Traces of pyrolusite in a chunk of raw glass, the result of a failure to produce colorless glass at Sagalassos |
Photos courtesy Sagalassos Archaeological Research Project. Click on images to enlarge. |
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by Marc Waelkens |
Glass Studies: Introduction
After a preliminary study last season, a systematic and comprehensive analysis of the excavated glass was initiated this year by Veerle Lauwers and Patrick Degryse (respectively KULeuven and Expertise Center for Bio- and Geoarchaeological Sciences and Image Processing, KULeuven: www.archscience.be). They hope to shed new light on the different typological versus chronological contexts in order to compile an internal chronological seriation of the glass, independent of the chronology based on ceramics. To further study the raw materials used for glass production, they have taken samples of glass chunks and production waste for chemical and isotopic analysis. The origin or raw glass at Sagalassos needs to be pinpointed, although import of HIMT glass from Egypt and local recycling can be proven. One special find this week was a chunk of raw glass, showing an unhomogeneous color, probably as a result of an insufficient or failed addition of decolorant in a reduced furnace atmosphere (e.g. manganese in the form of the mineral pyrolusite). After chemical analysis, this piece may prove to be crucial for the investigation of local glass discoloring at Sagalassos.
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