SO482A.  Historic shipwrecks: Science, History, and Engineering

NAUTICAL ARCHAEOLOGY, ARTIFACT CONSERVATION,
AND SCIENTIFIC INVESTIGATIONS OF BONHOMME RICHARD


About the Presenter:

George Schwarz is an underwater archaeologist for the Naval History and Heritage Command’s Underwater Archaeology Branch (UAB). He earned an MA in Anthropology, with a specialization in nautical archaeology, from Texas A&M University. He is currently directing the archaeological investigation of the earliest-known example of a North American steamboat (Phoenix, 1819) as part of his doctoral research. As a member of the UAB, he handles naval ship and aircraft research, site survey and excavation, artifact conservation, and historic preservation policy for Navy’s submerged cultural resources. George also operates the UAB Archaeology and Conservation Laboratory and manages the Navy’s underwater archaeological collections.

 

 

Lesson Objectives:

Introduction to Nautical Archaeology

Principles and Practice

As a relatively new field of study, nautical archaeology has seen many changes in the past fifty years. Since its inception as a scientific field in the 1960s, it has been the submerged counterpart to terrestrial archaeology, applying the same scientific approach; the techniques for recovering the data being the greatest difference between them. This is not to say that the context of submerged sites is the same as land-based sites. Material recovered from terrestrial sites often represents long-term occupation and the artifacts survive in a complex pattern that requires great skill from the archaeologist to interpret. Often equally complicated to analyze, underwater sites usually represent a catastrophic event, such as a shipwreck, in which the events of a particular time are encapsulated in that one archaeological site. While in many cases artifacts from a terrestrial site are discovered in fragments and in different stratigraphic layers, objects recovered from marine sites are often found in tremendous states of preservation and integrity, and provide unique examples of tools, weapons, clothing, and technological designs of the past.

The chief objective of archaeological research is to recover information from historic and archaeological sites in order to reconstruct the past and preserve our knowledge of previous cultures. This is accomplished through scientific research, survey, excavation, documentation, analysis, and interpretation of sites. The field is aimed at conducting systematic research in order to generate new insights and ideas. Archaeology is not centered around the artifacts themselves, but the information gained from artifacts and the formation of archaeological sites which in turn help us solve problems and answer questions about past civilizations and events. Usually this is accomplished through the identification of patterns discovered through archaeological research.  The subsequent interpretation of these patterns is what tells us about past life styles and cultures that may no longer exist, allowing us to chronicle our existence as a species. 

Why can’t we gain the information that we need about the past from historical accounts? Why do we need archaeology to learn about historical periods? The study of historical periods, i.e. those that occur after the inception of widespread historical recordkeeping (typically after the 14th century in Europe), is immensely aided by archaeological research. Many events that were recorded in the past refer to monumental achievements, important people who accomplished incredible feats, high-profile battles, the building of city or town, or another event that someone deemed noteworthy. What about the life of the common subsistence farmer? Living aboard a vessel at sea for extended periods as a deck hand? Religious rituals that were passed down orally through tradition?  These and countless other examples of cultural or historic life ways are often overlooked in the historical record. No one thought to record the details of constructing a skiff, for example, that was used to transport men and equipment from one location to another in colonial North America because they were as common as small airplanes are today. These boats were generally built from accumulated knowledge obtained through the family or apprenticeship for generations. For this reason, we do not know how those particular skiffs were built because the traditions eventually died out as more advanced technology became available. These are the kinds of things we can learn by combining historical research with archaeological research should we discover a sunken or buried skiff of this type. In fact, archaeology in general, but maritime archaeology in particular, is an interdisciplinary field which relies on history, ethnology, geology, oceanography, computer sciences, cultural and physical anthropology, linguistics, and a range of other disciplines.

Origins of Maritime Archaeology

For thousands of years, men have been recovering objects from sunken vessels. In the past, nets and grappling hooks were mostly used, with the aid of free divers in clear, warm, and relatively shallow waters. In the seventeenth century this was made more efficient through the use of the diving bell. Enclosed barrels were used in the eighteenth century, allowing for better positioning and more control underwater. In the nineteenth century hard hat diving was introduced, using surface-supplied gas. The most important early contribution to marine technology for underwater archaeology, however, was the aqualung (Figure 1), invented by Jacques-Yves Cousteau and Emil Gagnan in 1942. This self-contained breathing apparatus (scuba) permitted archaeologists to descend to the sites they were studying and recover material for preservation and interpretation. This technology was more affordable and easily accessible to the ordinary person compared with the mixed gases and hard hat gear previously employed. With these advances in diving technology, the discipline of maritime archaeology began to flourish.

Figure 1. The aqua-lung permitted archaeologists to dive on underwater sites. (http://vintagedivertreasures.com/AquaLung1958_8.jpg)

 

Initially, attempts to recover objects from shipwreck sites usually involved individuals motivated by profit, or souvenir hunters. In the era prior to WWII, even those individuals that operated under the guise of scholarship were mostly driven by antiquarian curiosity rather than the advancement of scientific knowledge.  More genuine attempts at underwater archaeological study began with the advent of the aqualung. One of the earliest serious attempts at the investigation of a shipwreck was performed by Jacque-Yves Cousteau himself (under the direction of archaeologist Fernand Benoit), during the excavation of two superimposed 1st- and 2nd-century Roman vessels at Grand Congloué near Marseilles in the 1950s. According to today’s standards, this wreck was very poorly documented and lacking in proper methodology (no site map was even produced of the wreck). Despite this, it was demonstrated that scientific divers could investigate an underwater site for the purposes of archaeological research using scuba.

Underwater archaeology as a discipline was developed in the early 1960s as Dr. George Bass began excavations of a Bronze Age (13th century B.C.) shipwreck at Cape Gelidonya, Turkey. This is considered by many to be the first attempt to conduct an underwater archaeological excavation to the same standards as a terrestrial site, and was a significant contribution to the study of Bronze Age trade in the eastern Mediterranean. Following this successful effort, Dr. Bass led a number of underwater excavations in Turkey, including 4th- and 7th-century wrecks off Yassi Ada (Figure 2). During the excavations of the Yassi Ada shipwrecks, underwater archaeological methods were further refined as new equipment became available and new ideas were generated for recording archaeological sites under water. Dr. Bass had led terrestrial excavations as a professor at University of Pennsylvania and applied the same principles to underwater work, recording features in great detail and fully documenting provenience (origin of discovery within an archaeological site) of artifacts recovered from the site. The standards that Dr. Bass initiated in the 1960s are what archaeologists still follow today. Throughout the 1970s, 80s, 90s, and into the 21st century a wide range of incredible technology has become available for conducting archaeological research under water and improving accuracy, but the archaeological and professional standards have remained the same.

Figure 2. Excavation of the 7th-century Yassi Ada shipwreck
(http://inadiscover.com/galleries/projects/Yassiada_-_ya7-657.jpg)

Standards and Ethics in Archaeology

What is the importance of recording these features in meticulous detail? Why can’t objects simply be raised from a submerged shipwreck and recorded after they are taken to a shore-based lab? As mentioned in the above section, gaining information from cultural resources is often dependent on deciphering patterns found in the archaeological remains of a site. Such patterns are recognized through the process of excavation and site recording. It is therefore critical that each object discovered during an excavation is recorded in situ (unmoved from its original place of disposition). As a site plan is created, each object is mapped in relation to other features and artifacts at the site in order to unveil patterns that may assist the archaeologists with analysis and interpretation of the culture that formed it. With this information, we can learn details about the site that we may otherwise not have known. At a shipwreck site, for example, it is often difficult to determine what part of the vessel you are looking at. In many cases, there are very few hull remains due to poor preservation of organics underwater. In order to determine where the galley is, for example, one must analyze the artifact concentrations. A scattering of bricks in one area may indicate the remains of a galley hearth. If there are ceramic and/or glass vessels in this area, this may further substantiate the possibility that food was served in this space. Have utensils, such as a spoons and knives, been found in the vicinity? By piecing together various clues, the spatial layout of the ship can be reconstructed even if there are no hull remains. In the investigation of ancient Roman vessels it is common that only a cargo of amphorae remain as evidence of a wrecked vessel (Figure 3). Nevertheless, through careful documentation, analysis, and interpretation of the surviving cargo material, a host of information about the type, size, and age of the ship can be uncovered. If amphorae are unceremoniously lifted from the wreck, there is no way to determine where they came from on the site, hindering the study of spatial analysis. 

Figure 3.  Amphorae cargo from a 1st-century Roman shipwreck (http://www.smh.com.au/ffximage/2006/11/14/shipwreck_wideweb__470x352,0.jpg)

 

For these reasons, there are archaeological standards and codes of conduct that most archaeologists adhere to when conducting fieldwork. A sound archaeological excavation should at the minimum include these components: careful and thorough project planning, in-depth archival research, site research and survey, documentation, excavation, site mapping, site preservation, artifact conservation, artifact analysis and interpretation, and publishing of results. In addition, it is unacceptable to disperse the collection. Artifacts are preserved for future interpretation and should be kept together for this intention, unless they are on a short-term loan to a museum or academic institution for educational or display purposes. A few of the published standards and guidelines are: the Secretary of the Interior Standards and Guidelines for Archaeological Documentation; the Society for Historical Archaeology Standards and Guidelines for the Curation of Archaeological Collections; and, the Register of Professional Archaeologists Standards of Research Performance. In addition, many states have their own archaeological guidelines for archaeologists wishing to conduct research on state property.

In addition to these standards, archaeologists operate under a code of ethics, variations of which have been published by many archaeological societies and professional organizations. A few include: American Anthropological Association’s Principles of Professional Responsibility; Register of Professional Archaeologists Code of Ethics; American Institute of Archaeology Code of Professional Standards; and, Society for American Archaeology Principles of Archaeological Ethics. In addition, there are codes of ethics for the conservation and curation of archaeological artifacts, such as The American Institute for Conservation of Historic and Artistic Works Code of Ethics.

Many underwater archaeologists worldwide generally agree on an additional code of ethics set forth in the UNESCO Convention on the Protection of the Underwater Cultural Heritage. The objectives of this convention aim to ensure and strengthen the protection of underwater cultural heritage. Parties that have agreed to the terms of the convention strive to preserve underwater cultural heritage for the benefit of humanity. Although the United States has not yet agreed to all terms of this convention, it supports the Annex to the convention entitled Rules Concerning Activities Directed at Underwater Cultural Heritage, which effectively serves as a code of ethics. Some of the general principles include: considering in situ preservation of underwater sites as the first option for preservation; prohibiting commercial exploitation of recovered artifacts; use of non-destructive techniques and survey methods; avoiding the unnecessary disturbance of human remains at an underwater site; proper recording of archaeological information; acquiring appropriate funding for research and conservation of archaeological material before project initiation; creating an environmental policy; planning a conservation program for recovered objects; and preparation of a final report.

Archaeologists generally agree that the information gained from an historic or archaeological site is part of society’s shared heritage and should therefore be made available to everyone. It is important, then, that the data should be disseminated to colleagues, reports should be generated and presentations given to members of the scientific community, and popular articles and documentaries created for the general public. Furthermore, material culture from archaeological sites should be made available for study as well as public viewing. This includes a collections management program which allows for shared access to these assets, whether this be at a state, national, or international museum, an academic institution, or a state or federal archaeology lab stored in environmentally-controlled facilities. It is the responsibility of the archaeologist to ensure that the knowledge gained from the research project is properly disseminated for everyone’s benefit.

Archaeological Investigations of Bonhomme Richard

Research and Survey Attempts

For the past five years, Naval History and Heritage Command and Ocean Technology Foundation, in collaboration with USNA, have been conducting research into the final disposition of Revolutionary warship Bonhomme Richard. To date there have been four survey projects in the North Sea covering over 500 square miles, with no sign of the remains of the ship or its cargo. The objective has been to locate Captain Jones’s sunken vessel for research and commemorative purposes. The US Navy’s interest in locating Bonhomme Richard revolves around the potential for conducting archaeological investigations of the wreck site, which could provide important information about the construction of 18th-century warships, life of period sailors aboard sea-going vessels, naval battle tactics, diversity of crewmembers, navigational equipment, rigging characteristics of Revolutionary warships, and many other topics regarding life at sea and the Battle of Flamborough Head.

Using information obtained from an array of historical documents referring to the Battle of Flamborough Head, drift models have been created which project possible trajectories of Bonhomme Richard before she sank. Using Geographic Information Systems and both hand-plotted and computer drift models, possible search areas were defined for each survey season. The projects conducted since 2006 have involved the use of a variety of  archaeological and oceanographic survey equipment, including magnetometer, sub-bottom profiler, multibeam echosounder, Remotely Operated Vehicles, Autonomous Underwater Vehicles, and even a nuclear submarine (Figure 4). The systematic approach taken by the project team has narrowed the search area during each year of survey, and dozens of shipwrecks have been discovered. There has not been, however, an underwater site that meets the criteria for Bonhomme Richard to date.

What identifying features are archaeologists looking for? Will Bonhomme Richard be an intact vessel lying on the sea floor? Probably not. There are many factors that determine what archaeologists call the site formation process. Due to the mobile sea floor, North Sea currents, oxygen-rich environment, and generations of trawling in the North Sea, it is unlikely that much of the hull will remain. It is expected that any surviving hull remains will be pinned beneath the 200 tons of pig iron that was used to ballast the ship. If the lowest portion of the hull, where this ballast was positioned, managed to get buried in the silty bottom, there may be good preservation of hull timbers. The upper portion of the hull, however, will have broken apart and degraded long ago. What is likely to remain is the relatively stable iron ballast and the twenty-eight twelve-pounders that stayed with the vessel as she sank. This large mass of iron is one of the identifying features that archaeologists hope to detect with remote sensing techniques.

Figure 4. USN nuclear research submarine NR-1 preparing for the 2008 survey for Bonhomme Richard.  (Image:  G. Schwarz)

 

Identification

When the mound of cannon and pig ballast are detected by the remote sensing operations, a likely candidate for Bonhomme Richard will have been located.  What other evidence do we need to positively identify Bonhomme Richard? The detection of a significant magnetic anomaly over a wreck site is obviously not enough to claim the site represents the remains of the ship in question. The first thing to consider is the condition of the cannon. Iron that has been submerged in sea water for extended periods of time undergo chemical alterations as the chloride ions are attracted to the ferrous material. Relocation to an unstable environment causes the iron to slowly revert back to its natural ore. In the process, sea salts, marine life, and other materials form a concretion around the iron, resulting in an amorphous shape that often disguises the object. Archaeologists or remotely operated vehicles with video cameras would need to descend to the site to verify what kind of material was detected by the magnetometer.

Other features that would help identify the wreck as Bonhomme Richard might include iron reinforcements, called knees, that were known to have been used in the construction of the ship (Figure 5). Also, if portions of the hull did survive, robust timbers (Figure 6) would be expected since this was an 900-ton sturdily-built vessel modified by Jones to carry a large complement of cannon. Burnt hull remains might also be discovered, given the history of the battle and the immense damage sustained by Bonhomme Richard.

Figure 5. Iron knees similar to those used on the Bonhomme Richard. (Image:  Jean Boudriot)

Figure 6. Degraded timbers from a 13th-century shipwreck in Japan, previously buried in a sandy bottom.

 (Image:  G. Schwarz)

 

In addition to the cannon and ballast, a range of artifacts might also be discovered buried with the lowest portions of the hull which could provide clues. Materials might be comprised of iron, copper, wood, leather, textiles, lead, glass, ceramics, or a combination of material (Figure 7). These objects, especially the ceramic vessels, could be dated to a particular period using known examples, helping to identify the remains of the shipwreck as a Revolutionary War vessel. Wood samples could be taken to identify the species, and dendrochronological studies could be conducted to date the timbers. Officers' buckles might help confirm whether it was a U.S. Continental Navy vessel or another war ship from that era. Recovered weapons, such as swords and pistols, might aid in the investigation. In addition to helping to identify the wreck, the documentation and study of these recovered objects would contribute to our knowledge of maritime culture during the Revolutionary War.

Figure 7. Cannon cascabel and leather binding from an early 19th-century shipwreck undergoing conservation.
 (Image:  G. Schwarz)

 

Excavation vs. In Situ Preservation

So what happens to Bonhomme Richard when her remains are discovered? Do we acknowledge the fact that we finally know where her final resting place is, and leave the wreck site undisturbed for future generations? Do scientists fully excavate the wreck and bring the entire ship to the surface for long-term preservation? Or do we take an approach somewhere in the middle? As has been seen throughout the history of underwater archaeology, time can have a detrimental effect on many underwater sites. While many sites reach a state of equilibrium and are well-preserved in an underwater environment, others continue to deteriorate until nothing remains.

The location of the wreck has a major impact on the preservation of the site. Consider the following scenarios. If a rare 17th-century Spanish ship is found wrecked in shallow, warm, clear waters and its disposition is well-known, the chances are high that it will be stripped of all archaeological value by treasure hunters with little regard for provenience. When a site such as this is discovered, most underwater cultural resource managers would consider this an endangered resource and high priority for preservation. Not only is looting a high probability, despite laws protecting these resources, the warm water hosts wood-boring organisms that accelerate deterioration of organic material. If funding is available for recovery and conservation, this type of site would be a good candidate for full excavation and recovery of the hull remains in addition to discovered artifacts. More knowledge and public benefit could be obtained if the hull and associated artifacts were conserved, studied, and put on public display rather than left to teredo worms (Teredo navalis) and treasure hunters who might reduce the remains of the shipwreck to an unrecognizable mound on the seafloor.

Now, let's examine the other side of the spectrum. A rare WWII aircraft is discovered in Lake Michigan in a good state of preservation at 350 feet in dark, cold, freshwater (Figure 8). After conducting extensive archival research, it is determined that the events surrounding the sinking of this aircraft indicate that the site could also be a war grave. Aircraft enthusiasts may want to raise such a rare craft and put it on display in a local aviation museum since it is a unique specimen and in good condition. Is this a wise objective? Some may argue there is more to gain from raising the plane and permitting the public to view it than leaving it on the lake bed to deteriorate. This line of reasoning, however, does not consider the long-term preservation of the resource. There are, in fact, many reasons why state and federal archaeologists and historic preservationists would prefer to preserve the cultural resource in situ. First, little is known of the long-term corrosive properties of aluminum and its alloys. Consequently, conservation of these materials are still in its infancy. There are many cases in the past in which such craft were recovered from lakes, rivers, and oceans, and were left to deteriorate because the salvors did not have a sound conservation plan or funds to preserve the aircraft. Second, recent studies in in situ preservation have shown that many such aircraft have reached a state of equilibrium in which the rate of deterioration has slowed to such as point as to be almost non-existent. Therefore, in such instances it may be better to create a management plan for the resource, monitoring its condition and preventing unauthorized disturbance so that future generations can enjoy it as a submerged archaeological resource in an underwater preserve until more is known about the conservation and long-term preservation of complex alloys. Third, as a war grave, it signifies the final resting place of the aviator who went down with the plane while doing his duty for his country. As such,  the site may be best left undisturbed and treated with respect unless imminently threatened.

Figure 8.  Assessment of a well-preserved sunken WWII aircraft site.

 (Image:  Naval History and Heritage Command)

So, where does Bonhomme Richard fit in to this spectrum? Its location on the bottom of the North Sea is the first consideration. In what shape is the ship likely to be found? As we already discussed, the preservation of the hull timbers will be minimal. So, we are possibly looking at the bottom-most portion of the hull pinned under 200 tons of ballast, perhaps buried in the silty sea floor. We also know that the iron cannon will have formed thick encrustations rife with sea growth. Artifacts that have not been destroyed by the generations of trawling in the North Sea will likely be embedded in similar encrustations, in varying degrees of preservation. Many of these artifacts will, perhaps, be buried with any hull remains. From this information we can clearly see that this is not a case similar to the sunken aircraft in Lake Michigan. Most wooden shipwrecks rarely reach a state of equilibrium unless they become buried in fine sediment which provides an anaerobic environment suitable for preservation of organic material. As Bonhomme Richard had sustained incredible damage during the battle, any structural integrity retained by the hull and upper works was quickly compromised by the harsh currents, sea organisms, and later trawling in the North Sea. What is expected is a non-descript archaeological site with clusters of concreted artifacts (mostly cannon) and buried hull remains. In this case, in situ preservation  may not be a logical choice for the management of this significant warship from the early years of the US Continental Navy.

It must also be considered that the Bonhomme Richard site is a war grave. Any human remains discovered at the site must be treated with respect, and will be a factor in the decision to disturb the site. As long as any preserved remains are properly cared for, however, archaeological research should not be a hindrance to the final resting place of the sailors who perished as the ship sank. Human remains can either be documented and left buried at the site, or properly recovered, identified, and preserved, as in the case of the seven crewmembers from the Civil War submarine HL Hunley. In this case, the crewmembers were subsequently given a proper burial and are memorialized as Civil War heroes in Charleston, South Carolina.

Does a full excavation of the Bonhomme Richard site ensue? Assuming appropriate funding for such a project is available, this could be a viable option. There are many considerations, however, when planning a complete recovery. Funding must not only be guaranteed for the archaeological excavation, but also for the conservation of the recovered hull timbers, cannon, and myriad other artifacts that may result from this effort. Conservation is a long-term process that can often cost many times what the actual field excavation costs, especially when preserving hull remains. The hull of the 17th-century French frigate La Belle, discovered in Matagorda Bay, Texas, in 1995, is still undergoing conservation at Texas A&M University and has so far cost over five million dollars (Figure 9). In addition, after the hull timbers are conserved, there must be a place designated for its long-term curation and perhaps public display.

Figure 9. La Belle undergoing conservation in a large custom built vat.

 

Is this an appropriate use of public funds? Possibly, but if only a small portion of the hull of Bonhomme Richard exists, it may not warrant this type of recovery. A better option may be to excavate the site and fully document the hull remains in situ, carefully mapping each artifact and creating a comprehensive site plan (Figure 10). Recovery of cannon and other artifacts could occur up to the point of available conservation and curation funds. Samples of the hull could be taken for conservation and study, leaving the majority of the hull timbers buried in the North Sea for long-term preservation. With this data, archaeologists could obtain a wealth of knowledge without having to expend vast resources to conserve the hull and potentially thousands of artifacts. This approach would also allow for future recovery of hull remains and additional artifacts should funds become available to future researchers. 

Figure 10. Navy archaeologists map an early 19th-century shipwreck.

(Image:  Naval History and Heritage Command)

Conservation of Marine Artifacts from Bonhomme Richard

Conservation Principles

Artifacts that are recovered from Bonhomme Richard would have to undergo extensive conservation. Objects recovered from sea water are often well-preserved but require immediate treatment to prevent rapid deterioration, which ruins their potential as diagnostic or display specimens.

As is often the case with archaeological metals, for example, ferrous materials from antiquity tend to revert back to their natural ore. When dried, leather and organics shrink and become brittle, thereby distorting their original form and often deteriorating beyond recognition. Bone, ivory, and glass, if not properly conserved, will devitrify and become malformed. Thus, conservation is the foremost concern when undertaking recovery of archaeological material from underwater sites. Even after they are stabilized, objects excavated from underwater sites require periodic monitoring and evaluation, as they are susceptible to fluctuations in their immediate environment.

The primary objective in treating artifacts recovered from saltwater environments is to remove the imbedded salts, which accelerate deterioration. Regardless of the material, if left to dry the salts will crystallize and compromise the integrity of the material, often forming cracks and causing flaking. The first step, then, is to keep the object submerged and reduce the chlorides in storage solution. This is achieved through different methods, depending on availability of equipment and the type of material being treated.

Metals

Metal objects, as described above, would be encrusted and likely hard to distinguish until conservation began. In addition to the cannon and iron ballast, brass pins, iron fasteners, iron anchors, iron and lead shot, pewter plates, and copper alloy buttons and belt buckles are all likely to have survived from Bonhomme Richard. As the objects are usually encrusted with chlorides, sand, and bits of sea life, this outer layer of concretion must be mechanically removed with metal picks or pneumatic chisels. The exposed metals are then placed in baths of tap water, which has a lower chloride count than the seawater from which they were recovered. The amount of chlorides in solution are periodically checked, and the baths changed as the chlorides levels off. Eventually the objects will be placed in deionized water, and the same routine will take place as the chlorides are leached out. Generally, the metal objects will also be placed in a dilute solution of sodium carbonate or sodium hydroxide to further reduce the chlorides and prevent rusting during treatment. This can be a long process, however, and other treatments have been developed to speed the desalination. Electrolytic reduction, or ER, is a common treatment for metals—typically iron objects—which involves submerging the artifact into an electrolyte such as sodium hydroxide, and applying a low voltage direct current to the object. This process removes chlorides much more rapidly through the evolution of hydrogen.

After the process of chloride removal, iron artifacts are painted with several dilute solutions of tannic acid, which penetrates the surface and acts as a corrosion-resistant barrier. Following this treatment,  the objects are submerged in a vat of boiling microcrystalline wax to provide an additional layer of protection from the fluctuations in temperature and relative humidity, which can cause further deterioration. Though this is a common treatment for iron objects, the proper treatment of individual metals varies depending on the chemical properties of the particular material and its state of preservation.

Organics

Although organic objects such as leather, wood, textile, and rope, require specialized treatment, chloride removal is the first priority. Like the metal objects, organic material must also be kept wet during this process. Chloride removal is achieved in a similar manner, with baths of tap and deionized water. Because cellular structure is often times severely compromised, however, the conservation treatment is generally aimed at supplanting the water in the cell walls with a bulking agent. In this way, when the artifacts are finally air-dried after conservation, they do not collapse due to lack of structural integrity. Treatment with polyethyleneglycol (PEG), silicone oil, natural rosin, sucrose, or another bulking agent is commonly performed to retain the original shape and condition of the object, as organics have a tendency to shrink and warp when dried.

Ceramics, Glass, and Bone

It is possible that ceramic dishware, glass vessels, and animal or human bone have survived at the Bonhomme Richard site. These objects require removal of soluble and insoluble salts in order to prevent surface cracking or flaking. Insoluble salts can often be removed mechanically while still wet by using a scalpel or dental tool. For pottery, chemical treatment is sometimes required for stain removal. Once this is accomplished, pottery is consolidated by immersion in a dilute adhesive as a protective barrier. Because archaeological glass is susceptible to weeping, it is usually soaked in distilled water, dried in baths of alcohol, and coated with an organic lacquer to impede disintegration (Figure 11).

Figure 11. Rigging element from CSS Alabama undergoing treatment.

(Image:  G. Schwarz)

Archaeological bone recovered from underwater sites has the tendency to be spongy and full of soluble salts. These salts are generally removed with repeated water baths, then the bone is dried in a series of alcohol baths. Subsequently, the bone can be consolidated with an appropriate dilute adhesive.

Concluding Remarks

Whether the decision is made to fully excavate or partially excavate and record the site of Bonhomme Richard upon discovery, accepted archaeological standards and ethics need to be adhered to. As with all responsible archaeological projects, adequate funding should be secured before the project begins, and must consider not only the excavation, but the long-term preservation of the material culture and the analysis, interpretation, and publishing of collected data. Conservation of recovered material should be fully addressed, as well as the long-term curation of the artifact collection. A wealth of knowledge can be learned by discovering and subsequently investigating the remains of Bonhomme Richard, but proper scientific methodology, preservation, and dissemination of knowledge is essential to the world-wide benefit of this endeavor. This can be accomplished by careful planning, use of proven field methods, and a strong desire to share the history and archaeology of Bonhomme Richard with the rest of the scientific community, students, current Navy seamen, and the general public.

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References:

Bass, G., editor. 1972.A History of Seafaring Based on Underwater Archaeology. Walker and Co., New York.

Boudriot, J. 1988.  Bonhomme Richard, 1779.  Boudriot, France.

Green, J. 2004. Maritime Archaeology: A Technical Handbook, second edition. Elsevier Academic Press, London, UK.

Hamilton, D. 1996. Basic Methods of Conserving Underwater Cultural Material. US Department of Defense Legacy Resource Management Program, Washington, DC.

Muckelroy, K. 1978. Maritime Archaeology. Cambridge University Press, London, UK.

Ruppé, C. and J. Barstad, editors. 2002. International Handbook of Underwater Archaeology. Kluwer Academic/Plenum Publishers, New York.

Steffy, J.R. 1994. Wooden Ship Building and the Interpretation of Shipwrecks. Texas A&M University Press/Chatham Publishing, College Station, TX/London, UK.


Last revision 3/5/2010