Since people began to sail, boats needed protection against water, salt, microorganisms, and marine animals like worms. However, until the mid-20th century, researchers paid little attention to non-woody materials used in ancient shipbuilding. Waterproofing products, in particular, remain under-studied.
A new paper published in Frontiers in Materials helps to fill that gap. Researchers from France and Croatia analyzed the protective coating of the Roman shipwreck of the Ilovik-Paržine 1, which sank about 2,200 years ago off the coast of what is now Croatia.
“In archaeology, little attention is paid to organic waterproofing materials. However, they are essential for navigation on seas or rivers and are true witnesses to past naval technologies,” explained the lead author, Dr. Armelle Charrié, archaeometrist at the Mass Spectrometry Laboratory of Interactions and Systems in Strasbourg.
“In studying the coatings, we found two distinct types on this vessel: one made of pine tar, also called pitch, and the other a mixture of pine tar and beeswax. The analysis of pollen in the coating allowed us to identify the plant taxa present in the immediate environment during the construction or repairs of the ship.”
Pine tar and beeswax protected the hull
The wreck was discovered in 2016, and both the vessel and its cargo have been investigated several times since then. This study is the first to combine molecular and pollen analysis to identify the ship's coatings and reconstruct the vegetation present when those materials were produced and applied to the hull.
The research was conducted in collaboration between the Underwater Archaeology Department of the Croatian Conservation Institute and the ADRIBOATS program of the Camille Jullian Center at Aix-Marseille University in France.
“Some regions of the Adriatic have particular characteristics that led local populations to develop a specific style of shipbuilding,” noted Charrié. “Only studies like ours provide an overview of these traditions that testify to genuine know-how and diverse traditions.”
To investigate the coatings, the researchers conducted structural, molecular, and pollen analyses. They used methods such as mass spectrometry, which allows for the identification and measurement of unknown substances within complex organic mixtures. The team analyzed 10 coating samples to determine the biological origin of the natural materials used in the vessel.
Ancient pollen preserved in sticky pitch
The molecular analysis revealed compounds associated with pines, showing that all samples were dominated by heated conifer resin or conifer tar, also known as pitch. One sample, however, contained a distinct formulation made of beeswax and tar. This mixture—known to Greek shipbuilders as zopissa—enhances the flexibility of the adhesive and is easier to apply hot.
Since pitch is naturally sticky, it can capture pollen from nearby vegetation and preserve it for long periods. By studying the types of pollen trapped in the coatings and measuring their relative abundance, the researchers were able to narrow down where some of the pitch may have been produced or reapplied during repairs.
The pollen recovered from the Ilovik-Paržine 1 pointed to a wide range of environments. Some came from typical landscapes of Mediterranean and Adriatic coasts and valleys, including oak and pine forests, as well as Mediterranean scrub where olives and hazelnuts grow. Pollen from alder and ash indicated vegetation associated with riverbanks and shorelines, present along the coast and in the nearby interior. Small amounts of spruce and beech also appeared, trees linked to mountainous terrains characteristic of the northeastern Adriatic coast, where the Istrian and Dalmatian ranges are relatively close to the sea.
The analysis also suggests that the vessel received between four and five distinct batches of coating over time. The stern and the central section appear to have been covered with the same material, while three different batches of coating were identified at the bow. This pattern may indicate that the ship was repaired repeatedly, with materials obtained from different locations around the Mediterranean.
Evidence of repeated repairs across the Adriatic
Previous investigations into the vessel's ballast pointed to Brundisium—now Brindisi—on the southeastern coast of Italy as the place where the ship was built. The new pollen evidence suggests that some of its coatings may also have been applied in that area. Other layers, however, may have been added along the northeastern Adriatic coast, near where the wreck was ultimately found.
“While it seems obvious that ships sailing long distances need repairs, it is simply not easy to prove,” concluded Charrié. “Pollen has been very useful in identifying different coatings where the molecular profiles were identical.”
