Off the Croatian island of Ilovik, a Roman cargo ship has been sitting on the Adriatic seabed for more than two thousand years. Now, a team of researchers led by marine archaeologist Irena Radić Rossi of the University of Zadar has pulled 10 coating samples from its hull and run them through a battery of chemical tests. What they found tells a surprisingly hands-on story: the crew, or the dockyard workers who serviced the vessel, waterproofed it with pine tar and, during at least some repair sessions, blended that tar with beeswax to create a second, distinct sealant recipe.
The results, published in May 2026 in the peer-reviewed journal Frontiers in Materials, offer some of the clearest chemical evidence yet that ancient Mediterranean sailors did not just build ships and hope for the best. They maintained them, adapted their materials, and made deliberate choices about which formula to slather on the planks during each round of repairs. As the study’s authors write, the presence of two chemically distinct recipes in separate layers “indicates multiple maintenance events over the vessel’s operational life.”
Two recipes, one hull
The wreck, cataloged as Ilovik-Paržine 1, dates to the Roman Republican period. To decode its coatings, the research team combined three analytical techniques: Fourier-transform infrared spectroscopy (FTIR), gas chromatography/mass spectrometry (GC/MS), and palynology, the study of pollen grains trapped inside the dried sealant. Each method attacks the problem from a different angle. FTIR and GC/MS identify molecular signatures, picking out specific diterpenoids linked to pine resin and long-chain esters characteristic of beeswax. Palynology narrows down the botanical source of the raw materials by cataloging the pollen species embedded in the coating matrix.
Together, the three methods confirmed that some hull sections carried a straightforward pine tar or pitch layer, while others bore a blend of pine tar and beeswax. Crucially, the two recipes appeared in separate layers, meaning they were applied at different times during the ship’s working life. The vessel was not coated once and forgotten. It was treated, put back to sea, and treated again, sometimes with a different formula.
Why add beeswax? The study does not quantify a specific performance advantage, and the authors do not state a definitive reason. The following possibilities are inferences drawn from the material properties, not conclusions reported in the paper: beeswax may have improved flexibility, helping the coating survive the constant swelling and shrinking of waterlogged planks; it may have changed the mixture’s viscosity, making it easier to spread in cooler weather or over rough, previously tarred surfaces; or it may simply have been more available at certain ports or during certain seasons, turning the recipe into a reflection of supply chains as much as engineering preference.
A practice common enough to have its own name
The Ilovik-Paržine 1 findings do not exist in isolation. Research on Adriatic shipwrecks near Pula has identified juniper and pine as the primary botanical sources of pitch on local vessels, pointing to the systematic harvesting of resinous conifers for maritime use along the Croatian coast. That body of comparative work also highlights a term from antiquity: the Roman naturalist Pliny the Elder, in Book XVI of his Natural History, used the word “zopissa” to describe pitch-and-wax mixtures scraped from ship hulls. The word itself is telling: a blend common enough to earn its own vocabulary was not an experiment. It was standard practice.
Farther afield, conifer tar was chemically identified on the keel and hull planking of the Ma’agan Mikhael Ship, a fifth-century BC vessel excavated off the coast of Israel. That work, published by Yaacov Kahanov and Patrice Pomey in the late 1990s and early 2000s as part of the vessel’s post-excavation analysis, used GC/MS to pick out resin-derived compounds after millennia of submersion, helping establish that tar-and-beeswax coatings remain chemically identifiable even in degraded underwater contexts. Separate analyses of organic residues from Mediterranean amphorae have reinforced the same point, showing that conifer-derived products can be reliably traced in archaeological material long after deposition. The Ilovik-Paržine 1 team built on all of this groundwork.
What the study does not yet answer
Several gaps remain. The published paper does not map exactly where on the hull each of the 10 samples was collected. Without that spatial detail, it is hard to tell whether the crew reserved the beeswax-enriched formula for high-stress zones, such as the waterline, plank seams, or areas around impact damage, or whether they applied it more broadly during certain repair episodes.
The timing between coating applications is also unknown. Multiple layers clearly exist, but whether the ship was re-tarred annually, after major voyages, or only in response to visible deterioration cannot be determined from chemistry alone. No dendrochronological data tied to specific coating episodes, and no surviving maintenance logs for comparable vessels, exist to fill that gap.
Quantitative comparisons across sites are limited, too. The Pula wrecks, the Ma’agan Mikhael Ship, and Ilovik-Paržine 1 all show conifer-derived coatings, but exact resin-to-wax ratios have not been compiled into a single comparative dataset. That makes it difficult to judge whether the Ilovik-Paržine 1 recipes were typical of Adriatic shipbuilding or a regional variation shaped by local timber, climate, or trade networks.
What a patched hull says about ancient economics
For all the open questions, the multiple repair layers carry a clear economic signal. A ship that was patched repeatedly was a ship worth patching. Pine tar had to be produced by slowly heating resinous wood in kilns, a labor-intensive process. Beeswax was a traded commodity with competing uses in lighting, medicine, metalworking, and craft production. Choosing to spread both materials across a hull was not casual. It was a calculated trade-off: the cost of waterproofing weighed against the revenue generated by keeping the vessel at sea and its cargo moving.
The coatings on Ilovik-Paržine 1 function, in that sense, as a maintenance ledger preserved in organic chemistry. They show that Roman Republican maritime operators managed hull decay with targeted interventions and adaptable formulas rather than accepting it as inevitable. As more wrecks across the Mediterranean are sampled with comparable analytical methods, and as those datasets become interoperable, archaeologists may be able to move beyond isolated case studies toward regional models of ship upkeep, resource provisioning, and the practical knowledge that kept ancient trade networks running.
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*This article was researched with the help of AI, with human editors creating the final content.
