Pollen grains trapped for centuries inside the waterproofing pitch of an ancient Roman ship have allowed scientists to reconstruct the vessel’s movements and repair history across the Adriatic Sea. The discovery creates the first detailed itinerary of a Roman merchant ship drawn not from cargo or coins, but from the sticky materials that kept its hull seaworthy.
The vessel, called Ilovik-Paržine 1, sank roughly 2,200 years ago off the coast of Ilovik Island, Croatia. In a study published in the journalFrontiers in Materials on April 24, 2026, researchers from France and Croatia showed that the ship’s adhesive coatings preserved a layered record of where the vessel was built, where it stopped for repairs, and how maritime knowledge moved across the Mediterranean.
The team combined chemical analysis with palynology to examine ten samples of waterproofing taken from different spots on the wreck. What surfaced was evidence of at least four distinct coating applications, each tied to a different phase in the ship’s working life.
An Itinerary Written in Tar and Beeswax
The wreck of Ilovik-Paržine 1 was first discovered in 2016 in Paržine Bay. Over five annual excavation campaigns, the Croatian Conservation Institute and France’s Centre Camille Jullian uncovered a merchant vessel dating to roughly 170 B.C., a period when Rome’s influence was expanding fast across the Mediterranean. Earlier analysis of the ship’s ballast stones pointed to a beach near Brundisium, what is now Brindisi in southern Italy, as its likely construction site.
Brindisi was one of the Adriatic’s most important ports during the Roman Republic. The coating analysis reinforces that origin story. Pollen trapped in the earliest layers of pitch matched vegetation patterns characteristic of Apulia, a region known for Mediterranean shrublands dotted with olive, hazel, and holly oak.
The coatings also told a longer story. As the ship sailed and needed upkeep, crews brushed on fresh layers of waterproofing. Each application snagged local pollen from the surrounding environment, effectively timestamping where the repair happened.
The Sticky Science Behind a 2,200-Year-Old Secret
Most of the samples consisted of pitch, a black tar produced by heating conifer wood, probably pine, under oxygen-starved conditions. The molecular analysis, performed using gas chromatography-mass spectrometry, identified a dominance of diterpene biomarkers characteristic of the Pinaceae family. High levels of dehydroabietic acid and the presence of aromatic hydrocarbons such as retene signaled the resin had been heated past 300 degrees Celsius.
One sample stood out. Designated PA 101, it held a mixture of pitch and beeswax. The ancient Roman author Pliny the Elder named this blend zopissa in his encyclopedic work Natural History. Adding wax makes the coating more flexible when cold and lowers its viscosity when hot, which simplifies application during repairs at sea or in a hurry. Long-chain wax esters in the sample confirmed the beeswax component.
“Chemically, on this wreck, the surprise was the discovery of a sample composed of pitch and beeswax, in contrast to the majority of samples which consisted solely of pitch,” said corresponding author Armelle Charrié of the University of Strasbourg, in the study published by Frontiers.
The zopissa find links Ilovik-Paržine 1 to a broader Mediterranean shipbuilding tradition. Archaeologists have identified the same mixture on earlier vessels, including a Greek-era wreck off Marseille from the seventh century B.C. “This example thus illustrates the circulation of technical knowledge and the phenomena of technological transfer across the Mediterranean basin,” Charrié told Discover Magazine.
Tiny Pollen, Massive Detective Work
Pollen analysis provided the decisive tool for telling repair episodes apart. Many of the pitch layers looked nearly identical under chemical scrutiny, but the pollen grains trapped inside them revealed distinct environmental signatures.
Palynologist David Kaniewski at the TRACES laboratory in Toulouse led this part of the work. The team identified four separate pollen-derived vegetation patterns across the ten samples. Mediterranean forest dominated by holly oak and rockrose appeared in one sample. A second showed juniper and heather scrubland. A third sample carried traces of wet meadows rich with sedges, grasses, and cabbage-family plants. The rest clustered around a matorral landscape of cultivated olive, hazel, aster flowers, and coastal alder forest.
The way these patterns were distributed on the hull hinted at a repair logic. The ship’s stern and central sections shared a consistent coating signature. The bow area preserved three different batches. This suggests the vessel underwent multiple targeted repairs over its lifetime rather than a single complete recoating. Different hull sections probably deteriorated at different rates, or crews simply applied fresh material where leaks demanded it.
What Sunken Glue Can Teach Modern Archaeology
Ancient ship maintenance has long been one of the least visible corners of maritime archaeology. Scholars routinely study timber origins, but the non-wood materials that actually kept vessels afloat have drawn far less attention. “We don’t know any archaeological evidence or sources that address the subject of ancient Roman ship maintenance,” Charrié said. “The question is how to identify these repairs if no written records exist.”
The Ilovik-Paržine 1 study supplies an answer. By linking molecular and palynological techniques, the research team demonstrated that adhesive coatings can act as environmental archives. The authors wrote that this “analytical strategy opens new fields of investigation in naval archaeology.”
The approach is already moving to other wrecks in the Adriatic. Researchers with the Adriboats program continue to examine coatings from sewn boats and mortise-and-tenon vessels scattered along the Dalmatian coast. Each sample carries the potential to reveal not just what ancient ships were made of, but where they went and how their crews kept them sailing.
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