/Sb-decoloured. The proportion between fresh and recycled glass is almost equal. The provenance investigation has established that while Levantine imports are numerically limited, most materials can be traced back to the Egyptian area. Among the twelve samples assigned to the Levantine area, both Jalame-type and Apollonia-type glass has been identified in an almost equal percentage. Among Egyptian glass, a consistent group of 22 samples has been straightforwardly assigned to the HIMTa and, to a lesser extent, HIMTb groups. Both group 2.1 and 3.2 are clearly attested in almost equal amounts but individually less frequent than HIMT.
Heritage, 2024
One of the most recognized decorations of the pick-up technique is the millefiori glass, which has been commonly attributed to Venetian production. However, Portugal is the country where the largest known assemblage of this type of glass artefact has been studied and published. In this work, two important archeological contexts were selected: (1) Santa Clara-a-Velha monastery (SCV) and (2) São João de Tarouca monastery (SJT). The fragments selection was made based on the diversity of decorative motifs, colors, and original forms that has been associated with Portuguese production. The compositional characterization was conducted by performing micro-particle-induced X-ray emission (µ-PIXE) mapping, which facilitated the visualization of the distribution of different oxides across the different glass layers and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to obtain the major, minor, and trace elements composition, including rare earth elements (REEs) to determine which kind of raw materials were used. Additionally, µ-Raman spectroscopy was employed to investigate the opacifiers, while UV–Visible spectroscopy was used to study which chromophores are presented in the glass samples. All the analyzed glass layers can be considered to be of a soda–lime–silica type, and four different geological patterns (from GP1 to GP4) were detected and reported. This result can indicate that these objects were made by using silica sources taken from four different geological settings. Interestingly, the GP3 represents about 41% of the analyzed glass fragments and is compatible with the pattern detected in some production wastes found in two different archeological contexts located in Lisbon, which reinforces the veracity of the theory that this GP can be attributed to a Portuguese production. On the other hand, GP1 was probably attributed Granada provenance.