The ancient glass production of the Medieval Val Gargassa glasshouse: Fe and Mn XANES study Simona Quartieri a, * , Maria Pia Riccardi b,c , Bruno Messiga b,c , Federico Boscherini d a Dipartimento di Scienze della Terra, Universita ` di Messina, Salita Sperone 31, 98166 S. Agata di Messina, Italy b Dipartimento di Scienze della Terra, Universita ` di Pavia, via Ferrata 1, 27100 Pavia, Italy c CISRIC, Centro Interdipartimentale di Studi e di Ricerche per la Conservazione dei Beni Culturali, Universita ` degli Studi di Pavia, via Ferrata 1, 27100 Pavia, Italy d Dipartimento di Fisica, Universita’ di Bologna, and Istituto Nazionale per la Fisica della Materia, viale Berti Pichat 6/2, 40127 Bologna, Italy Received 18 October 2004; received in revised form 15 June 2005 Available online 15 August 2005 Abstract Glass finds from the Medieval Val Gargassa glasshouse (Genova, Italy) were investigated by chemical and spectroscopic tech- niques (colorimetric analysis and X-ray absorption spectroscopy) with the aim to obtain information on the ancient glass production technique. Sampling covers all the typologies of archaeological findings unearthed by the digging, as well as fragments of finished glass-wares. The results indicated that the samples are soda-lime based glasses. The color variability was exerted by the glassmakers by both controlling the kiln atmosphere and/or adding MnO 2 as decoloring agent. In both cases, the Fe 2+ /Fe 3+ ratio was modified at a specific step of the production cycle. Ó 2005 Elsevier B.V. All rights reserved. 1. Introduction and archaeological context Even in ancient times, glass production required ad- vanced technology in terms of selection of raw materials, and also firing had to reach good efficiency levels. Dur- ing the production cycle, several operations, made by glassmakers, produced waste that, discarded by the pro- duction cycle, became part of the archaeological sedi- ment. In glass archaeology, the so-called Ôproduction indicatorsÕ are those remains which testify specific oper- ations carried out during the productive cycle, implying fritting, melting, flashing (mixing), boiling and working [1,2]. In other words, when analyzed, they allow us to reconstruct the processes and technological expedients used in the past to produce glass. A great part of Liguria and Southern Piedmont rep- resents an important Italian area where several glass- houses produced worked glass in medieval times. The location of these pre-industrial plants along the North- ern slope of the Apennines was an unavoidable choice determined by the need of combustible, and the name of Ôforest glasshousesÕ is, in this contest, truly appropri- ate, because the presence of woodlands. The glasshouse here investigated is located near a meander along the upper course of Gargassa River. Later on, the glass- house was partially replaced by a farmhouse during the 19th-century. The Val Gargassa glasshouse (Genova, Italy) was active in medieval times (about XIII–XVI century AD). The excavation gave back more than 3000 findings that allowed characterizing the whole productive cycle. The color exhibited by glasses can be due to the oxi- dation state and the electronic configuration of the metal ions in them [3–5]. These are usually elements belonging to the transition row of the periodic table, 0022-3093/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2005.06.046 * Corresponding author. Tel.: +39 0906 765096; fax: +39 0903 92333. E-mail address: simonaq@unimo.it (S. Quartieri). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 351 (2005) 3013–3022