A new study of a 2,200-year-old Roman shipwreck reveals that ancient sailors used sophisticated organic coatings to waterproof their vessels.
Since the earliest seafaring journeys, people have needed ships that could resist saltwater, stay watertight, and endure damage from marine organisms such as worms. Despite this long history, research into non-wood materials used in ship construction received little attention until the mid-20th century, and waterproofing materials remain poorly studied today.
A new study published in Frontiers in Materials focuses on the protective coating of the Roman Republic shipwreck Ilovik–Paržine 1, which sank about 2,200 years ago off the coast of present-day Croatia. Researchers from France and Croatia analyzed the ship’s surface layers to better understand ancient waterproofing methods.
“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 Dr. Armelle Charrié, an archaeometrist at the Laboratory of Mass Spectrometry of Interactions and Systems in Strasbourg. “Studying the coatings, we found two different kinds on this vessel: one made of pine tar, also called pitch, and the other of a mixture of pine tar and beeswax. Analysis of pollen in the coating made it possible to identify the plant taxa present in the immediate environment during the construction or repairs of the ship.”
Resin and wax
Discovered in 2016, the wreck and its cargo have been examined several times. This study is the first to combine pollen data with molecular analysis to identify both the composition of the coating and the surrounding vegetation at the time it was produced and applied. The research was carried out through a collaboration between the Croatian Conservation Institute’s Department for Underwater Archaeology and the ADRIBOATS program at Aix-Marseille University in France.
“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 of these traditions, which bear witness to genuine know-how and diverse traditions.”
The team used structural, molecular, and pollen-based techniques, including mass spectrometry, to identify and measure the components of the organic mixtures.
Analysis of 10 coating samples revealed their biological origins. The molecular “fingerprint” pointed to compounds typical of pine, showing that heated conifer resin or tar, known as pitch, was the primary ingredient. One sample differed, containing a blend of beeswax and tar. This mixture – known to Greek shipbuilders as zopissa – is more flexible and easier to apply when heated.
Trapped in pitch
Because pitch is sticky, it can capture and preserve pollen from nearby plants. By studying these microscopic grains and their abundance, researchers could estimate where the materials were produced and later reapplied during repairs.
The pollen data showed a wide range of environments. These included Mediterranean and Adriatic coastal areas and inland valleys, with holly oak and pine forests, as well as matorral – a type of Mediterranean shrubland – where olive and hazel trees grow. Alder and ash indicated vegetation near rivers and shorelines, while smaller amounts of fir and beech pointed to mountainous regions typical of the northeastern Adriatic, including areas near Istria and Dalmatia.
The findings also suggest the ship received four to five separate coating applications over time. The stern and central sections shared the same material, while three distinct layers were identified at the bow. This pattern indicates repeated repairs using resources gathered from different parts of the Mediterranean.
Earlier studies of the ship’s ballast linked its construction to Brundisium, now Brindisi, on Italy’s southeastern coast. The pollen evidence supports this, suggesting some coatings were applied in that region. Other layers, however, appear to have been added along the northeastern Adriatic coast, where the wreck was eventually found.
“While it seems obvious that ships sailing long distances need repairs, it’s simply not easy to demonstrate this,” concluded Charrié. “Pollen has been very useful in identifying different coatings where the molecular profiles were identical.”
Reference: “Adhesive coatings in naval archaeology: molecular and palynological investigations on materials from the Roman Republican wreck Ilovik–Paržine 1 (Croatia)” by Armelle Charrie-Duhaut, Quentin Couillebault, Igor Miholjek and Giulia Boetto, 2 March 2026, Frontiers in Materials.
DOI: 10.3389/fmats.2026.1758862
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