Scientists remove concretion (Photos courtesy of Friends of the Hunley)





Scientists chiseling away decades of sand and shell from the H.L. Hunley are forging a tie to the builders of the historic submarine: A painstaking attention to detail.





Since August 2014, a team of conservators using small tools, including dental chisels and hammers, have been removing concretion coating the exterior.





They are looking for clues as to why the Hunley sank after it became the first submarine to sink an enemy vessel.





“It keeps surprising us,” said Nestor Gonzalez, assistant director of Clemson University’s Warren Lasch Conservation Center in North Charleston, S.C.





“ You have a very close sense of the attention to detail and the care they put into it," he said. "How the rivets are perfectly flush and the finishing is very high quality.”





Three days a week, members of the team enter the drained tank, wearing protective eyewear, gloves and masks as they slowly reveal the doomed submarine’s skin.









That work is adding to their knowledge of the craftsmanship that went into the Hunley, which was built for the Confederacy in secret in Mobile, Ala., without the use of blueprints.





Scientists have been looking for any separation of the wrought iron plates that cover the exterior. Such a discovery would indicate the Hunley may have suffered fatal damage when the USS Housatonic went off. torpedo it planted into the hull of the Union shipUSS Housatonic went off.





“We have not seen anything like that,” Gonzalez recently told the Picket. “The guy was a very good builder.”





What the team is finding is a vessel that, while corroded, retains its structural integrity. The builders staggered the plates to strengthen their hold and carefully connected the rings that form the skeleton of the 40-foot Hunley.





“Everything had been very well thought out,” said Gonzalez.





Conservator Virginie Ternisien at work





The stuff of legends





The Confederate government brought the Hunley to Charleston in a bid to help break the Union’s siege on the port city. The eight-member crew that set out for the Housatonic knew the risks.





Five members of the first crew died in August 1863 when it accidentally dived while its hatches apparently were open. The second crew's eight members succumbed in October when the Hunley failed to return to the surface.





On the moonlit evening of Feb. 17, 1864, the crew of the hand-cranked vessel set off a charge that sent the Federal vessel to the sandy bottom outside Charleston Harbor.





Hunley – likened to the shape of a whale -- disappeared from view. What happened to it has become the stuff of legends and research for decades. TheHunley – likened to the shape of a whale -- disappeared from view. What happened to it has become the stuff of legends and research for decades.





For a long time, one prevailing view held that a lucky shot broke the glass in one of the Hunley’s portholes, bringing in rushing water and causing the sub to sink. But research has not proven that theory.





a 2014 article about the project. Another scenario holds that the Hunley was swamped by or struck by another Union vessel. Or that it plunged to the sea floor to avoid detection, and never made it back up. A latch on the forward conning tower was found to be not properly locked, adding to the mystery, CNN reported inabout the project.









In January 2013, officials announced a significant discovery.





Research showed the submarine was less than 20 feet from her 135-pound torpedo when it exploded. The effects of the blast may have sent the Hunley to the bottom, where the crew ran out of oxygen.





Ongoing efforts to solve the mystery





Conservators have been looking for any holes or bullet damage that may help explain why the Hunley sank.





“There is nothing we can see at this point, said Stephanie Crette, director of the Lasch center.





The vessel appears intact.





“We are stabilizing the items, but also working to unveil the secrets of the submarine. We are moving toward finding evidence as to why it sank,” added Gonzalez. So far, there are “no new clues.”









Removing the sediment from the Hunley is a critical component in understanding its construction and what happened.





Last May, scientists immersed the submarine in a bath of toxic sodium hydroxide to help loosen the concretion. The idea is to loosen the sediment, remove as much salt as possible from the wreckage and help protect it from further corrosion.





The scientists work from about 8 a.m. to 2 p.m. on Tuesday, Wednesday and Thursdays after solution is drained from the tank and the pH level is lowered, said Crette. The tank is refilled each day when their work is completed. Analysis is done on other days. (The general public can see the Hunley on weekends).





In some areas, the concretion can be up to two inches deep. The team works in a grid fashion, first exposing the rivet line and then working their way to the center of the plates.





Next up: Hunley’s interior





Scientists have completed cleaning nearly all of the exterior plates and are moving on to cast iron components – a very long and complicated process.





We are seeing absolutely outstanding surfaces.” “Cast iron is very difficult,” said Gonzalez. “But it is also very rewarding …









“It can reveal fantastic details,” said Gonzalez. Builders used cast iron for the dive planes, the conning towers and for parts of the bow and stern. Conservators are excited about exploring the connection that linked the torpedo spar to the hull.





Officials said they have found no evidence indicating a problem with forward conning tower may have had anything to do with the Hunley’s demise.





Scientists expect to begin deconcretion of the interior in about three months, with the entire process completed by the end of the year.





While the Hunley submarine is empty, there’s a possibility that an artifact may break loose during the work, Crette told the Picket. One scientist found an entire snail shell in the encrusted exterior.





Paul Mardikian works on the bow.





With the chipping away of each piece of crust, the submarine is returning to its original appearance, the conservators guided by an 1863 painting of the Hunley by Conrad Wise Chapman.





Friends of the Hunley The nonprofit provides a history of the boat and current conservation updates on its website.





“A lookout aboard the Union Navy's largest ship was tired, cold -- but restless. Talk of a Confederate secret weapon was in and out of his thoughts. Suddenly he spotted something move in the chilly waters. A porpoise? There were certainly a lot of them around. But something about this one didn't seem right."





What didn’t seem right was the Hunley, which sank the Housatonic. Five of its crew members died; 150 others were soon rescued.





The eight men on the Hunley also died. The quest continues for the manner and cause of their deaths.



