Glass from the 11th-13th century medieval castle of San Giuliano (Lazio Province, Central Italy)

Compositional analysis of glass from the medieval castle of San Giuliano (Lazio, Italy), occupied from approx-imately CE 1050-1250, sheds light on the financial wherewithal and integration of the castle's elite inhabitants into wider economic networks. Portable X-ray fluorescence (pXRF) of 261 shards was used to select 32 for further analysis using wavelength dispersive electron microprobe analysis (EMPA-WDS). This compositional analysis documents the pervasive recycling of earlier glass cullet, some of which pre-dates the 4th century CE. Around 20% of the sample comprised primarily plant ash glass, evidencing the penetration of plant-ash glasses into inland sites on the western central Italian peninsula. Almost 60% of the shards were an intermediate glass combining more recent plant ash glasses with recycled natron-based glass cullet derived from the Roman and Early Medieval periods. Compared to glass assemblages from contemporaneous sites, the levels of both recycled and intermediate glasses are quite high, with a concurrent incidence of trace elements that further precluded the manufacture of perfectly translucent glass vessels. This suggests that while the residents of the castle desired glass as a symbol of prestige, they may not have had the economic resources to obtain glass of the highest quality.