On the 11th October 1982, the hull of the Mary Rose was lifted from the seabed on a supporting steel cradle. After it was raised, the ship was covered in water-saturated foam and sprayed with seawater to keep the timbers from drying out, cracking, or changing dimensions from an uncontrolled loss of water.
In December 1982 a building was constructed around the hull. Inside this, the ship was sprayed with recycled, refrigerated, filtered, fresh water to stop it from drying out and prevent microbial activity. Spraying also helped to remove some of the salts and dirt from the timbers so to aid future chemical impregnation.
Without spraying, the wood could have shrunk by anything up to 50%, warped and cracked as the water evaporated from its cellular structure.
Before the ship was lifted, it was emptied of many timbers which were not securely attached. These structures had been mostly held together with iron fastenings, which had corroded underwater.
More than 3,000 loose timbers were removed from the ship and placed into wet storage. Many of these timbers were eroded beyond recognition, but around 700-800 were in good enough condition that they could be reunited with the ship before the conservation treatment began.
Between 1989 and 1993 the loose timbers were put back in place. In 1993, the decision was made that not all of the ship timbers could be placed back as the structure was not strong enough to support the extra weight.
The part of the ship that was recovered, the starboard side, was protected from being attacked, by shipworm and gribble, or from being eroded away by the tides and currents, by a ‘blanket’ of organic rich silts on the seabed. The silt cut off the oxygen, creating an environment in which sea creatures can’t survive. However, some bacteria can thrive in areas without oxygen, and these bacteria ate away at microscopic parts of the cells of the wood, leaving only a weak skeleton structure which then filled with sea water.
Polyethylene glycol treatments (PEG) were chosen by the conservation team as the best approach to filling the microscopic voids within the wood in order to stabilise the ship. PEG was selected because of the success of this resin in the historic treatment of waterlogged wood, including the treatment of the Vasa (17th-century Swedish warship). PEG would consolidate the timbers by filling the voids and lumens of degraded and weakened cells within the wood.
It was decided that the ship could not be submerged in PEG due to the economic and practical costs of building a tank big enough to hold it. Instead, spraying the ship with PEG was considered the most effective method for covering all the timbers.
Phase one of the conservation treatment began on 30th September 1994 and continued until 2003. A low molecular weight PEG was sprayed all over the ship to fill the less degraded inner parts of the timbers. A circulating spray system was constructed in the museum which would collect the sprayed PEG and reuse it to continue the spraying process. This system consisted of 522 metres of pipework and 315 nozzles around the ship. Around 40,000 litres of PEG were sprayed onto the ship each day. 2004 to 2013 saw Phase Two of the conservation treatment; the ship was sprayed with a higher molecular weight of PEG. A higher molecular weight was needed to increase the mechanical strength of the wood, reduce the risk of cellular collapse and seal in the lower molecular weight PEG.
In 2013 the third stage of the conservation treatment could commence; the ship carefully began to be dried. A plastic box was built around the ship to create a smaller air volume which would require less energy to heat. Within this giant ‘hot box’, an air-drying system was installed to provide consistent air temperature, relative humidity, and velocity to all parts of the hull. This system had been set up while the PEG spraying was still in progress so that there was no significant wait between turning off the sprays and turning on the air-drying system.
The conditions were kept at around 55% relative humidity and 20 degrees Celsius. These conditions would limit the dimensional movement of the timbers caused by the loss of moisture. It is estimated that over 100 tonnes of water were removed between 2013-2016. Additional scaffolding was put onto the ship as it experienced slight shrinkage. During drying, core samples were taken from the timbers to determine the change in moisture content.
By May 2016, the ship had dried enough to allow the drying ducts to be removed. These were replaced by air diffusers, which were placed around the hull without obstructing the view, and the hot box was dismantled.
During all the phases of conservation the ship has been monitored for movement. In 1983, just after the raising, different markers were placed on areas of the ship and measured regularly to see if movement was taking place. Additional markers have been added over the course of the conservation work and are measured annually. While the ship was being dried a total station was installed to monitor the ship. This is a laser-based device which measures the distance between it and the targets around the ship. The total station takes measurements three times a day. The ship has also been laser scanned several times.
From 2016 to the present day, the ship has been kept in an environment of 55% relative humidity and 19º Celcius. Pest traps have also been introduced into the Ship Hall to monitor insect activity around the ship. Every summer the ship is cleaned using vacuum backpacks and soft bristle brushes to remove dust that can fall from the visitor gallery on the Upper Deck of the Museum.
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