Researchers analyzing pollen trapped in the waterproofing layers of long sunken Roman Republic ship find proof that it may have been patched up successively at different locations throughout the Adriatic Sea
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View of the excavation of the bow area of the Ilovik-Paržine 1 shipwreck. In the foreground, the cargo of logs and amphoras can be seen. Archaeologists are working near the structure of the bow complex.
view moreCredit: Adriboats © L. Damelet, CNRS/CCJ
Ever since humans have embarked on sea voyages, they needed to ensure vessels were waterproof, resistant to salty seawater, and could withstand microorganisms or sea-dwellers like worms. Until the mid-20th century, however, the study of non-wood materials used to build ships was overlooked. Even today little work has been done on materials used for waterproofing.
Now, in a new Frontiers in Materials study, researchers in France and Croatia have examined the protective coating of the Roman Republic shipwreck Ilovik–Paržine 1 that sank around 2,200 years ago off the coast of what is now Croatia.
“In archaeology little attention is paid to organic waterproofing materials. Yet they are essential for navigation at sea or on rivers and are true witnesses of past naval technologies,” said first author Dr Armelle Charrié, an archaeometrist at the Laboratory of Mass Spectrometry of Interactions and Systems in Strasbourg. “Studying the coatings, we found two different kinds on this vessel: one made of pine tar, also called pitch, and the other of a mixture of pine tar and beeswax. Analysis of pollen in the coating made it possible to identify the plant taxa present in the immediate environment during the construction or repairs of the ship.”
Resin and wax
The wreck was discovered in 2016 and since then the ship itself and its cargo has been examined multiple times. The current study, however, is the first to combine pollen and molecular analyses to characterize the ship’s coating and vegetation present during its production and application on the hull. The work is a collaboration between the Department for Underwater Archaeology of the Croatian Conservation Institute and the ‘ADRIBOATS’ program of the Centre Camille Jullian at Aix-Marseille University in France.
“Some regions throughout the Adriatic have particular characteristics that led local populations to develop a specific shipbuilding style,” said Charrié. “Only studies like ours offer an overview into these traditions which bear witness to genuine know-how and diverse traditions.”
To examine the coatings, researchers carried out structural, molecular, and pollen analyses using techniques that identify and quantify unknown components in an organic mixture such as mass spectrometry.
Using 10 coating samples, the team identified the biological origin of natural substances used for the ship’s coating by molecular analysis. This ‘molecular fingerprint’ analysis showed molecules characteristic of pine trees, indicating that the main component of all coating samples was heated coniferous resin or coniferous tar, also called pitch. One sample, however, showed that at least some of the coating was made from a different composition of materials, namely beeswax and tar. This mixture – known to Greek shipbuilders as zopissa – improves the adhesive’s flexibility and is easier to apply when hot.
Trapped in pitch
Pitch is adhesive by nature and can trap and preserve pollen from the surrounding landscapes. Analyzing these traces and their respective abundances allowed the researchers to narrow down possible regions where the pitch could have been produced and re-applied during refurbishments.
Pollen from coating samples from the Ilovik–Paržine 1 reflected a high diversity of environments. The identified landscapes included those characteristic of the Mediterranean and Adriatic coasts and valleys, with forests of holly oak and pine as well as matorral – a kind of Mediterranean shrubland – where olive and hazel trees grow. The presence of alder and ash points to vegetation growing close to river- and seashores, which can be found near the coast or in the nearby hinterland. Fir and beech were present in small proportions, too. This vegetation is found in mountainous regions and typical of the north-eastern coastal regions of the Adriatic Sea where the mountain ranges of Istria and Dalmatia are not far.
The team’s findings also indicated that the ship likely underwent four to five distinct batches of coatings. The ship’s stern and central part was covered by the same coating, whereas three batches at the bow were distinct from one another. This, too, could indicate that the ship was patched up successively using materials sourced from various locations throughout the Mediterranean.
Previous research using the ship’s ballast identified Brundisium – today Brindisi – on the south-eastern coast of Italy as the ship’s place of construction. Pollen analysis also suggests that some of the coatings were applied close to there. Other coating layers, however, could have been applied on the north-eastern Adriatic coast, where the shipwreck was discovered.
“While it seems obvious that ships sailing long distances need repairs, it’s simply not easy to demonstrate this,” concluded Charrié. “Pollen has been very useful in identifying different coatings where the molecular profiles were identical.”
Journal
Frontiers in Materials
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