Conservation and Restoration of Ceramic Amphorae from the Cape Glavina Underwater Site off Rab Island

The specialist team of conservator/restorers of the International Centre for Underwater Archaeology in Zadar received ceramic amphorae from the depot of the Open University of Rab in April of 2015. Funding for the conservation and restoration of the amphorae from Rab has been provided through the Ministry of Culture, Primorje-Gorski Kotar County and the City of Rab. The collection of fifty-two ceramic finds includes potsherds and preserved amphorae of the Lamboglia 2 type dated to the period from the second to first century BCE used primarily for the transport of wine. The amphorae were found and recovered from the sea in 1970 and have been kept since then, without prior desalination, in the storage depot of the Open University of Rab. Almost half a century later, still awaiting desalination and stored in the damp environment of the depot, we find the amphorae in very poor condition. Preliminary investigation established the condition of the received artefacts and determined the course of the conservation/restoration procedure.

The condition of the artefacts from the conservation/restoration perspective was very poor. Numerous points of damage were visible on the artefacts caused by the presence of soluble salts: crumbling of the ceramic surface, the presence of salt crystals on the surface and in the cross-section of the pottery, flaking of the ceramic walls, and the presence of many fissures. The surfaces of the amphorae were covered in calcite deposits and the remnants of marine organisms and two amphorae were entirely filled with marine sediment. The amphorae were given a preliminary brush and flowing water cleaning to remove easily removable impurities. The amphorae filed with sediment were also cleaned out in this fashion. Following cleaning, the amphorae were laid in plastic basins, already prepared and filled with tap water.

The desalination process was initiated once the amphorae had been received by submerging the labelled artefacts in basins filled with tap water. The water in the basins was replaced every four to five weeks. Each replacement of the water was preceded by a measurement of the chloride concentration, establishing the quantity of salts that had leached out of the artefacts. The desalination process was initiated on 9 April 2015 and completed on 22 August 2016 and saw the water in the basins replaced on thirteen occasions.

The desalination process was facilitated by the removal of most deposits by mechanical cleaning using scalpels, brushes/scrubbers and a pneumatic chisel. Cleaning was also expedited with a chemical procedure involving the softening of deposits by placing pads soaked with EDTA salt solution on deposits, followed by rinsing with distilled water.

The cleaned artefacts were air dried and then consolidated by immersion in a 4% solution of acrylic dispersion in distilled water. Areas where flaking and fissures were observed were reinforced by the injection of reversible archaeological pottery glue. Among the numerous sherds were a number of broken-off handles or other small broken-off sections, many of which could be paired to preserved artefacts. Some of the amphorae were highly fragmented—these fragments were sorted and arranged.

Once the precise positions of the fragments had been determined, we undertook preliminary bonding with paper tape followed by long-term bonding with pottery adhesive. Some areas, where the contact between sherds was weak, were reinforced from the inside with glass fabric coated with the above-mentioned adhesive. Larger and heavier fragments were bonded with two-component epoxy resin. The amphorae were partially or entirely integrated with finely worked alabaster plaster appropriately toned with acrylic colour.

Photographic and written documentation was created detailing the condition as received, the conducted conservation and restoration procedures, and the final post-intervention condition. Following the conservation and restoration work the fifty-two potsherds were determined to constitute eleven mostly intact amphorae, thirteen partially intact amphorae, four amphorae necks, one amphora base and three unassociated sherds. The items were successfully desalinated and assembled, ensuring their stability and prolonging their lifetime if kept in the recommended atmospheric conditions.

Martina Ćurković Madiraca