A combined molecular and pollen analysis of waterproofing residues from a 2,200-year-old Roman shipwreck has revealed distinct coating batches, suggesting the vessel underwent successive repairs around the Adriatic Sea.
The study examined organic hull coatings from the Ilovik–Paržine 1 wreck, a Roman Republican vessel discovered off Ilovik Island, Croatia. Earlier ballast analysis suggested the vessel was built near Brundisium, now Brindisi, while the new work investigated where the coatings were produced or applied.
“In archaeology little attention is paid to organic waterproofing materials. Yet they are essential for navigation at sea or on rivers and are true witnesses of past naval technologies,” said first author Armelle Charrié in a press release.
The researchers analyzed 10 coating samples from different areas of the wreck. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) provided structural information on organic functional groups, while gas chromatography-mass spectrometry (GC-MS) was employed to identify diagnostic molecular markers. Pollen grains trapped in the coatings were also analyzed to reconstruct the vegetation present when the materials were produced or applied.
The molecular profiles showed that all analyzed coatings were based on a conifer-derived material, consistent with heated resin or wood tar known as pitch. Diagnostic diterpene markers, including dehydroabietic acid, pointed to heat-treated Pinaceae material, although alteration had affected the archaeological samples. One sample, PA 101, also contained beeswax markers, indicating a pitch–beeswax mixture comparable to zopissa, a coating described in ancient sources.
The pollen results added a geographical layer that molecular chemistry alone could not provide. Statistical analysis suggested four to five distinct coating batches across the wreck, with more homogeneous coatings at the stern and central sections and several distinct batches at the bow. The pollen assemblages indicated Mediterranean coastal and valley environments, with some samples consistent with the Brundisium area and others closer to the north-eastern Adriatic coast.
The authors suggest that these differences may reflect successive repairs using materials sourced or applied in different places during the ship’s working life. More broadly, the study shows how waterproofing residues can preserve evidence of local shipbuilding and repair traditions that are otherwise difficult to reconstruct from timber alone.
“Some regions throughout the Adriatic have particular characteristics that led local populations to develop a specific shipbuilding style,” said Charrié. “Only studies like ours offer an overview into these traditions which bear witness to genuine know-how and diverse traditions.”
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