Science innovation at the Mary Rose

Materials World magazine
,
24 Sep 2018

Khai Trung Le talks to Professors Serena Corr and Eleanor Schofield on the scientific innovations used in the restoration of the Mary Rose.

The prevailing theory surrounding the end of the Mary Rose, Henry VIII’s flagship for 34 years, is particularly ignoble. During the 1545 Battle of the Solent, the Mary Rose is believed to have left its gunports open when a sudden gust of wind tipped the ship. It flooded and quickly floundered from the excess weight of additional cannons and manpower, and hit the seabed with such force that, when the hull was discovered more than 400 years later, the keel was 3m below the Solent floor. After three decades of sailing, so fell the flagship of one of the most powerful kings of England.

Fortunately, the seabed also helped partially protect the ship for four centuries. The Mary Rose was discovered in May 1971 and raised in 1982. Since then, the Mary Rose Trust has undertaken extensive restoration and preservation efforts, and while science is an integral part of any conservation effort, the trust, under Professor Eleanor Schofield, Head of Conservation and Collections Care, has specifically championed and placed scientific innovation at the fore of their work.

Historic attraction

Most recently, the trust has seen success in the use of magnetic nanocomposites in extracting iron ions that could form destructive acids in the ship’s hull. Iron sulphide, formed from migrating sulphur-reducing bacteria while the ship was submerged, and reacting with
iron ions from corroded metal fixtures, is present within the wood. While stable in low-oxygen environments, when in air and in the presence of iron, sulphur oxides form destructive acids.

When the hull was raised from the seabed, it was routinely treated with a cold-water spray and polyethylene glycol to replace the water in the cellular structure of the wood and improve structural integrity. However, since stopping the treatment in 2013, as the trust sought
to dry the wood in controlled conditions, there is increased risk of acids forming.

Professor Serena Corr, Chair of Energy Materials at the University of Glasgow’s School of Chemistry, UK, told Materials World, ‘We’ve been working on how the nature of iron and sulphur changes as a function of drying using techniques such as X-ray absorption spectroscopy at Diamond Light Source. We’ve seen how sulphur present within the wood undergoes oxidation as a function of drying, and we’ve been able to correlate these observations with areas of degradation within the Mary Rose.’

Following their analysis, Corr’s team has designed magnetic nanocomposites primarily comprising magnetite and porphyrin in a thermoresponsive polymer. The nanocomposite can be applied as a gel before, at lower temperatures, taking a liquid form to infiltrate the wood. The magnetite attracts iron ions, which become sequestered within haems in the porphyrin particles, and the polymer is extracted before
it is heated and reconstituted into a gel form once again, for collection.

Corr said, ‘Our nanocomposites have been tested on fresh oak samples, the same wood used to build the Mary Rose, to check the efficacy of binding and removing any free iron trapped within the
wood. Now our work is focused on treating samples from the Mary
Rose timbers.’

The nanocomposites are highly tuneable, not only for use on other historic artefacts, but with potential for wider applications. Corr continued, ‘These sorts of materials are widely used in bio- and nanotechnology. Porphyrin molecules are also used in cancer treatment – you could envision a case where nanoparticles are used in hyperthermia, where the nanoparticle takes up a cancer cell and localised heating destroys it.’

One down, 18,999 to go

With around half of the hull and some 19,000 artefacts recovered, the trust has embarked on numerous collaborations to help monitor and preserve the Mary Rose. Schofield has been instrumental in raising the profile of scientific fields in the trust’s activities. She told Materials World, ‘That’s part of the reason I was hired. I didn’t have a conservation background, but the trust knew I would push the scientific agenda. We believe you need both.’

The trust gained a degree of notoriety in March 2018 from the decision to opt for destructive testing in determining corrosion to a number of recovered cannonballs. Schofield said, ‘Conservators were monitoring and noticed cracking and damage, and we made the decision to take them off display. I developed a project with University College London, UK, and Diamond Light Source to investigate, and we chose destructive testing. My feeling was we have 1,200 cannonballs, and if we did nothing, I think that’s more negligent than taking a few and developing treatments.’ Although it was reported that 12 balls were sent for destructive testing, Schofield stated that ‘others had already gone through treatment and were in pieces in a bag. In reality, it was about half as much’.

A current project between University College London (UCL) and the National Physics Laboratory (NPL), UK, is exploring the museum environment and the effects of combining exhibits. Schofield said, ‘The museum is an immersive environment, and we have materials in the same cabinet to tell a better story. But some materials give off gases that could potentially harm other materials.’ The UCL/NPL team is observing the environment and impact of gases on wood and metal artefacts, and developing sensors to monitor the status of exhibits.

Other projects include finding alternative ways to monitor sulphur in wood, given that many museums will not have access to synchrotron technology or experts on staff, radiography tests measuring moisture content and wood drying rates, and laser scans of the Mary Rose to
help predict future concerns. Corr referred to the Mary Rose as ‘a scientist’s dream’, and Schofield made note of the enduring need for scientific innovation, saying, ‘We’ve answered some questions, but created many more.’

Lucifer alone

The tyranny of Henry VIII – a man so petulant that when the last Catholic Archbishop of Canterbury, Reginald Pole, said of Henry, ‘Lucifer alone may fitly be compared to thee,’ his response was to have Pole’s 80-year-old mother brought to London and executed – was not unnoticed by Corr.

Corr, who will soon join the University of Sheffield, UK, as Chair of Functional Materials in the Departments of Chemical and Biological Engineering and Materials Science and Engineering, said, ‘I push this a lot, in the days of Brexit, but it’s a really multidisciplinary, multinational project. I’m Irish, Schofield is English, we’ve an Indian postdoc, and a Spanish PhD student. We’ve worked with the University of Copenhagen, the Netherlands, and Columbia University, USA. It tickles me to think what Henry VIII would have made of all these different nationalities working on his flagship. Let alone a woman!’