CONSERVATION

The Sirius wreck site is on and around a coral reef with constant wave action from the open sea. It is rated one of the most aggressive for artefact survival. However, the concretion of calcium carbonate (that builds up on metal objects over the years) actually provided a protective layer and preserved the surface detail of many objects. Initial conservation was carried out as the objects were recovered from the sea during official expeditions from 1983 to 1988 and in 2002.

The size and isolation of Norfolk Island provided both pros and cons for the conservators. One of the pros was that the conservation area could be set up in the immediate area to the dive site, in convict built boat sheds on the shorefront. One of the cons was the lack of availability of supplies for treatments. Norfolk’s isolation can be an impediment at times as everything must come onto the island via cargo ship or passenger aircraft. However, this obstacle was overcome by the ingenuity and improvisation of the expedition members and assistance and interest from locals.

The conservation treatment carried out during the expeditions involved general first aid and preparatory work for long-term treatments. Some objects were stabilised and transported to the Western Australian Maritime Museum to take advantage of the professional skills and equipment of this institution. The expedition members instructed a number of locals in conservation techniques enabling them to carry on the monitoring and conserving of some 1000 artefacts recovered from this site.

However by 2005 objects required further treatments. Dr Nigel Erskine and Karina Acton of the Australian National Maritime Museum were contracted to undertake a conservation assessment of the collection in October 2005. This report for the Heritage Division of the Department of Environment and Heritage concluded that conservation work was a necessity. John Carpenter and Richard Garcia from the Western Australian Museum visited the island during July and August of 2006 to carry out the work. Their principal aims were to examine all artefacts and carry out treatments as necessary, provide training to Norfolk Island Museum personnel in basic conservation techniques and procedural information for the ongoing maintenance of the collection.

In August 2008 Karina Acton of International Conservation Services Pty Ltd provided an additional conservation assessment of the collection, funded by the Historic Shipwrecks Program. This assessment included recording the condition of the collection and noting any changes since 2006. An ongoing maintenance, monitoring and treatment schedule was developed and Norfolk Island Museum staff received further training in the area. Karina returned to Norfolk in October of 2008 to review the work that had been carried out since August and provided additional conservation training and recommendations for future work.

Today, on-going conservation is carried out by Norfolk Island Museum staff, with on-going specialist advice from Jon Carpenter and Richard Garica from Western Australian Maritime Museum, Karina Acton from International Conservation Services and Dr. Nigel Erskine, Australian National Maritime Museum.

Some Conservation Stories:

Carronade

Material:   (Ferrous) Cast Iron
Sirius Number:   SI 626

Measurements:  
Weight 442 kg
Length:  1.02 metres
Bore:   131 mm


The Sirius carried six 18 pounder carronades. These extremely short-barrelled guns had the nickname of ‘smashers’ and were particularly used for short distance battles, basically clearing the decks! The Carron Iron Company in Falkirk, Scotland manufactured the original design for approximately two years. The British Navy were then said to have complained that the barrel was too short causing the riggings on the ship to catch fire when used. This resulted in the manufacturers extending the length of the barrel. The six carronades on board the Sirius were of the original short barrel design. Today, there are only five examples of this type of carronade existing in the world and two of them are on display in the Norfolk Island Museum. One was recovered from the wreck site in 1985 and the other underwent a very unique conservation process beginning in 1988.

Early Treatment
The initial conservation process was a method devised by Dr Ian MacLeod, Conservator, from the Western Australia Maritime Museum. Where as generally an object is first retrieved from the seabed and conserved on land, this conservation process began on the seabed. In 1988 a sacrificial anode was attached to the carronade in situ and electrolysis treatment began. The sacrificial anode is a metal object, generally zinc or aluminium alloy composition, which is electrically connected to the artefact via copper cable. In 1990 a storm detached the anode from the carronade and another had to be positioned that remained in place until 1993 when it was finally removed from the sea. Masses of concretion had formed around it after almost 200 years of being submerged.

The gun was taken ashore and placed in a caustic solution for eight months. The concretion was removed and a tampion (a plug) was found in the barrel of the gun that had waterproofed it and preserved it over the years. Chloride ion measurements were taken and proved the original seabed treatment had removed 80% of the ‘salt’; this was a terrific success. The gun was placed back into a mild caustic bath for a further two years until stable. The final process for the carronade conservation treatment was immersion in a 100 degree Celsius hot wax bath to remove moisture and seal it to prevent further effects from the environment.

Recent Treatments
The electrolysis treatment kept the carronade stable for approximately 10 years. Minor work was carried out on the surface in 2006 as a film of rust discolouration was penetrating the generally black appearance of the surface. The wax was removed and the surface was treated with an application of rust convertor/inhibitor and the area was resealed with wax.

Current Condition
The general condition of this carronade is good but close monitoring and cleaning is always a priority to maintain its condition.

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The carronade on exhibition at the Pier Store, Norfolk Island Museum

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Dr Ian McLeod with the tampion found in the barrel of the carronade (Norfolk Island Museum collection)

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Dr Ian McLeod with the tampion found in the barrel of the carronade (Norfolk Island Museum collection)

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Pulling the carronade out of the water (Norfolk Island Museum collection)

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Pulling the carronade out of the water (Norfolk Island Museum collection)

Bower Anchor

Museum Number:    NIM 7167
Other Number:    NI20
Material:    (Ferrous) Wrought Iron

Measurements:   
Weight:    1.7 tonne
Length of Shank:    4.62 metres
Length of Flukes:    1.75 metres
Span of Palms:    2.62 metres


In 1973 locals Ian Kenny, Peter Ely and others, freed one of the anchors. It was sent to the Western Australian Maritime Museum for conservation treatment in 1976 and returned to Norfolk Island in 1979. After returning from treatment it was placed on display in the Kingston area exposing it to winds and salt borne air. It remained outside until the Norfolk Island Museum was formed in 1988 providing a new inside home in a less vulnerable environment.

Early Treatments:
The anchor was de-concreted and painted on Norfolk Island prior to being sent to the Western Australian Museum’s conservation laboratory in Freemantle in September 1976. It was given electrolytic and dewatering treatment before being returned to Norfolk Island on an RAAF aircraft in March 1979. (Ref. Report to the Australian Bicentennial Authority on the December 1983 Preliminary Expedition to the wreck of HMS Sirius (1790) at Norfolk Island, Graeme Henderson, Curator, Maritime Archaeology,Western Australian Museum)

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The anchor on display at the Pier Store, Norfolk Island Museum

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Sending the anchor to Western Australia for conservation treatment by Royal Australian Air Force Hercules aircraft (Norfolk Island Museum collection)

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Sending the anchor to Western Australia for conservation treatment by Royal Australian Air Force Hercules aircraft (Norfolk Island Museum collection)

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Sending the anchor to Western Australia for conservation treatment by Royal Australian Air Force Hercules aircraft (Norfolk Island Museum collection)

Recent Treatments:
In 2008 an overlay was completed to record its current condition. This entailed taking colour photographs of each section of the anchor, and placing them onto a transparent sheet protector where colour coded markings identify where any corrosion, delamination, cracks or anomalies are showing. This process should be repeated in approximately 12 months to provide a comparison on the condition.

The anchor is made of wrought iron. The effect of corrosion on wrought iron resembles something like severely eroded timber; there are deep lineswhere the molten rods of metal were originally beaten together. These deep lines make cleaning and conservation treatments challenging. Every crevice of the anchor has to be treated and this means a labour intensive task using very small brushes.

Treatment was completed in sections. Firstly, the area to be treated was brush vacuumed, then brushed with methylated spirits. Secondly, a coating of corrosion inhibitor was applied and left to react and then removed with methylated spirits. Finally Senson Ferroguard sealant was applied. The end result was very pleasing and can be maintained by a regular cleaning program and controlling the environment.

Current Condition:
Prior to the recent treatment in 2008 the anchor was suffering from delamination in some areas and surface corrosion over the entire object. It appeared to be stable under the subtle lights of the museum however closer inspection with brighter lighting revealed otherwise. The anchor is generally strong and the condition is good except for a few areas, in particular on the arms where cracks have occurred. The Museum is in the process of constructing new supports for the arms. Once these are ready, the anchor will be lifted from its existing blocks, the areas that have been inaccessible will be treated and the anchor will come back to rest on its new supports.


Grape Shot

Sirius number:    SI 511
Materials:   
(Ferrous) Cast iron
Textiles – cloth and cordage
Embedded copper alloy sheathing tack

Grape shot consists of a number of iron balls (approx. 39mm) placed into a canvas bag with a central iron column that is attached to a base at the bottom. A rope is then tied around the bag giving it a quilted effect and a grommet is formed at the top to secure it and provide a loop for hanging or carrying. The recovered grape shot consists of 4 different materials made up of cast iron (shot), cloth and cordage and a copper alloy sheathing tack, partly embedded in a separated concretion. The concretion products formed on the cloth and between the iron shot are what keeps the form of the grape shot today. This is a very delicate object that requires extra care when handling.

Early Treatment
The grape shot was kept in salt water throughout the 1987 expedition and then transported to the Western Australian Maritime Museum for laboratory treatment. Conservation treatments are different for every material so it is difficult to determine the right conservation method for an object with multiple materials. At that time the grape shot was treated with a soak in liquid ethylenediamine for four months to release the iron corrosion products followed by a wash in acetone and vacuum drying. Finally a coating of Paraloid B 72 was applied to assist in consolidation of the artefact.

Recent Treatment
By 2004 the grape shot was showing signs of instability. Jon Carpenter of the Western Australian Maritime Museum states in the report "Conservation of the Sirius Collections Report for the Heritage Division of the Department of the Environment & Heritage and Norfolk Island Museum 2005", “ideally the grape shot should be separated into individual components/materials for selective conservation treatment. The integrity of the assemblage would be at risk but with due care it may be possible to begin the process by extracting shot from the underside of the structure. Stage by stage photographic documentation would be important to ensure that each component can be reinstated to its original position. The procedure would take several months and preferably should be carried out at a conservation laboratory capable of conserving the range of different materials. The stability of the artefact in its present condition is in doubt.”

This exhaustive procedure was not possible at this point so alternative treatments were carried out to improve its appearance and stability. These included removing loose corrosion products and treating the rust discoloured surfaces with corrosion inhibitor. A micro-environment was created by placing the grape shot in a glass cube. Inside were placed an oxygen scavenger to remove the oxygen and vaporphase corrosion inhibitor to remove the salt. It was then positioned on a padded support. Since then it has received further on-going treatments.

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Grape Shot

Copper and Copper Alloy Objects

Early Treatments
Initial treatment of most of the copper and copper alloy material involved the removal of corrosion products and coralline material through soaking in a solution of citric acid and thiourea. The citric will soften the unwanted corrosion products and the thiourea will prevent the acid from attacking the metal. A further soak in a sesqui-carbonate solution assisted in stabilising the artefacts by removing the chloride salts. Following this was a necessary soak in fresh water to remove the alkaline residue from the treatments. The objects were dried thoroughly and ‘Incralac’ was applied, this is an acrylic resin in acetone that provides a protective coating.

This nameplate underwent significant treatment. It is thought to be associated with Samuel King, private marine 50th (Portsmouth) Company. He travelled aboard the Sirius on the First Fleet voyage to Botany Bay. It is thought that as he stepped off the ship in Botany Bay he left behind his copper engraved nameplate. Samuel King then travelled to Norfolk Island on the Golden Grove in October of that same year where he settled and managed a grant of land until 1808 when he left Norfolk Island for Van Diemens Land.

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Samuel King nameplate after undergoing conservation treatment


Recent Treatments
Current treatment recommendations for the copper and copper alloy material in the Sirius collection are the same as the early treatments. Another chemical treatment to note was the use of alkaline dithionite reduction, to reduce the corrosion products and to assist in the removal of chlorides. This process offered the best chance of preserving any surface detail. The recommended sealant is now ‘Senson Ferroguard’ to provide the best protective coating.

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Spot test assessment on copper alloy objects to determine chlorides and carbonates, 2008 (Photographs by Karina Acton, International Conservation Services)

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Spot test assessment on copper alloy objects to determine chlorides and carbonates, 2008 (Photographs by Karina Acton, International Conservation Services)

 

Flagship of the First Fleet

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From the sixteenth century onwards the number of people convicted of crimes, many of which were seemingly trivial by today’s standard, was becoming a problem. The gaols in England were overcrowded, filthy and disease ridden resulting in many prisoners ...

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The World of Norfolk

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Norfolk Island was first brought to the attention of the rest of the world when it was discovered on a passage northwards from New Zealand in 1774 by James Cook, Captain of HMS Resolution. He named this tiny island “Norfolk” after “that Noble family”...

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Shipwrecked March 19, 1790

By about February 1790, both settlements in Sydney and Norfolk Island were running low on hardware including items such as blacksmiths’ tools, uniforms and eating utensils. In fact supplies were low of everything but food, which was adequate at that time.

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Artefacts Recovered

The Sirius carried four bower anchors and two stern anchors. Three of the bower anchors were recovered and one now dominates the Norfolk Island Museum’s collections. Two others are in Australia and one is still on the reef in a badly damaged condition...

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