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In March 1997, archaeologists made an exciting announcement in Raleigh: divers had discovered a wreck off Beaufort Inlet they believed to be the Queen Anne's Revenge, the flagship of the famous pirate Edward Teach, better known as Blackbeard. The Queen Anne's Revenge sank in approximately this location in June 1718. A diving expedition in October 1997 provided additional evidence strongly suggesting that the wreck is, indeed, the Queen Anne's Revenge.
Since the summer of 1998, some of the more durable artifacts from the ship have been touring eastern North Carolina in a traveling exhibit assembled by the NC Divison of Archives and History. However, many interesting artifacts haven't been seen yet, because they are still being processed to eliminate salt water and stabilize them for study.
In September 1998, divers resumed their work at the wreck site. In addition to raising a third cannon from the wreck, they have discovered medical and scienctific instruments which apparently belonged to a doctor Blackbeard kidnapped from Charleston to minister to his crew. And they found gold: a few small flecks, tiny pieces of Blackbeard's treasure. (The expedition's leaders believe Blackbeard had plenty of time to remove valuables form the ship, so they don't expect any major gold finds.)
Since we do science here, rather than history, we're interested in the scientific aspects of this discovery. In particular, we'd like to know:
The first question is the easier one to answer. There are a lot of lines of evidence leading to the conviction that the wreck is the Queen Anne's Revenge, but these three convince most scientists:
The care and preservation of artifacts is important and difficult, even for ordinary archaeology on land; it's much harder for underwater archaeologists. The things archaeologists remove from a site are irreplaceable, and so preserving them is really the most important aspect of archaeology.
There's an important distinction between cleaning and preserving an artifact. The items brought up from the Queen Anne's Revenge (we're going to assume that's what it is) must all be cleaned, at least to remove the mud and the barnacles and other marine animals that may be living on them. But archeologists do as little cleaning as possible, because cleaning means scraping the surface and possibly changing r damaging the artifact. Once the obviously necessary cleaning is done, the work of preservation can begin.
Water, by itself, is damaging to many materials, but the real villain in a maritime shipwreck is the salt in the seawater. Sea salt doesn't exist as little crystals of table salt floating around in the water: the salt is dissolved into its individual atoms. These atoms, called ions, are electrically charged. The most damaging ions are those of atoms such as chlorine, which carry a negative charge.
Everything on the Queen Anne's Revenge is saturated with salt. Nothing can keep salt out for 280 years; even heavy cannonballs are permeated with it.
If an artifact is removed from seawater and allowed to dry out, the salt will crystallize inside the artifact. This is frequently disastrous, because the salt crystals are likely to break the artifact, causing it to shatter or crumble. Therefore, artifacts pulled from the sea must be quickly immersed in tanks of water.
Now the problem is to get the salt out of the artifact. Very basic chemistry is the key to this process. If the item is kept bathed in pure, fresh water, the salt inside will not be in equilibrium with the saltless water outside. So chlorine ions will slowly drift out of the object until their concentration outside is the same as the concentration inside. Then the water is poured away and replaced with pure, fresh water again. This is a tedious process, and it can't really be hurried.
Eventually, no more salt comes out of the artifact. But, depending on the material involved, there may still be some inside, trapped or bound in the material. To get this stubborn salt out, a process called electrolysis is often used. The object is connected to a negative charge, and a positive electrode is placed in the water. Since opposite charges attract, the negative chlorine ions will migrate outside, seeking the positive electrode.
Of course, getting the salt out isn't the only problem preservationists have. For example, many of the artifacts are made of iron. As everyone know, water causes iron to rust, that is, to form compounds of iron and oxygen, iron oxides. There's no way to turn rust back into pure iron, but chemical treatments can turn the various iron oxides into mostly hematite (Fe2O3), a more stable material which will help keep the artifact from crumbling in the air.
Other materials also pose special problems, for which preservations have developed a large stock of special treatment techniques. Furthermore, many artifacts combine several materials, such as brass and iron, and these objects may require several of these techniques before they are ready to face the atmosphere.
All in all, it's not so surprising that we'll all have to wait a few years to see most of the wonderful things recovered from the Queen Anne's Revenge. But the wait should be well worth it.
Internet Sources
Posted December 1, 1997. New links added January 13, 1998, and June 8, 1998. Updated and links checked October 12, 1998. Link added October 14, 1998. Revised December 11, 1998. Links checked and ECU link added June 1, 1999. Features remain online as long as they remain current; they may be updated if new information becomes available.
Copyright © 1999, Center for Mathematics and Science Education. Teachers have permission to duplicate this page for use in teaching their own classes. All other rights reserved. You are welcome to link to this page, but do not copy its contents.
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