Glass and metal analyses of gold leaf tesserae from 1st to 9th century mosaics. A contribution to technological and chronological knowledgE

Glass and metal analyses of gold leaf tesserae from 1st to 9th century mosaics. A contribution to technological and chronological knowledg

La produzione di tessere musive a Milano tra IV e V sec.? Un\u2019indagine archeologico-archeometrica

The paper aims to test the hypothesis \u2013 known in literature \u2013 of the existence of a workshop producing glass tesserae in Milan. The topic is addressed by means of an interdisciplinary approach, but with a fundamental role played by archaeometric analyses performed on the sites of San Lorenzo (late 4th-early 5th c.) and San Giovanni alle Fonti (late 5th-early 6th c.). The analyses show how the supply of raw materials and the colouring and opacifying techniques change between the late 4th and the early 6th century. The tesserae from San Lorenzo appear to have been imported, while most of those from San Giovanni \u2013 opacified with a tin-based procedure, not recorded so far in any other analysed mosaic glass from Italy \u2013 could perhaps have been produced locally

Produrre tessere d\u2019oro: bordi di piastra, ricettari, analisi archeometriche

In questo articolo si intende presentare un progetto in corso che ha lo scopo di indagare le tecniche di fabbricazione delle tessere a foglia d\u2019oro di et\ue0 tardo antica, la cui problematicit\ue0 \ue8 nota in letteratura. Viene innanzitutto affrontato uno studio comparato delle procedure tecniche presentate da ricettari medievali e rinascimentali e ricostruibili dai bordi di piastra allo scopo di riconoscere nei reperti le tracce materiali del processo seguito. In secondo luogo vengono determinati i materiali impiegati attraverso analisi archeometriche di tessere proveniente da diversi siti (Aquileia, Milano, Roma, Ravenna, Monte Nebo). Dalle analisi risulta che le foglie d\u2019oro hanno un titolo di fino comparabile solo a quello delle monete auree. Questo permette di ipotizzare che la produzione fosse legata alla zecca aurea. L\u2019ipotesi \ue8 confermata da indicazioni presenti nei ricettari e dalle dinamiche relative alla circolazione dell\u2019oro in et\ue0 tardo antica. Le analisi del vetro di supporto e della cartellina permettono di comprendere relazioni commerciali, individuando possibili provenienze dei vetri primari (in base ai gruppi noti in letteratura) e tecniche di decolorazione. Ci si interroga infine sulla scelta di tessere diverse, in vetro trasparente incolore e di tonalit\ue0 giallo-verde, all\u2019interno di uno stesso cantiere

Scientific Analyses of Glasses from Late Antique and Early Medieval Archaeological Sites in Northern Italy

Recent finds of glass fragments at archaeological sites in northern Italy have shed new light on the history of Italian glass technology between the fourth and 13th centuries. Some fragments were examined by electron probe microanalysis

SEM-EDS Analysis of ancient gold leaf glass mosaic tesserae. A contribution to the dating of materials

Metal leaf (gold, silver or their alloys) glass tesserae began to be used in wall mosaics in the first century AD (the first examples are in Rome) and their use has been uninterrupted up to day. The metal leaf could be obtained from circulating coins, jewellery or refining. According to various techniques that have changed over the centuries, the leaf was hot fixed between two glass layers. From an archaeological point of view, it is interesting to know when and where these tesserae were made, if they were new made or if they were reused tesserae recovered from earlier dismantled mosaics. The determination of the glass composition of the tesserae is not of great help in this connection, for the same kind of glass was used over long periods. Available information is still scanter for glasses produced between the 1st to 8th centuries when the batch of raw materials (a natural soda called natron and a silica-lime sand) was melted in large tank furnaces and chunks of raw glass were transported all over the Mediterranean to be remelted and shaped into manufacts in small pot furnaces. The SEM-EDS analysis is proposed in this study as a useful tool to investigate the composition of both the glass and the gold alloy in leaf tesserae from mosaics of the 1st - 9th centuries. The comparison of the composition of the gold leaf of the tesserae with that of circulating gold coins (for which an important analytical data base is available), adds further information to the glass analysis, allowing us to improve the dating of the tesserae and increase the knowledge that may result from scientific analyses. The results demonstrate that good quantitative analyses of the metal leaf can be performed and that metal leaves made of pure gold or gold-silver alloys were used

Glass mosaic tesserae from the 5th-6th century baptistery of San Giovanni alle Fonti, Milan, Italy. Analytical investigations

L\u2019articolo si propone di analizzare i resti della documentazione musiva del battistero di San Giovanni alle Fonti, probabilmente commissionata dal vescovo Lorenzo. L\u2019analisi archeometrica delle tessere, effettuata da Marco Verit\ue0, permette inoltre di interrogarsi sulle complesse logiche di produzione e di approvvigionamento dei materiali. Questo consente di valutare meglio il livello della committenza e l\u2019entit\ue0 dell\u2019impresa necessaria per realizzare un ciclo musivo

SEM-EDS ANALYSIS OF ANCIENT GOLD LEAF GLASS MOSAIC TESSERAE

The SEM-EDS analysis is proposed in this study as a useful tool to investigate the composition of both the glass and the gold alloy in leaf tesserae from mosaics of the 1st - 9th centuries. The comparison of the composition of the gold leaf of the tesserae with that of circulating gold coins (for which an important analytical data base is available), adds further information to the glass analysis, allowing us to improve the dating of the tesserae and increase the knowledge that may result from scientific analyses. The results demonstrate that good quantitative analyses of the metal leaf can be performed and that metal leaves made of pure gold or gold-silver alloys were used