Adriatic shipwreck shows signs of waterproofing and repair with novel materials

(CN) — Repairs for necessary items in life are often a pain, entailing extra time, attention and detail to ensure a lasting fix. That may be even more true if the repairs involve seafaring vessels from approximately 2,200 years ago.

Or that is what scientists have come to find when analyzing the components of ancient waterproofing on Roman shipwrecks. In a study published in Frontiers in Materials Thursday, researchers with the Laboratory of Mass Spectrometry of Interactions and Systems at the Université de Strasbourg in France examined the materials used to keep out seawater, microorganisms and wood-eating nuisances such as shipworms from destroying wood-hulled vessels.

The researchers specifically looked at the protective coating of a Roman Republic ship called Ilovik–Paržine 1 that was wrecked 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," Armelle Charrié, an archaeometrist — or a scientist who applies the scientific method to archaeology — and the first author of the study, said in a statement.

Charrié and a team of archaeologists found two different kinds of material on the ship: one made of pine tar, also called pitch, and another that was a mixture of pine tar and beeswax.

By analyzing the pollen in beeswax coating, the researchers were able to identify the plant the pollen was from and the region the plant grew in — ostensibly indicating where the sailors made their repairs.

The identified materials came from landscapes as diverse as forests of holly oak and pine inland from the Mediterranean and Adriatic coasts to matorral, a kind of shrubland featuring olive and hazel trees, to instances of alder and ash, fir and beech, which suggests environments close to rivers or mountains, such as the Istria and Dalmatia ranges in Croatia.

The study highlights common patterns within the same maritime basin while also revealing regional specificities, Charrié said in an email to Courthouse News.

"It also allows us to trace the evolution of practices over time, in relation to technological advancements," she said about the study. "Furthermore, the analysis of materials underscores the variability of techniques across maritime basins, notably in connection with resource availability."

However, as far as hypothesizing how the wax was obtained — was there an industry of beekeepers collecting wax for ship repairs or were sailors hoofing it far inland to collect wax from wild hives — the scientists pose no theories.

"We have no answers to these questions," said Charrié. "For this shipwreck, we don't know any archaeological evidence or sources that address this subject."

Questions persist about what the proportions of the mixture were — how much of pitch and wax was needed to get it just right?

Charrié noted the wax was added to modify the physical and chemical characteristics of the pitch, and the resulting adhesive mixture was "more malleable and less brittle in the long term, while retaining its hydrophobic properties."

She said the use of wax at the time wasn't limited to naval need — it was used as a mortar for a Roman wall revetment, or protective sloped infrastructure employed around shorelines and embankments to stop erosion.

But how much wax was utilized requires further study.

"Perhaps not much is needed?" posits Charrié. "The question remains open."