A Brittle Coating on a 2,200-Year-Old Roman Shipwreck Reveals How Ancient Sailors Kept Their Ships Afloat

More than two millennia ago, a Roman Republic ship carrying timber and wine sank in the Adriatic Sea, off the coast of what is now Croatia. Remarkably, the wreck offers clear evidence of an elaborate effort to waterproof its wooden hull, shielding the vessel from the corrosive effects of seawater. Discovered in 2016 and named Ilovik–Paržine 1, the ship offers a detailed glimpse into ancient shipbuilding techniques.

According to a study published this spring in Frontiers in Materials, the hull was coated with conifer-derived pitch, and one sample contained a mixture of pitch and beeswax. The findings highlight an often overlooked aspect of ancient seafaring: the organic materials used to keep wooden vessels watertight. As Charrié-Duhaut told Chemistry World’s Mason Wakley in April, “There’s a long history of coating” in shipbuilding.

Because shipbuilders would have had access to different raw materials depending on where they lived, the coatings differ as well, she said, “Each boat has its own history.” Charrié-Duhaut and her coauthors analyzed ten samples of the Ilovik–Paržine 1’s coating. They found molecular fingerprints characteristic of heat-treated conifer material, particularly from the Pinaceae family, indicating that the coating was made from conifer-derived tar or pitch. One sample, however, contained a mixture of tar and beeswax, a formulation associated with ancient Greek shipbuilding and referred to in ancient sources as zopissa.

Adding beeswax to tar would have made the coating more flexible and easier to apply. As Pliny the Elder wrote in Natural History, “Zopissa is the pitch, macerated with salt-water and wax, that has been scraped from off the bottoms of ships.” The use of zopissa is an “archaic Greek tradition,” Charrié and study coauthor Quentin Couillebault, a bioarchaeologist at Aix-Marseille University, tell Gizmodo’s Gayoung Lee. Its presence on a Roman ship built centuries later, they explain, is consistent with the “circulation of technical knowledge” and “technological transfer across the Mediterranean basin.” But the coating revealed more than its composition.

Sticky pitch can trap airborne pollen—tiny grains released by plants during reproduction. By analyzing the types and relative abundance of pollen lodged in the material, the researchers gained clues about where it might have been produced or applied. The pollen preserved in the pitches points to environments where holm oak, pine, olive, alder, ash and hazel grew.

These plants are characteristic of Mediterranean and Adriatic coasts and valleys and are consistent with the ship’s proposed construction area near Brindisi, on Italy’s southeastern coast. Previous analysis of the ship’s ballast found a strong geological match with the Brindisi region, and suggested that the ballast was loaded there when the ship was built. Statistical analysis identified four to five distinct coating batches, which may reflect successive repairs or separate applications during construction or refitting.