Lead sheathing of ship hulls in the Roman period: Archaeometallurgical characterisation

An archaeometallurgical analysis of samples of lead sheathing from five ships of the Roman period was carried out in order to determine their composition and microstructure, and to obtain a better understanding of their manufacturing processes. The examinations included optical microscopy of metallographic cross-sections, microhardness tests, scanning electron microscopy, including energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. The results show that the samples were all composed of lead covered with an oxide layer. The sheet thicknesses, microhardness values and microhardness distribution, as well as the grain size distribution, led to the conclusion that all of the sheets were produced by the same technology, using hammering, and were probably used for the same purpose. The presence of antimony was observed in the sample from the Roman ship from Caesarea, which may hint at an Italian (Sardinian) origin of the material, and perhaps of the ship.

Research Highlights
► During the Roman period ship hulls were sheathed with lead.
► Five samples have been analysed for their characteristics and manufacturing process.
► The process was cold-working (strain-hardening) using hammering.
► The lead was open-casted on a flat stone, and later hammered at room temperature.
► Antimony in the Caesarea shipwreck may indicate an Italian origin of construction.