Life histories of the dolia of Ostia: Insights into storage, use, and reinforcement in Rome's port city

Ostia, the port city of ancient Rome, played an important role in Rome's maritime commerce. The ancient port city was outfitted with massive warehouses that stored various foods necessary to supply not only the imperial capital, but also the workers living and working in Ostia. Some of these warehouses featured large ceramic storage jars known as dolia (singular dolium) that could hold over one thousand liters. Although the massive jars were useful and expensive, they cracked and were damaged easily. To extend their use, dolia were strengthened using metal, primarily lead, sometimes mixed with other metals. This paper is the first study that presents scientific evidence for the Ostian dolia's contents and reinforcements to shed light on these vessels' use and life histories in antiquity. Using gas chromatography-mass spectrometry (GC-MS) to study residues collected from eight dolia and inductively coupled plasma-mass spectrometry (ICP-MS) to study samples collected from metal additions found on four dolia from the three storerooms that are still accessible, we present evidence for how dolia of Ostia were used and maintained. Vessels were lined with pine resin and held degraded proteinaceous material, perhaps garum, at some stage during their use. They were also reinforced with lead and alloyed with other metals such as silver and tin. Compared to other dolium repairs and reinforcements, craftsmen were able to strengthen the dolia using additional, often more valuable, metals.