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One of King Henry VIII's favorite warships was the Mary Rose, which served as one of the flagships of the English Navy for over 30 years, until she sank in a battle against the French in 1545. She made headlines again in 1982 when she was successfully raised from the bottom of the straits where she had lain for centuries, along with thousands of artifacts that have been a boon to maritime archaeologists ever since.
Conservationists have worked tirelessly to preserve the ship's remains and its many artifacts. And now high-energy X-ray analysis of chain mail links salvaged from the wreckage by a team of British scientists has revealed that the material composition of the armor is similar to modern brass alloys, according to a recent paper published in the Journal of Synchrotron Radiation. There were also traces of lead and gold, whose origin has yet to be decisively determined.
“This study clearly shows the power of combining sophisticated techniques such as those available at a synchrotron source,” said co-author Eleanor Schofield, head of conservation at the Mary Rose Museum in Portsmouth. “We can glean information not only on the original production, but also on how it has reacted to being in the marine environment and crucially, how effective the conservation strategies have been.”
An English rose
The earliest known reference to the Mary Rose appears in a January 29, 1510 letter ordering the construction of two new ships for the young new king: the Mary Rose and her sister ship, dubbed the Peter Pomegranate. (The Rose and Pomegranate ship badges are believed to represent Henry VIII and his first wife, Catherine of Aragon, respectively.) Once the newly built ship had launched, the young king wasted no time defying his advisers and declaring war on France in 1512. The Mary Rose served the monarch well through that conflict, as well as during a second war with the French that ran roughly from 1522 through 1525, after which she underwent a substantial overhaul.
Alas, the ship's luck ran out during yet another outbreak of war with France, leading to the Battle of the Solent, as French ships tried to land troops on English soil in the straits just north of the Isle of Wight. Along with the Henry Grace à Dieu, the Mary Rose led the attack on the French ships. On July 19, 1545, contemporary accounts report that the ship suddenly heeled over to the starboard side—perhaps due to a sudden shift in the wind—and the crew couldn't correct the imbalance. Because the gunports were open, water rushed in, sinking the Mary Rose. There were an estimated 500 men on board; fewer than 35 survived the sinking. The exact cause of the sinking is still a matter of heated debate, but it was likely a convergence of factors, including overloading, crew error, and that sudden gust of wind.
While the loss of the Mary Rose (and her crew) was a tragedy, the English ultimately won the battle, mostly by waiting out the French until the latter's supplies ran out. Henry VIII ordered an operation to recover the Mary Rose, but the retrieval technology at the time simply wasn't up to the task, although some rigging and guns were recovered. The wreck was eventually forgotten, until it was rediscovered briefly in 1836 when some of the timbers were exposed by shifting tidal patterns and caught the attention of local fishermen. It was rediscovered again in 1971, sparking a modern excavation and salvage mission over several years.
By 1982 there had been enough irreversible damage to the structure that plans were made to recover the Mary Rose as soon as the diving season was over that year. Raising the ship was no small feat, given that only roughly a third of the structure was still intact, embedded in mud. The hull was emptied of any artifacts and outfitted with steel braces to ensure it didn't fall apart while being raised. Prince Charles was among the spectators on October 11, 1982, when the Mary Rose was finally lifted out of the water and safely to the shore.
Preserving the past
For many years, the hull was housed in a covered dry dock as conservationists worked to preserve the structure. That required keeping the entire thing saturated with water, initially, and then a polyethylene glycol solution, followed by a period of controlled air drying. It was still open to public viewing during those years, albeit from behind a glass barrier. The ship is now displayed in the official Mary Rose Museum, built right over the original dry dock in Portsmouth.
The museum is also home to over 26,000 artifacts recovered from the shipwreck, including pieces of timber, casks for food and drink, chests, sundials, a backgammon set, tools for navigation and woodworking, several musical instruments, weapons, surgical tools, the skeletons of all those lost crew members—even the skeleton of a “ratter” dog named Hatch brought on board to keep the rat population at bay.
Many of the artifacts had been well-preserved by the silt in which they were buried on the ocean floor. That was certainly true of the chain mail links analyzed for the current study. But additional preservation measures were nonetheless necessary. The links used in the study—two were twisted loops of brass wire, and the other was three linked flat washers that appeared to be made of copper or copper alloy—had each undergone different cleaning and/or anti-corrosion treatments just after recovery (distilled water, a benzotriazole solution, and ultrasonic cleaning), making for a useful comparison of the effectiveness of the methods used.
The British team used the XMaS (X-ray Materials Science) beamline at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, to examine the surface chemistry of the links. Synchrotron radiation is a thin beam of very high-intensity X-rays generated within a particle accelerator. Electrons are fired into a linear accelerator to boost their speeds and then injected into a storage ring. They zoom through the ring at near-light speed, as a series of magnets bend and focus the electrons. In the process, they give off X-rays, which can then be focused down beamlines.
This is useful for analyzing structure, because in general, the shorter the wavelength used (and the higher the energy of the light), the finer the details one can image and/or analyze. The team found that the links were made from an alloy that was 73-percent copper and 27-percent zinc. According to co-author Mark Dowsett, emeritus professor at the University of Warwick, this is “quite a modern alloy composition,” but what was surprising was the level of control.
“We had three completely different samples, and the analysis was the same,” he told Ars. One sample had been thoroughly cleaned, but the others had not, and thus still had a corrosive layer. Yet all three showed the same composition ratios. This suggests that Tudor England was fairly advanced in brass production and techniques like wire drawing.
The analysis also revealed heavy metal traces, including lead and gold, on the surface of the links. According to Dowsett, it's possible many of those traces came later, since during World War II, the Portsmouth Dockyard was the target of heavy bombing, depositing lead, mercury, and cadmium, for instance, into the Solent waters. “You can imagine that the armor sank to the bottom of the sea and gradually corroded, and then it picked up the stuff from the seafloor afterwards,” Dowsett said. Alternatively, the lead may have been from dust produced by the lead balls used in 16th-century scatter guns and pistols.
As for the gold, traces were only found on one set of links, and he thinks it likely came from the tooling when the armor was made, rather than mixed into the brass alloy. “Gold is very soluble in brass, so if you added gold to the alloy, you would never see it as a separate material,” he said. “We saw crystalline gold. That tells you there are pure gold particles on the surface that presumably came from tooling used to work the pieces the armor was made from.”
As for the different conservation methods applied to the three artifacts, “Overall, the measurements confirm the effectiveness over three decades of the different storage arrangements and conservation treatments applied to these artifacts,” the authors wrote. “This knowledge can inform the conservation strategies employed when treating such materials from a marine environment.”
One helpful recommendation for future studies is to protect the samples a little bit more by lowering the X-ray dosage, and perhaps even blanketing artifacts in helium to guard against further damage. “X-rays passing through the air, which these are doing, generate ozone and nitrogen dioxide, both quite aggressive gases,” said Dowsett. “Ozone is a strong oxidizing agent and nitrogen dioxide will instantly dissolve in any water vapor to form nitric acid.” Blanketing the surface of a sample in helium effectively removes that risk.
The team also managed to achieve extraordinary sensitivity with their approach. “X-ray diffraction doesn't normally give you a sensitivity of a few parts per million, but because of the intensity of the synchrotron beam, and the fact that we took data from thousands of camera pixels and put it into one data point in the diffraction pattern, means that we achieved a superb signal-to-noise ratio,” said Dowsett. That translates into the ability to use a smaller dose of the powerful X-ray beam, as well as processing samples one hundred times faster. Since time on a synchrotron is expensive (as much as $10,000 per day), that also means reduced costs.
“It is fascinating to examine ancient technology using specially developed analytical methods which can then be applied to modern materials, too,” said co-author Mieke Adriaens of Ghent University of her involvement in the project. “It was also a real privilege to be allowed access to these unique artifacts and to play a part in unravelling their story.”