The high-pressure business of historic preservation at Clemson’s Warren Lasch Conservation Center
NORTH CHARLESTON, South Carolina — Father time has always been a tough opponent. But Clemson University researchers are giving him a run for his money. For the past several years, a Warren Lasch Conservation Center team in North Charleston has come up with an innovative way to restore historical metal artifacts’ original luster.
By using the same technique city employees in the United Kingdom have been using for years to restore masonry and remove graffiti from historical buildings, the Clemson conservators now are able to undo many of the effects of time on artifacts like Civil War-era cannons and other warship guns.
They have adapted a process that originally was designed to work on concrete and other stone to work on metal using a device called a ThermaTech unit.
“Think of it as using a really fancy pressure washer,” Lasch center Executive Director Stéphanie Cretté explained, “but instead of liquid water it sprays out steam.”
The ThermaTech unit Cretté and her team began using in 2013 looks a lot like a generator on wheels with an external pump capable of an output of up to 8.5 liters per minute, pressures of 160 Bar (2,320 psi) and temperatures of 302 degrees Fahrenheit.
“That’s just a fancy way of saying it’s really powerful,” she says with a laugh.
Until recently, metal conservation methods had involved abrasive blasting, having to move the artifact offsite and using hazardous chemicals. That process was really expensive. But now, with this new approach, the process is non-abrasive, can be done onsite, uses regular tap water and is comparatively inexpensive.
Once they are done using the ThermaTech on an artifact, Cretté and her team – assistant conservator Christopher McKenzie and historic preservation specialists Justin Schwebler and Claire Achtyl – treat it for corrosion, let it dry and put on a final coating. It’s this coating that protects the artifact while making it look close to what it looked like when it was first made.
The entire process takes anywhere from a few months to several years, depending on the object and its size and the conservation treatment plan to be followed.
“I’d definitely say it’s a complete game-changer,” said Dawn Davis, public affairs officer for Fort Sumter National Monument and the Charles Pinckney National Historic Site, one of the many clients with which Clemson has been working.
“In the past, sandblasting had been the primary method of restoration, but with this new technique Clemson uses, we’ve actually found additional layers on some of the guns. It’s neat to see some of the writing that had never been noticeable before. It allows us to learn even more about the history we’re trying so hard to preserve.”
The Lasch center has used this process to restore several important artifacts:
- Several U.S. National Park Service projects at Fort Moultrie on Sullivan’s Island and Fort Sumter in Charleston Harbor, where they are focused on outdoor ordnance and metallic architectural elements.
- A six-inch, .30-caliber gun from USS Maine, an American naval ship that exploded and sank in Havana Harbor during the Cuban revolt against Spain in 1898. (See related article about the restoration of the gun from the USS Maine.)
- Three cannons from the CSS Pee Dee, a Confederate gunboat launched in 1865 and scuttled the following month during the Civil War. The cannons include two from the Confederacy and one from the Union.
The Warren Lasch Conservation Center is a 45,000-square-foot facility at the former Charleston Naval Base. It houses state-of-the-art equipment from electron microscopes to three-dimensional scanners. The tank room contains a 90,000-gallon tank with two 20-ton cranes on rails where research and conservation is conducted on the 1860s submarine H.L. Hunley. Currently, the Lasch center scientists are the only ones in the United States using the ThermaTech process, making them the go-to group for metal restoration.
“It’s quite the feather in our cap,” Cretté said, “and we keep honing the process and getting better with it every day.”
“The best part,” Davis of the National Park Service said, “is they don’t just do the work and then leave. The Clemson scientists take the time to teach us about what they’re doing so we can better care for the artifacts. They are very willing to talk to the public and share what they’re doing. It’s a really good partnership.”