Hunley to undergo first soak in conservation bath

  • Thursday, May 8, 2014

The 76,000-gallon holding tank the Hunley rests in will be filled for the first time with a chemical solution designed to save the fragile iron submarine from deterioration. During the Civil War, the Hunley made history in 1864 with the sinking of the USS Housatonic. Shortly after the attack, the submarine's crew signaled to shore they were on the way back to land, but then instead, mysteriously vanished without a trace. She remained lost at sea for more than a century, until an expedition funded by author Clive Cussler discovered her location in 1995.

Scientists have been working to excavate and conserve the Hunley since she was recovered from the ocean floor in 2000. This first soak in a conservation bath marks a major milestone in the efforts to save the legendary submarine. The salts in ocean water are like poison to metal. These salts permeated the Hunley's iron skin during her 136 years at sea, leaving her at risk for corrosion and disintegration if they are not removed.

“Today is a very big day and a major advancement for our work. Losing an artifact as historically important as the Hunley is simply not an option. Conserving something this large and complex has never been done before and it took years of planning to get us to this point,” said Nestor Gonzalez, assistant director of Clemson University's Warren Lasch Conservation Center.

The tank will be filled with sodium hydroxide, a chemical solution designed to leach out the salts threatening the submarine. This will be the Hunley's first of many long soaks in the chemical bath and should last about three months. The goal of the first bath is mainly to loosen up the rock-like layer of sand, sediment and rust, often referred to as concretion, that built up slowly over time around the submarine. Concretion currently coats the entire vessel and, in some places, is harder and stronger than the actual iron it covers. Scientists must carefully remove the layer of debris because it inhibits the effectiveness of the conservation treatment from leaching out the salts.

Chipping away the concretion is a necessary step in successfully conserving the Hunley, and those working to solve the mystery of her disappearance are hopeful it will also yield valuable new clues. It has been very difficult to conduct their investigation when they have not been able to view and study large portions of the submarine since it has been covered with this substance. The concretion could very possibly be masking critical data. For example, historical records indicate the Hunley was spotted by the enemy and fired upon shortly before her attack. During the removal process, scientists could uncover bullet damage that may have impacted the Hunley's ability to return that night. Or, they could find countless other clues and evidence that will shed light as to why she vanished.

“This will be an exciting phase for the project. We will be able to see the true surface of the Hunley for the first time. Chiseling away the concretion will allow us to travel back in time, potentially helping us learn what happened to the Hunley and her crew that night,” said Hunley Commission Chairman and Lt. Governor Glenn McConnell.

The tank will be drained for short intervals, allowing scientists time to remove the debris material covering the submarine. The process of removing the concretion is expected to last approximately a year and then the Hunley's conservation treatment can begin to take full effect. The submarine will continue to soak for the next five to seven years in the chemical preservation solution, which experts say will need to be replaced every three or four months.

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