A concretion exterior and an x-ray that shows what may be an African currency called a manilla in the concretion.
Credit N.C. Department of Cultural Resources
New software may help remove some of the mystery from items slated for preservation for conservators at Greenville’s Queen Anne’s Revenge Conservation Lab. George Olsen has more.
Dive teams have been bringing up artifacts from a Beaufort Harbor shipwreck believed to be the Queen Anne’s Revenge, the flagship of the pirate Blackbeard, since 1997. Many objects recovered were initially concreted, a hard dense crust that forms around an iron object as salt water causes iron to rust. Sitting on the ocean floor since 1718, items have concreted to a point where a few objects are easily recognized, most aren’t.
“Most objects that come up aside from the cannons and anchors which have a very diagnostic shape come up as an amorphous blob, and there’s no way by looking at something to tell what’s inside of it. That’s why the x-rays are so important to our task here because that helps us decide what’s inside it and what needs more conservation attention or what is more diagnostically interesting for the archeologists to study.”
Kim Kenyon, a conservator at the Queen Anne’s Revenge Conservation Lab in Greenville. To date, those x-rays have been two-dimensional pictures. But in approaching how to free the items inside their concretion, 2-D images have their limitations.
“You have 3 different objects set in one concretion, you can’t tell by looking at a two-dimensional film which one is closer to the surface or which one is deeper within the concretion or whether or not its touching, things like that. That kind of information is what we’re hoping to learn from the 3-D technology.”
This summer members of the physics department at Davidson College will use Digitome software to give conservators like Kim Kenyon a better handle on just what it is they’re trying to preserve.
“The difference is it’ll be shot on a digital film and so we’ll shoot several different angles of the same object, and then using a computer program we can stitch together those digital images to give us a 3-dimensional representation of that object. And that helps us because many times the concretions are conglomerates of one or more objects. We have a few concretions that have several hundred individual artifacts in them. What the 3-D x-ray can tell us is how those items are spatially related to each other before we start trying to break up the concretion. That’s not something we can tell from a 2-dimensional x-ray film.”
That detail will help in the cleaning of the artifact. Kenyon says clearing an item of concretion is not that long a process, if you consider taking a week-or-two to clear concretion from a cannon ball “not that long a process.” But clearing the concretion is a relatively quick process compared with cleaning the artifact of the element that started the concretion in the first place.
“Once we take the concretion out, the cannon ball that it was inside is still laden with all of the salt from the sea water. The desalinization process, that’s the process that is such a long drawn-out process. For a cannon ball, that’s a 2-to-3 year process soaking in a bath to get all of the salt out of it.”
The conservation lab has some concreted items it plans on running through the 3-D technology. One concreted item that could come free before the 3-D is in place may be a manilla which was used as a type of currency in Africa into the 20th century. If it is in fact a manilla, it would be one more piece of evidence backing the wreck site as that of the Queen Anne’s Revenge as, prior to Blackbeard capturing the vessel, it was the Concorde, a French slaver with frequent excursions to Africa. Still, it’s inside concretion and while the 2-D image is indefinite a 3-D image could provide something resembling conclusive evidence. But whether or not the possible manilla is still encased in its concretion when the 3-D software comes on-line this summer, there are plenty of other concretions raised from the Beaufort harbor wreck site that could benefit from the new technology.
“One of our more interesting pieces, is a small firearm, so it’s a personal arm, and it looks to still have all of the pieces in place. We have not found an object like that before. We’ve found gun parts but we’ve never found an articulated gun. That one will very specifically be important for us to capture in 3-D and that’s one that’s being planned on, the 3-D x-ray.”
Kim Kenyon is a conservator at the Queen Anne’s Revenge Conservation Lab in Greenville. I’m George Olsen.
(The Queen Anne's Revenge Conservation Lab in Greenville holds an open house Saturday, April 26 from 1100-1500.)
