Spontaneous glass fracture in archaeological artifact: The impact of fire

This study investigates the state of preservation of colorless glass bowls from the 5th century BCE found at the archaeological site Casas del Turuñuelo (Guareña, Spain). Despite having identical chemical compositions, the bowls are in varying states of preservation. Analytical techniques including SEM-EDS, Vickers hardness testing, polariscope examination, and hot-stage microscopy reveal that two bowls remain largely intact with common alteration layers, while another is shattered and has different mechanical properties. The results suggest that the exposure to ceremonial fires induced internal stresses induced internal stresses that led to spontaneous fracturing. Subsequent burial conditions, including groundwater fluctuations and soil chemistry, favored fissure propagation and alteration.