*3.1. Understanding Archaeological Context: The First Step toward a Tailored Selection of Materials*

The most recurring questions related to the study of archaeological materials are aimed at understanding whether a local production can be identified. This issue is of a particular relevance for glass, where the very sporadic occurrence of furnace remains makes it extremely challenging to map the production sites and distinguish them from the working sites. If the context where materials have been unearthed shows evidence of a production/working activity of glass (i.e., furnace remains, production waste, and tools), the selection of the assemblage to be investigated is generally aimed to characterise all these indicators. Therefore, the choice to carry out archaeometric analyses on materials that can be typologically heterogeneous (such as production indicators, scraps, and finished objects) is justified by the need to identify raw materials used in glassmaking. An example is, in this regard, the ancient port of Classe (Ravenna, Italy), one of the most important trade centres between the 5th and 8th centuries CE in the Northern Adriatic area. Archaeological excavations identified the main context for glassworking inside one of the warehouses built at the beginning of the 5th century CE, where a small circular kiln had been unearthed; around the kiln, a massive amount of glass fragments and glassworking waste (973 finds) was brought to light in 2001 [14]. Results from archaeometric analyses demonstrated that, in the 5th century CE, the secondary glass workshop in Classe was dedicated to the shaping of vessels starting from raw glass chunks and, possibly, cullets. Evidence of glass remelting and glassblowing were found, while no evidence of primary production was uncovered [15]. Moreover, comparisons between Classe and Aquileia, the two most important Late Antique archaeological sites of Northeastern Italy, were undertaken to shed light on the role of the Northern Adriatic area in glass production, trade, and consumption. The comparison showed that, unlike Classe, correlations did not exist in Aquileia between specific types of objects and the compositions of glass; this data has further strengthened the hypothesis of a local shaping of specific objects at Classe [16].

An analogous approach in the selection of materials to be studied can be applied to cargos from shipwrecks. The case of the wreck of the Iulia Felix ship, which sank in the 2nd century CE off the coast of Grado (Friuli-Venezia Giulia, Italy) is, in this sense, thorough. The archaeological and archaeometric study of the assemblage of glass materials was performed on cullets and finished objects to achieve data on colourless and coloured Roman glass production technology. The strong evidence of compositional variability among the Iulia Felix assemblage strengthened the hypothesis of a dispersed production model for Roman glassware and the common practice of recycling in Roman ages, especially for daily-use vessels [17,18].

If archaeological glass is found at multilayered contexts and/or where there is no univocal evidence of local production, the approach to the selection of materials to be studied needs to be different. Multilayered contexts are particularly challenging to be approached: inhabited for more or less extended periods, they generally are urban, monastic, and/or residential sites, where structures that can be interpreted as small kilns, though without sound evidence of glass production (i.e., no production/processing indicators recovered), can also be found. When these contexts are faced, an archaeometric study of numerically consistent sets of fragments (without paying due attention to the multilayered structure of

the site and often comparing data obtained from the analysis of fragments pertaining to different objects and chronological frames) can rarely result in a meaningful and exhaustive scenario. The result is often a multiplicity of hypotheses regarding the import of objects from other sites and, when no comparisons can be found with other sites, the risk is to hypothesise local productions without sound archaeological evidence.

Recent studies have highlighted the potential associated with adopting a synergistic transdisciplinary approach when working on multilayered contexts. The starting point is represented by an in-depth tailored archaeological study of the assemblage functional to identify distinctive shapes and their chronology. The results obtained by chronotypological study of the objects can, in fact, outline different scenarios to assess; the most common are those characterised by a) specific groups of objects with the same chronology; (b) a greater statistical incidence of a specific distinctive shape (or a few of them). Depending on whether the chronotypological study of the finds identifies one or the other scenario, key issues to which the archaeometric analyses will be called to contribute will be evaluated. An exhaustive example of the approach centred on the study of specific types of objects falling within the same chronological frame is provided by Sedlackova and colleagues [19]. The study aimed to investigate the production and import of glass objects in Bratislava involving finds of tableware and window glass. The preliminary archaeological study allowed the attribution of the finds to three main timeframes verified by the occurrence of distinctive shapes and decorative features: 13th, late 13th–14th and mid-15th century CE. The subsequent archaeometric investigations made it possible, for each of the examined periods, to ascertain the composition of the glass and to establish comparisons with chronologically compatible Central Europe productions shedding light on commercial and political orientations. The study is an example of how informative data can also be obtained by working on a small number of fragments, as long as well contextualised from a chronotypological perspective to set up comparison with the same types of objects found in other geographical areas.

The same methodological approach has been applied to a first selection of materials from the monastic complex of San Severo in Classe (Ravenna, Italy) [4]. The chronotypological study of the material identified the occurrence of three particular types of glass objects, although not present in statistically high numbers: ampoules, nuppenbecher, and kropfflasche, dated to the 13th–16th century CE. The close similarities, in terms of chemical features, between these objects from San Severo and comparable finds from Czech Republic, further strengthened the hypothesis of commercial contact between Central Europe and Italy in the Middle Ages. The scope of both studies, focused on a few distinctive shapes, was to trace, through an interrelation between chronotypological and archaeometric study, contacts between two geographically distant areas, united by the occurrence of the same types of glass objects. The monastic complex of San Severo can be taken as an example of another approach applicable to archaeological glass, based on the study of one (or a few) statistically relevant shape(s). This is the case of the daily-use drinking glass beaker known as gambassino [5]. Recently published research aimed at deepening the historical, archaeological, and compositional knowledge between the variants of this object, found in two contemporary sites located at a distance of about 50 km from each other: the monastery of San Severo and the Rontana castle (Brisighella, Ravenna, Italy). For both sites, the gambassino was the shape with the greatest statistical impact, accounting for over 70% of the entire assemblage of unearthed glass materials [14]. Moving from a local scale, the study then expanded to regional and transregional comparisons involving central-northern Italy and the Balkan side of the Adriatic Sea. Thanks to an interrelation among archaeological, historical, and archaeometric data, evidence has been underpinned for the movement of finished objects, raw materials, and artisans in the considered timeframe: the displacement of artisans and the circulation of raw materials, the recurrence of this beaker in numerous excavation contexts in the northern Adriatic area, as well as the identification of compositional groups different from each other but overlapping among assemblages, has led to the

hypothesis of a "widespread production" model of the common drinking beaker known as gambassino.

The aforementioned studies stand as examples of the great variety of approaches applicable to the study of archaeological glass. The selection of one or the other approach cannot be separated from the in-depth knowledge of the archaeological context, paying particular attention to the type of settlement (i.e., urban, rural, residential, or monastic) and to its continuity of life across time. Being aware of the context is, thus, the first step to be taken. The next step is the in-depth study of the finds, of the way they are linked to the chronology of the site, and of their possible connections with other contexts. All these elements contribute to the definition of the questions underlying the selection of the samples to undergo archaeometric analyses, so that they can provide suitable data to support hypotheses of production and/or provenance of the artefacts under study.
