## 3 Results and Discussion
Furthermore, we observe elevated contents of trace elements such as CuO, SnO\({}_{2}\) and P\({}_{2}\)O\({}_{5}\) in most of the samples. [PERSON] et al., (2003) [9] have identified the levels of copper and antimony present, probably as natural impurities in raw, unrecycled, materials of HIMT glass, which are being found at mean concentrations of \(<\)0.01 wt%. The chemical composition of Vasileos Irakleiou Street, 45 samples is far from the levels proposed by [PERSON] et al., (2003) [9]. These elements occur in higher concentrations, so it should be attributed to the recycling of earlier colored glass, as these concentrations are higher than those attributable to impurities in the raw materials but too low to have any technological significance [3]. In addition, [PERSON] and [PERSON], 2016 [43] suggested that the mixture of antimony and manganese could be the result of recycling, while [PERSON], 2005 [44] reports that if glasses dated after 4 th century AD, contain low levels of antimony, it could indicate recycled glass. Recycling is probably explained by the inclusion of cullet, perhaps glass tesserae, containing high amounts of one or more of these elements, in the glass batch. In addition, among the YK1 group (Na\({}_{2}\)O \(<\) 15 wt%), there are some samples (Y300 AK, Y317B, 317 IB) that have low MnO (\(<\)0.7 wt%) and Fe\({}_{2}\)O\({}_{3}\) (\(<\)0.7 wt%) content (Figure 5). This is consistent with the amount of MnO and Fe\({}_{2}\)O\({}_{3}\) that are naturally present in the glassmaking sand. Thisatron glass group also presents an amount of CuO and PbO below 1 wt% and 0.5 wt%, respectively. Specifically, samples Y300 AK and Y317B present no manganese (MnO \(<\) 0.2 wt%), but contain antimony (Sb\({}_{2}\)O\({}_{3}\) at around 0.4 wt%). Antimony was very common as a decolorizer until the 3 rd century AD [45; 46], while from 4 th century AD manganese seems to replace antimony as the main decolorizer [43; 47], showing that the age of these samples is perhaps earlier. Manganese and iron oxide contents over 1 wt% and 1.5 wt%, respectively, are observed in the glass moils of both YK1 and YK2 groups, indicating that this MnO content may be related to its voluntary introduction in the glass batch in order to counteract the green color that would be developed due to the iron content, or to a systematic presence of MnO in the raw glass [13]. These moils also contain relatively high concentrations of CuO, SnO\({}_{2}\), and P\({}_{2}\)O\({}_{5}\), confirming the inclusion of cullet, perhaps opaque mosaic tesserae containing high quantities of one or more of these elements, in the glass batch. The glasses of the YK2 group are Sb-rich glasses that contain both MnO and Sb\({}_{2}\)O\({}_{3}\) above the sand background. The occurrence of both Sb\({}_{2}\)O\({}_{3}\) and MnO in a natron glass is generally taken as evidence of the mixing of Sb- and Mn-bearing glasses [43; 48]. Most glasses of both Vasileos Irakleiou Street, 45 groups (1,2) have contents of Sb\({}_{2}\)O\({}_{3}\) \(>\) 0.3 wt%, MnO \(>\) 0.8 wt% and TiO\({}_{2}\)\(>\) 0.2 wt%. The high TiO\({}_{2}\) contents of most of the Vasileos Irakleiou Street, 45 glasses correspond more with glasses originating from Egypt rather than in the Levant [9; 10; 41; 42]. Therefore, if we consider recycling in terms of the variations of Na\({}_{2}\)O, K\({}_{2}\)O and especially of Mn and Sb elements which are unintentionally incorporated into the batch glass during re-melting episodes [43; 49], then these components can provide an indication that recycling has occurred. However, their concentrations depend on the amount of decolored glass added to the batch glass, and to the context, e.g., longer melting durations and higher temperature. The elements that reflect the amount of time at high temperature are the K\({}_{2}\)O and P\({}_{2}\)O\({}_{5}\) concentrations.