BRUNSWICK COUNTY — Brunswick Town/Fort Anderson State Historic Site is now conserving a big chunk of history. Iron, to be exact.
About a dozen visitors to the historic site on Thursday caught a glimpse of the first moments of electrolysis conducted on a Colonial-era cannon. A dredging company under contract with the U.S. Army Corps of Engineers pulled it from the Cape Fear River in late December.
After was picked up by the dredging crew, the cannon — believed to be from the early 1700s — was stored for a couple weeks until it was off-loaded, wrapped in burlap, and made its way to Brunswick Town/Fort Anderson State Historic Site on Dec. 20, according to Site Manager Jim McKee.
McKee also announced in December, that the cannon would undergo conservation at Brunswick Town/Fort Anderson, the first of its kind to take place at the historic site.
McKee has worked closely with archaeologists in the State’s Underwater Archaeology Branch through the course of the project, including the electrolysis process, which now in its early stages.
“The first minutes of conservation of an old cannon — It’s exciting. It really is,” McKee said. “This is something everybody has been waiting for … now, we wait at least a couple years.”
Visitors to the site on Thursday were also excited about the cannon and the process; some even got to touch the cannon one last time before it was submerged in water with a bit of sodium hydroxide added to the tank.
The conservation process is all science, said Nathan Henry, assistant state archaeologist with North Carolina’s Underwater Archaeology Branch, which is within the N.C. Department of Natural and Cultural Resources. Prior to being submerged in water, Henry worked to hook up the source of electricity to the artifact for the electrolysis.
Using wires to generate a negative electrical current through the cannon and a positive electrical current through two long pieces of steel running along the walls of the tank, on either side of the artifact – known to archaeologists as the cathode and sacrificial anode, respectively – they begin the process of removing salt from iron cannon, that has built up over hundreds of years.
Henry said just a small amount of electrical current is used, less than 1 amp.
“We’re creating a salt magnet,” Henry explained. “What we’re doing is trying to get the salt out of it. It’s been sitting down there in the salt water and anytime a piece of iron like that sits in salt water, it absorbs the salt. That salt, when it crystallizes it will cause it to swell up, and start falling apart. The metal on the sides will absorb the salt that’s inside this gun.”
Archaeologists can measure the amount of chloride (salt) in the solution (electrolyte) in the tank, each time hoping for a diminished chloride level. Once no chloride can be measured in the liquid, the process is complete. Distilled water is also sometimes used in the final step of the process.
The goal of the electrolysis, is to restore the iron within the cannon, which will keep the cannon from rusting and thus corroding over time. The process is similar to what Henry has used on other cannons, including cannons he’s worked on from the Queen Anne’s Revenge.
Once the electrolysis is complete, they’ll begin chipping away at the concretions on the cannon, layer it up with Tannic acid to keep the iron from rusting and finish it off with wax, similar to what’s used for surf wax. Though little is known about the cannon, once the concretions are removed, Henry and McKee could discover a “maker’s mark” on the cannon that could tell more about the history of the cannon.
What’s next for the cannon?
So far, archaeologists have determined the cannon measures 93 inches long with an 80-inch bore and is 4-inches in diameter. The cannon also has a break at the end of the muzzle and is similar to some of the six-pound English guns that were found on the Queen Anne’s Revenge.
Interpretation panels will be installed with the cannon, for people to learn more about the cannon and its conservation process. McKee also said the cannon project is also a great STEM education tool for students.
“Not only is it an artifact that is going on display, but the learning – the education – we can do while it’s in this tank is phenomenal,” McKee said. “We already do that, but this is just something added. It’s a new interpretation we can do. A new education tool for the guests.”
The cannon will remain at the site for observation and study. Visit Brunswick Town/Fort Anderson State Historic Site to see the cannon, Tuesday through Saturday from 9 a.m. to 5 p.m. For more information about the historic site visit its website or follow it on Facebook.
Watch the first moments of conservation: