Scientists analyzing organic hull coatings on a 2,200-year-old Roman shipwreck discovered off Croatia have uncovered detailed evidence of ancient ship waterproofing and maintenance.
The merchant vessel, known as Ilovik-Paržine 1, sank in the Adriatic Sea during the middle of the second century BC while transporting timber and wine. Research published in 2026 in the journal Frontiers in Materials reveals how ancient shipbuilders applied conifer pitch, beeswax, and plant resins to protect the wooden hull from saltwater damage.
During the Roman Republic, maritime trade flourished across the Mediterranean and Adriatic seas, requiring merchant vessels to endure lengthy voyages. Protecting wooden hulls from decay and marine organisms was essential for sea trading routes connecting the Italian peninsula with the Balkan coast.
Chemical examination of ten coating samples taken from the 21-meter hull identified molecular signatures of heated coniferous trees, specifically from the Pinaceae family. The tar and pitch served as a primary barrier against seawater deterioration.
One specific sample revealed a specialized mixture combining pine pitch with beeswax. This preparation corresponds to zopissa, an ancient waterproofing formula documented in Greek naval traditions to make hull coatings more flexible and easier to apply.
The Roman naturalist Pliny the Elder later described zopissa in his work Natural History as a mixture of pitch, wax, and saltwater scraped from ship bottoms. Researchers noted that finding this formula on a later Roman vessel demonstrates how technical maritime knowledge spread across the ancient Mediterranean.
Pollen trapped in hull pitch
The sticky pitch on the hull also acted as a natural time capsule, capturing ancient pollen grains during its application. Laboratory tests identified pollen from evergreen oaks, pines, olives, alders, ashes, and hazel trees, reflecting vegetation typical of Mediterranean coastal areas and river valleys.
These botanical traces support earlier geological findings from the ship's ballast stones, which strongly linked the vessel's origin to the area around Brindisi in southeastern Italy. Brindisi served as a vital port city connecting Rome to eastern trade routes.
The scientific team distinguished between four and five separate coating batches across the hull. Certain samples contained trace amounts of fir and beech pollen, species common to the mountainous regions of the northeastern Adriatic near Istria and Dalmatia.
Evidence of maritime maintenance
Variations in pollen composition indicate that the 21-meter vessel received initial protective layers during construction and subsequent re-coatings during later repair work. Armelle Charrié-Duhaut, the lead author of the study, explained that while it seemed obvious that ships sailing long distances required repairs, physical evidence proving it was rare.
Microscopic pollen analysis allowed researchers to differentiate between coating layers that otherwise shared identical chemical profiles. The evidence shows that Ilovik-Paržine 1 operated between the western and eastern shores of the Adriatic Sea, receiving protective treatments at different stages of its life before sinking more than two millennia ago.
