## 1 Introduction  
Glass production in ancient times required three basic components. The main material was a network former (silica source), usually quartz-limestone sand or quartz pebbles, the second was a flux, for example natron (soda-lime-silica glass), or soda ash from halophytic plants (such as Salsola kali or Salicornia), or potash ash from trees (oak, beech, birch), and the third was a stabilizer, usually limestone or sea shells (which sometimes the sand already contained) [1]. The natron type glass (soda-lime-silica glass), which is characterized by the low magnesium and potassium content, used to be the dominant type of glass from the 10 th century B.C. until almost the 9 th century A.D. [2, 3, 4, 5].  
During the Roman and early Byzantine period, within natron type glasses, two new types of glass were making their way to the glass industry. The first type is called HIMT (High Iron Manganese and Titanium) glass, because of the high contents of these three elements [6], and it was possibly produced using a silica source originating from Egypt [7, 8, 9, 10]. The main reason the HIMT type glass began to become in demand was probably because of its lower sand quality, which could suggest a lower price [11, 12]. The second type is called Levantine I glass and its silica source came from the Syro-Palestinian coast [11, 13, 14, 15].  
In the same period, the production of glass was intense, thus there was an imperative need for large quantities of raw materials and production sites. According to [PERSON] [16], the production sites were either primary or secondary. Primary workshops produced raw glass by processing the raw materials (i.e., sand and natron). Afterwards, this raw glass was broken into chunks and then the chunks were transferred to secondary workshops where glass artefacts were made [13; 14; 17; 18]. This production theory is suggested by [PERSON] in his Naturalis Historia [16] and by several archaeological excavations on the Pyro-Palestinian coast [12; 13; 19], in Egypt [20; 21], Greece [22; 23], France and the United Kingdom [24; 25].  
The glass imported in Greece (mainly from the 1 st to 6 th century A.D.) was coming from primary workshops in Egypt and Near East sites and was fused locally to produce artefacts. Nonetheless, in Thessaloniki during the Late Roman period, the manufacture of glass artefacts was verified by [PERSON] 2011 [26], and it also seems that in Northern Greece (Macedonia) the glass products were plentiful [27]. The existence of different primary and secondary workshops makes distinguishing between local and foreign production of the glasses difficult, thus it is very important to chemically analyze the glass as this can give us information not only about their components but also on the production technologies and consequently on the origin of raw materials [9; 23; 25; 28; 29; 30; 31; 32; 33; 34; 35]. Such information can also provide us with economic, cultural and social connections between the different geo-political Eastern Mediterranean regions during antiquity.  
Therefore, the existence in Greece of local production centers of glasses, as well as the trade of raw materials and glass artefacts which were probably produced in Near-East or Middle-East countries, draws attention to the importance of trying to identify the origin of Late Antique glass objects produced in Greece, to distinguish the different raw materials and fluxes used for glass production, and to define the production technologies.