The production of a glass toggle

A glass toggle was found among the ashes of a domestic hearth during the excavation of an unenclosed Iron Age settlement at Kilninian, Isle of Mull, Argyll, Scotland. The hearth was radiocarbon dated to 168 cal bc–cal ad 3 (SUERC-46765). The toggle was covered with a black residue that was stuck to its surface and it looked hastily made, using low-quality aqua cullet. Chemical analyses, using LA-ICP-MS, indicate the glass used was a natron-based glass. The trace element composition suggested the glass was produced in the east Mediterranean area using coastal sands and had subsequently been recycled. The morphological examination using extended depth of field microscopy and micro-computed tomography revealed the toggle was shaped at low temperatures using contaminated glass. The black sooty residue found on the surface of the toggle was found to extend within the toggle and was fused with the object. This could only have happened during manufacture, when the glass was still hot enough to be malleable and stick to the contamination. The uncleaned residues on the surface and the presence of the unpolished pontil scar suggest the toggle may have fallen in the hearth during manufacture and was lost to its maker. Analyses of other glass toggles found in Scotland and Ireland confirmed that natron-based glass had also been used and the toggles were made in the same way as that from Kilninian. Canmore ID 148437