H.L. Hunley is finally coming out of her shell

In August, scientists at Clemson’s Warren Lasch Conservation Center began removing the hardened layer of sand, shell and sediment that has encased the Hunley’s hull for more than a century. They have finished more than 70 percent of the sub’s outer surface.

The H.L. Hunley doesn’t look nearly as old as she once did.

Amazing what a face-lift can do.

Clemson University scientists have spent the past four months scraping away a heavy layer of encrusted sand, sediment and shell from the hull of the Civil War submarine that built up over the 136 years it lay hidden beneath the Atlantic floor.

Now, for the first time in more than 150 years, the Hunley’s bare skin is visible. And its iron hull doesn’t look that much older than, say, the Cold War-era sub Clamagore.

In fact, the results of the Hunley’s deconcretion so far are picture-perfect, which means the sub looks exactly as artist Conrad Wise Chapman depicted it in an 1863 painting.

“Chapman was extremely precise,” said Paul Mardikian, senior conservator at the Warren Lasch Conservation Center. “It’s as if we have been looking at a fuzzy image and are just now getting the picture in focus.”

Just as in the Chapman painting, the Confederate sub appears to have been mostly black — the natural color of iron in water. The sub was not painted, but Mardikian said there is some evidence of a coating probably used to waterproof the hull, which has dozens — if not hundreds — of seams where pieces were fitted together.

Mardikian hopes this clear look at the Hunley’s hull will provide archaeologists with some insights into the sub’s construction, adventures and eventual sinking. But they are just now beginning to uncover the sub’s “forensic hot spots,” as he calls them.

The Hunley is made of two different types of iron — cast and wrought. Cast iron is made from molds while wrought iron is heated and worked with tools. Cast iron tends to be more brittle. The main hull is exclusively comprised of wrought iron, and that is the 70 percent of the fish boat now visible.

The biggest discoveries so far are two dents just below the sub’s dive fins, which may be damage incurred during recovery efforts the first two times the Hunley sank in Charleston Harbor.

They’ve also found the letters “CN” stamped into the iron. Right now, scientists assume the letters are the mark of the foundry where the iron was forged.

The most startling revelation is how much damage the unforgiving sea inflicted on the sub. The starboard side of the boat has been heavily sanded down by years of saltwater currents running along its side. Two holes in the sub’s starboard side were almost certainly caused by these vicious currents running along the hull.

Like an eraser, this erosion may have wiped away important evidence that could explain what caused the sub to sink in the winter of 1864.

Now, Mardikian and his team are moving on to the cast-iron pieces of the sub — its bow, stern, keel blocks and two conning towers. These are the places they expect to find more detailed information about the Hunley.

Wrought iron does not retain its surface as well as cast iron, which is more likely to preserve the fingerprints of history. But cast iron is also more fragile. The scraping of these pieces will be much more delicate and time-consuming.

“There is no room for error for working on a one-of-a-kind artifact like the Hunley,” said Nestor Gonzalez, associate director of Clemson’s Lasch Center.

The trick, Mardikian explains, is to not do any damage to the historical record imprinted on the hull. Where the concretion ends and the iron begins is sometimes hard to detect.

“You have to be careful that you are not removing something you are trying to preserve,” Mardikian said.

The forward conning tower will be the most nerve-wracking work of all. Testimony from the crew of the USS Housatonic, which the Hunley sank on Feb. 17, 1864, suggests that the Union sailors fired dozens of small-arms shots at the sub, concentrating mainly on its cast-iron forward conning tower.

Conservators wanted to hone their deconcretion skills on the sturdier wrought iron, and now will move on to the more delicate work of scraping the cast-iron pieces. Mardikian has already started working on the sub’s bow.

In the coming weeks, the crew will move to that forward conning tower. There, they could learn what caused the only port-side hole in the sub, or they could come away no closer to answering the question that has perplexed Civil War historians for 150 years.