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The Barangaroo Boat
The Barangaroo Boat was found in the exact location as the proposed new Metro station and had to be removed before further work could be done. All images Kieran Hosty/ Australian National Maritime Museum for Sydney Metro. Used with permission
Archaeology and conservation of an early colonial vessel
In September 2018, archaeologists from the Silentworld Foundation and the Australian National Maritime Museum were invited to participate in the excavation and recovery of an early 19th-century timber boat from the former shoreline of Cockle Bay at Barangaroo, Sydney. Silentworld Foundation and the York Archaeological Trust, assisted by the Australian National Maritime Museum and Ubi3D, are leading the conservation effort to preserve the boat for future generations. Irini Malliaros, Heather Berry, Kieran Hosty, Dr James Hunter and Ian Panter share the story of this project, financed by Sydney Metro and the NSW Government.
THE NEW SOUTH WALES GOVERNMENT’S long-term strategic rail plan for Sydney incorporates the development of a European-style metro system operating independently of the existing rail network. Sydney Metro was formed in 2015 with four proposed lines. During construction of the Barangaroo Metro Station (part of the City and Southwest Line), archaeologists from Casey & Lowe – working under contract to John Holland CPB Ghella (JHCPBG) – discovered the archaeological remains of an early 19th-century wooden clinker-built vessel within the approved the Metro station’s ‘station box’. Cosmos Coroneos from Cosmos Archaeology, a specialist maritime archaeological consultant, was contracted to advise and manage the site during in situ recording, excavation and subsequent removal of the boat. Initial in situ analysis of the Barangaroo Boat carried out by Casey & Lowe and Cosmos Archaeology indicated that its 12-metre-long, 3-metre-wide surviving hull comprises overlapping, or ‘clinker’, planking with floors and futtocks added secondarily for reinforcement. The hull was coated in pitch, double-planked, and ironfastened. The bottom (bilge) of the boat’s port side is preserved up to the end of the floor timbers. At midships, the starboard hull appears to be intact to the gunwale while the bow is badly degraded.1 Timber sampling revealed the boat’s hull planks were milled from hardwoods such as Sydney blue gum (Eucalyptus saligna), while some of the roughly hewn futtocks (upper frames, or ‘ribs’) were identified as Banksia species.2 The vessel’s floors (lower ribs that crossed the keel) are generally either stringybark (Eucalyptus species) or spotted gum (Corymbia maculata). It is very likely that the vessel was locally built – an assertion supported by the species identification of the timber samples. The boat was covered by marine sediments, as well as erosional runoff that had washed into the site. It was also located beneath a stone wall constructed between 1855 and the 1860s, which suggests a much older vintage for the boat, perhaps as early as the 1820s or 1830s.3 At a national level, only four Australian-built vessels that predate 1850 have been found and archaeologically documented. The Barangaroo Boat is unique because it is the earliest colonial-built vessel in Australia that has been archaeologically recorded, fully excavated, and recovered in its entirety.4
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Recovery and Packing Given the Barangaroo Boat’s archaeological and historical significance, several possible recovery and management options were developed by Casey & Lowe in conjunction with Cosmos Archaeology, International Conservation Services, Sydney Metro and Heritage NSW. They were assisted by interstate and international conservation experts including Vicki Richards from the Western Australian Museum, Dr James Delgardo from SEARCH, Fred Hocker from the Vasa Museum and Ian Panter from the York Archaeological Trust.5 Recovery options included excavation, documentation and destruction, or a ‘whole structure block lift’, in which the boat would be kept intact, recovered in a block complete with its surrounding soil and sediment, and then excavated off-site in a controlled environment. Alternatively, a controlled, fragmented or disassembled lift could be employed, in which the boat would be carefully recorded, then excavated in situ before being completely disassembled and moved to a controlled environment for conservation and reconstruction.6
The first option was dismissed due to the significance of the vessel. The second approach was investigated initially but then abandoned, based on engineering difficulties and the higher potential to damage the item. The boat’s surviving hull lay directly over Sydney sandstone substrate, and tunnelling underneath was not possible without putting it at considerable risk. The small size of the boat and the corrosion of the fastenings also meant that there was little holding the timber together. Consequently, based on advice from the international conservation experts, the decision was made in early October 2018 to completely excavate, disassemble and recover the boat’s surviving components. Assisting the team recovering and recording the boat were archaeologists Irini Malliaros and Paul Hundley (Silentworld Foundation), and Dr James Hunter and Kieran Hosty (Australian National Maritime Museum). Once exposed, the various layers of hull structure were assigned context numbers and each timber carefully tagged with a unique identifying number, which was placed at its forward end. All timbers were then accurately documented in situ with 3D recording techniques such as photogrammetry, as well as standard digital photography and videography. A variety of implements and tools, including plastic plates, trowels, icing spatulas and cake slicers, were used to separate each hull element from its neighbour before it was carefully removed. This process could take several hours or a whole day, depending on the condition of the timbers. In the case of the boat’s ceiling (inner) planks, the surviving wood had the consistency and structural integrity of soggy Weet-Bix. Under the supervision of Cos Coroneos from Cosmos Archaeology and Karina Acton from International Conservation Services, during the recovery each timber was placed in a supporting cradle and transported to an artefact processing area, where it was photographed and archaeologically recorded in greater detail. Its physical condition and state of preservation was noted, after which the item was wrapped in geofabric soaked with fresh water. To prevent the timbers from drying out and becoming damaged while in storage prior to conservation, all were sealed within black plastic sheeting secured with cable ties.
02 01 Dr James Hunter excavating the lower bilge area of the starboard side of the Barangaroo Boat. Because of the fragile nature of the timbers, the archaeologists worked from planks placed over the hull.
02 Irini Malliaros from the Silentworld Foundation and two conservators from International Conservation Services splinting a ceiling plank prior to lifting. The planks were so soft they required additional support to recover them.
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02 01 Irini Malliaros, Heather Berry and Paul Hundley from the Silentworld Foundation placing timbers into conservation tanks. The timbers are held by racks which have been modified to preserve the shape of the timbers during the lengthy conservation treatment.
02 While the work was being carried out, the fragile timbers had to be kept wet to prevent further degradation.
Structural elements that exhibited a pronounced curve or shape were mounted on a flat wooden support or secured within boxes fitted with shaped metal brackets to preserve each timber’s shape as it was worse right after separation from the rest of the hull. This step proved critical, as it preserved the original shape of each timber – a detail necessary to ensure the boat’s successful reassembly and reconstruction. Once securely packed and numbered, the timbers were placed in two 13-metre-long refrigerated shipping containers. They were cooled to an internal temperature of 4° Celsius to minimise water loss, biological activity and structural degradation. This container remained their home until the conservation process commenced.
Conservation and 3D Recording Sydney Metro, the Barangaroo Boat’s owner, now faced a significant dilemma. Conservation of a large, waterlogged wooden vessel of such immense historical and archaeological significance had not been undertaken in Australia since recovery and conservation of the stern port quarter of the 1629 Batavia shipwreck in the mid-1970s. While in storage, the boat’s timbers were carefully monitored by Dr Ian MacLeod (Heritage Conservation Solutions) and Dave McBeath (OHM Consultants). At the same time, Sydney Metro engaged the York Archaeological Trust and Silentworld Foundation to develop and implement a conservation and facilities plan. Their expertise and involvement allowed for implementation of best-practice techniques developed in England and Wales during recent archaeological conservation projects such as the Newport Medieval Ship, the Swash Channel Wreck and HMS Invincible. Ian Panter was later contracted to be the supervising conservator for the Barangaroo Boat’s conservation, while Silentworld Foundation assumed overall project management. Sydney Metro established a waterlogged wood conservation facility and heritage store to accommodate this work.
The Barangaroo Boat conservation and reconstruction approach includes initial cleaning, detailed recording, chemical treatment, freeze-drying, and eventual reconstruction and interpretation. Significantly, it also allowed for conservators and archaeologists from New South Wales to be invited to participate in the project at each stage in order to build future capacity in the treatment of waterlogged archaeological wood. Inspection and cleaning of hull timbers was relatively straightforward and carried out immediately upon their removal from the refrigerated containers. Each timber was unpacked, photographed and inspected for damage (including mould and/or sulphur deposits). A core group of archaeologists and conservators, assisted by volunteers, cleaned the timbers with fresh water, plastic scrapers, toothbrushes, dental picks and wooden skewers. Each timber was completely cleaned of sediment to inhibit microbial activity, as well as to reveal fine surface details and allow for effective penetration of conservation treatment chemicals. The individual timbers were then recorded with a state-of-the-art Artec Structured Light Scanner. The scanner produced thousands of electronic images that were combined digitally to generate incredibly accurate and detailed 3D models. This approach, known as the Annotated Scans Method (ASM), was initially developed in 2017 by 3D recording company Ubi3D in cooperation with the Cultural Heritage Agency of Mecklenburg-Vorpommern, Germany. Ubi3D’s Thomas Van Damme was contracted by Sydney Metro to scan the Barangaroo Boat and instruct project archaeologists in ASM. This method is time and cost efficient, generating far more detailed images and information than traditional recording methods such as full-scale 2D tracing by hand. It is also superior to the combination of FaroArm laser scanner and Rhinoceros Computer-Assisted Drawing software, which was the existing professional standard in digital shipwreck timber recording. Structured light scanning results in high-resolution 3D colour models that are digitally annotated with Rhinoceros software. The annotated scans reveal patterns and details in the timbers and produce a data set that is invaluable to the interpretation and eventual reconstruction of the vessel. Unannotated scans can also be used to produce exact 3D printed replicas of individual timbers, or even the entire boat.
Digital 3D replicas can be compared with the boat’s actual timbers after conservation, and during subsequent reconstruction and display to test their shrinkage and dimensional stability. Models can also be utilised prior to completion of the conservation process, to assist development of computer-based and physical models to determine the Barangaroo Boat’s original hull form. The same models will also facilitate reassembly of the original timbers when the boat is ultimately reconstructed and displayed.
01 Paul Hundley from the Silentworld Foundation places polyethylene glycol (PEG) into a conservation tank. Depending on the size of the tank, 225–450 kilograms of PEG were added at a time to slowly increase the concentration of PEG up to 40 per cent. 02 Irini Malliaros from the Silentworld Foundation using a structured light scanner to record the Barangaroo Boat. The scanner takes thousands of individual images which are then processed to reproduce a 3D model of the timber. 01
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Following the 3D recording regimen, the boat’s approximately 300 individual timber elements were placed into four water-filled tanks for desalination and additional cleaning. This too was an essential stage as it reduced the concentration within each timber of harmful contaminants such as chlorides from the saline marine environment. These contaminants could detrimentally impact long-term preservation of the timbers, and potentially limit the success of proposed conservation treatments.
Following a soak in fresh tap water, each timber entered the first official stage of active conservation: treatment with the chelating agent ethylenediaminetetraacetic acid (EDTA) disodium salt. EDTA is used to reduce iron in cultural materials and is therefore particularly relevant to the field of maritime archaeological conservation. In the case of the Barangaroo Boat, it was used to mitigate iron staining on timbers that resulted from corrosion of iron fasteners. The removal of iron is an important phase in waterlogged wood conservation as it can negatively interact with the next stage of treatment: consolidation with polyethylene glycol (PEG) wax. The reaction between iron and PEG can contribute to long term degradation of timbers after the conservation process is complete. EDTA was added to the treatment tanks to assist removal of iron staining. Subsequently, each timber was manually cleaned by conservators, archaeologists and volunteers. Upon completion of the EDTA phase, there was no need for further manual handling of the timbers. Each tank was once again filled with fresh water, and a broad-spectrum biocide was added to control microbial activity within the timbers and surrounding water column. The consolidation phase of the conservation process then commenced. Use of PEG wax is a well-researched method that has been applied with a high degree of success over the last 50 years, both in Australia and internationally. The internal cellular structure of waterlogged timber is often heavily degraded, and water present within the wood fills the empty spaces in cells. This allows the timber to retain its original shape. However, if the timber is allowed to dry out, the water within the cells evaporates and resulting surface tension causes them to collapse. This can cause catastrophic damage, including severe shrinking and warping of the original timber surface and structure. PEG wax is added to the treatment tanks in incrementally larger concentrations and mitigates the damage to the timbers by gradually replacing the water in their cellular structure. Under the supervision of Ian Panter and Silentworld Foundation’s conservator Heather Berry, the concentration of PEG wax is slowly being increased in a process that will take several months to complete. The final percentage is dependent upon each timber’s uptake of PEG, as well as its level of preservation. Conservation of the Barangaroo Boat’s hull represents the first instance in which EDTA treatment and PEG wax consolidation have been used on waterlogged Australian native timbers. Consequently, near-constant monitoring is required to ensure the timbers are reacting positively to treatment, in a manner that is expected.
A work in progress Currently, the Barangaroo Boat’s hull timbers are resting in their treatment tanks, supported on wooden frames to ensure maximum chemical penetration during the consolidation phase of the conservation process. Once the final concentration of PEG has been attained, the next conservation phase will commence. All timbers will be vacuum freeze-dried, when residual water in the wood is slowly converted to ice and then vapour under low temperature and pressurized conditions. Once completely dried, the timbers will be cleaned of residual PEG wax before they are reassembled to reconstruct what could be Australia’s earliest known colonial-built vessel.
Ultimately, it is planned that the reconstructed hull will be exhibited alongside associated archaeological artefacts and features, such as sandstone blocks from the 1850s wharf. This tableau will allow us to tell the story of this significant and unique Australian watercraft.
The Barangaroo Boat project is financed by Sydney Metro and the New South Wales Government.
Archaeologists Irini Malliaros and Paul Huntley, and conservator Heather Berry, are with the Silentworld Foundation. Ian Panter is Head of Conservation, the York Archaeological Trust. Kieran Hosty is Manager, Maritime Archaeology, and Dr James Hunter is a maritime archaeologist with the Australian National Maritime Museum.
1 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, Version 4, Casey & Lowe, Cosmos Archaeology, International Conservation Services, 2018, p. 13. 2 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, p. 14. 3 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, pp. 9–13. 4 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, p. 23. 5 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, p. 3. 6 Barangaroo Station, Sydney Metro, Archaeological Relics Management Plan, pp. 39–48.
