Oysters and pitch on plank. © Sydney Metro.

Cleaning the Barangaroo Boat

How does one clean a boat?

I was once turfed off the side of a working boat in scuba gear, handed a brush and told to not come up till it was clean. In this scenario, there were no issues with becoming filthy myself, as I was underwater – but how does one clean a 200 year old, heavily sedimented, in pieces, on land, archaeological boat? With dish brushes, toothbrushes, plastic scrapers, and care. Read on, and find out more!

All wrapped up

The Barangaroo Boat was excavated at none other than Barangaroo, and was discovered as a result of archaeological survey done before the construction of a Sydney Metro asset. The excavating archaeologists were Casey & Lowe and Cosmos Archaeology. To find out more visit the Sydney Metro website or our blog under the ‘Barangaroo Boat’ tag.

The timbers were subsequently stored in refrigerated containers, and then were once again rediscovered by the Silentworld Foundation team, in conjunction with Australian National Maritime Museum (ANMM).

At this point, our task was to document the timbers with 3D scanning – but in order to accurately document, the timbers had to be free of mud. Thus began the undoubtedly messiest portion of this project! Each timber had been painstakingly wrapped with wetted geotextile, and then encased in thick plastic to prevent it drying out. The timbers were then carefully supported and boxed so that they would emerge from their hibernation still in the shapes they had been shaped into 200 years ago, and settled into in the ground.

The timbers of all shapes and sizes were covered in a variety of different sediments. Some of the first timbers we took out were curved frames and futtocks, and they collected a fine sediment, undoubtedly from their intertidal location, in the joggles and niches cut into them. Washing away this sediment with a hose and plastic dish brush led to a harder substrate underneath – wood? Ian Panter, head conservator from York Archaeological Trust, guessed no – pitch perhaps. Hearty sniffs confirmed this was the case – it smelt like a road on a hot day.

Head conservator Ian Panter cleaning © Sydney Metro

Layers of pitch

'White stuff' being cleaned from a plank. © Sydney Metro.

Much of the pitch across many of the planks, it was discovered as we went, was too hardened to remove without damaging the wood surface underneath. However, one particular plank yielded softened pitch, which was pliable and easily removed with a plastic scraper without causing any damage to the surface of the plank – it would be interesting to analyse this particular batch of pitch and compare it to the hardened, brittle pitch, to see if there may be a difference in recipe, or perhaps even degradation.

Aside from the sediment and the pitch that coated the timbers – once we got to cleaning the planks as opposed to the frames, we started to see a lot of what was, according to ANMM’s Kieran Hosty, ‘white stuff’. This is believed to have been used as an antifoul, and was potentially made up of whale oil, rosin, and brimstone. Interestingly, the samples found on our timbers also appeared to have crushed shells included in the mix. As with the pitch, there were varying levels of pliability; most of the white stuff was buttery, and very easily removed. Some of it was slightly crisper, and came off in chunks, but still was easily removed with a plastic scraper and saved for testing. In a couple of planks, however, the white stuff was cemented on to the wood – no amount of water streams, scrubbing with toothbrushes, dish brushes, or scraping with plastic scrapers would remove it.

A pitch covered plank. © Sydney Metro

Removing the oysters

We have previously posted a video of the process of oyster removal – this was one of the most satisfying tasks. Once we got to the timbers that made up the external hull, we started to find a lot of oysters still clinging to the surface of the wood – although I shouldn’t say the surface of the wood. The oysters often seemed to prefer pitch as a substrate – whether this was because there was no bare wood available for them to latch onto when they began to grow, or whether they preferred the pitch – who knows, and they’re no longer talking!

They were removed, some easily, some with a lot more effort, by carefully levering underneath the oyster with a plastic scraper. If this was unsuccessful, I found that scrubbing around the shell with a toothbrush would help loosen the bond. All oyster shells were kept for analysis, as we hope they will be able to tell us something about the environment in which the boat spent the majority of its time.

Oysters and pitch on plank. © Sydney Metro.

Although dirty, and very smelly work – even 200 year old oysters smell, though perhaps this shouldn’t be a surprise – it was a true joy being able to handle each and every one of the planks, to become familiar with the boat, and to uncover secrets as we carefully cleaned the planks. That truly isn’t just a way of signing off – we really uncovered some fascinating secrets.

Conservator Heather Berry after a day of cleaning.

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