## 2 Materials and Methods  
Previously studied assemblages of archaeological glass available at the Conservation Science Laboratory of the Department of Cultural Heritage (University of Bologna-Ravenna Campus) have been selected for this study: 13 th-14 th century ampoules, unppenbecher and kropfflasche from the monastic complex of San Severo (Classe, Ravenna, Italy) [4]; 14 th-16 th century gambassini drinking vessels from the monastic complex of San Severo (Classe, Ravenna, Italy) and from the Rontana Castel (Brisighella, Ravenna, Italy) [5]; 8 th century mosaic glass tesserae from the qasr of Kihrbet al-Mafjar (Jericho, Palestine) [6]; and 8 th century mosaic glass tesserae from the Great Mosque of Damascus (Syria) [7; 8]. When other assemblages of materials from previous studies which have not been carried out by the authors are taken as examples, references are provided in the text. An Olympus S761 stereomicroscope (magnification up to 45\(\times\), Olympus Corporation, Shinjuku, Tokyo, Japan) associated with an Olympus Soft Imaging Solutions SMBH model SC100 camera (Olympus Corporation, Shinjuku, Tokyo, Japan) was used for preliminary morphological observations and documentation. For Visible Reflectance Spectrometry (VIS-RS), a MINOLTA CM-2600d portable spectrometer was used. The system is equipped with an internal integrating sphere of 56 mm diameter, in reflectance geometry d:8\({}^{\circ}\), with three Xenon pulsed lamps, and a D65 illuminant was used; calibration was performed against a BaSO4 standard plate; the spectral range is 400-700 nm, with a spectral resolution of 10 nm and the area of sight of 3 mm diameter. Spectra Magic software was employed to elaborate data; specular component excluded (SCE/0) was selected, according to the literature [9]. Microsamples were taken from either objects or diagnostic fragments for performing micromorphological, microtextural, and compositional analyses. Sections were prepared by embedding microsamples in a polyester resin then polished by using abrasive papers of decreasing grain in order to expose the embedded samples avoiding any losses. A Scanning Electron Microscope (SEM) back-scattered electron signal (BSE) was used for the inspection of the morphological features of the inclusions coupled with Energy Dispersive Spectroscopy (EDS) spot measurements to achieve a preliminary qualitative and semiquantitative elemental analysis of the inclusions themselves. Analyses were carried out on polished and carbon-coated sections. Images and EDS spectra were collected on carbon-coated crosssections, using an ESEM FEI Quanta 200, equipped with an EDAX energy dispersive spectrometer. Analyses were performed in high-vacuum using an acceleration voltage of 25 kV and an energy resolution of \(\sim\)200 eV; working distance was set at 10 mm, spot size was between four and five \(\upmu\)m.  
Micro-Raman spectra were collected by using a Bruker Senterra dispersive Raman spectrometer equipped with an integrated Olympus BX40 microscope. A 785 nm He-Ne laser was employed, in the 300-3500 cm\({}^{-1}\) region. Analytical measurements were performed with a 50\(\times\) long working distance objective, operating at a power of 10 mW (red and blue samples) or 25 mW (yellow and green samples) with a spectral resolution of 3.5 cm\({}^{-1}\). Raman measurements were performed on polished sections after carbon-coating removal. X-ray Powdered Diffractometry (XRPD) analyses were performed on finely powdered samples manually pressed on a Ag sample holder in a Rigaku Miniflex diffractometer employing CuK\(\alpha_{1}\) radiation in the range 20: 4\({}^{\circ}\)-64\({}^{\circ}\), \(\theta\) scan speed: 1\({}^{\circ}\)min\({}^{-1}\). To determine the bulk chemistry of all samples under study, Electron Probe Microsanalysis (EPMA) was performed on polished and carbon-coated sections.