The conservation and restoration of shipwreck artifacts is the process of caring for cultural heritage that has been part of a shipwreck. Oftentimes these cultural artifacts have been underwater for a great length of time. Without conservation, most artifacts would perish and important historical data would be lost.Hamilton, D. (1996). Introduction and Overview of Conservation in Archeology. In Basic methods of conserving underwater archaeological material culture (pp. 1–7). Washington, D.C.: U.S. Dept. of Defense, Legacy Resource Management Program. In archaeological terms, it is usually the responsibility of an archaeologist and conservator to ensure that material recovered from a shipwreck is properly cared for. The conservation phase is often time-consuming and expensive (sometimes costing more than the original excavation), which is one of the most important considerations when planning and implementing any action involving the recovery of artifacts from a shipwreck.
Background Underwater shipwreck sites are in either Freshwater or saltwater environments. It is important to distinguish that both environments react differently in relation to the shipwreck and the artifacts it contains. This can refer to the chemical reactions or corrosion that takes place, the rate of deterioration and decay, and the ultimate preservation of the shipwreck artifacts. When shipwrecks are in freshwater environments, they tend to be in a better state of preservation due to the lack of salinity in the water, and overall, have a lower degree of degradation compared to saltwater environments. However, in freshwater environments various bacteria can be a major threat to shipwrecks as it is known for causing the rotting and molding of wooden ships.
Artifacts recovered from a saltwater environment are saturated with salt that must be removed when the artifacts are recovered.Hamilton, D. (1996). Basic Conservation Procedure. In Basic Methods of Conserving Underwater Archaeological Material Culture (pp. 8–11). Washington, D.C.: U.S. Dept. of Defense, Legacy Resource Management Program. With saltwater environments, a phenomenon called concretion occurs. "Concretion occurs when a mixture of iron corrosion product, sand, and sea life forms a hard shell around corroding iron artifacts and can encompass other non-iron artifacts that may be nearby".Page, C. (2017, June 15). Conservation Highlights: Concretions. Conservation Highlights: Concretions | Queen Anne's Revenge Project (qaronline.org) Although they are often naturally preserved, they are also fragile and friable. Once these artifacts are exposed to air and light they will degrade rapidly,Martin, C. (n.d.). An Introduction to Marine Archaeology. Retrieved from: https://www.bbc.co.uk/history/ancient/archaeology/marine_01.shtml#four a concern which highlights the importance of timely conservation efforts. Material type is a key factor in determining proper conservation treatment methods. Organic material, such as wood, leather, and textiles, can deteriorate and crumble in a matter of hours if allowed to dry without appropriate treatment. Other materials, such as bone, glass, and pottery, if not conserved, will slowly devitrify and in extreme cases will degenerate into a pile of slivers.
Agents of deterioration
Agents of deterioration consist of several types of forces that can drastically affect and cause artifacts to deteriorate. To protect an artifact from deterioration and destruction, conservators must use conservation and preservation methods to alleviate the potential risks to the artifact. The amount of damage caused by agents of deterioration can range from minor abrasion to the complete destruction of the artifact. There are ten agents of deterioration: physical force; thieves and vandals; fire; water; pests; pollutants; light, ultraviolet, infrared; incorrect temperature; incorrect relative humidity; and dissociation.
Physical force When it comes to the conservation, preservation and the restoration of shipwreck artifacts, physical force is a major concern. Agents of physical force are consistently present throughout the entire processes of conserving and preserving shipwreck artifacts. The retrieval of shipwreck artifacts from the seabed is an extremely intricate and fragile process. Artifacts are extremely delicate, and any slight motion or improper physical contact can cause irreputable damage. When the artifact is brought to the surface through the use of floatation devices, the placement and stabilization of the artifact is of the utmost importance. This is done to ensure the artifacts are well protected from any potential damage caused by the water and/or equipment. Additionally, the handling, movement and transportation of the artifact poses additional risks of contact through physical force. It is paramount that the conservator ensure precautions and appropriate measures are put in place to protect every artifact in each stage of movement and/or relocation.
Thieves and vandals As with all archaeological sites, thieves and vandals will always be a primary concern. As scuba diving grows in popularity and treasure hunters seek to make their fortunes, shipwrecks have become constant locations for looting and illegal salvaging. To combat the looting of shipwrecks the United States legislation passed the Abandoned Shipwrecks Act. The act's primary function is to safeguard shipwrecks, located in American waters, from unsanctioned salvaging, illicit looting, and total ruination. This is achieved by affording protection to the shipwreck through granting ownership of it to the state whose waters in which the wreck resides.
Fire Once shipwreck artifacts are brought to the surface, they become extremely vulnerable to fire. This is especially true for shipwreck artifacts that are composed of organic materials such as textiles, leather, and wood.
Water Although most shipwreck artifacts reside in water, water can be a significant problem that must be addressed. Water has a major impact on artifacts that have been submerged for prolonged periods of time. If organic materials, are removed too quickly and allowed to completely dry out without proper treatment, the artifacts will rapidly disintegrate. It is imperative that artifacts remain in water until the appropriate conservation and preservation techniques have been applied to them, ensuring they are protected, stabilized, and acclimated to their new environmental surroundings.
Pests Pests can be found both on dry land and underwater. It is no surprise that shipwrecks are extremely susceptible to both types, as they can cause extensive damage to the wrecks and their surrounding artifacts. An example of an underwater pest can be found in the shipwreck of the Titanic, where a newly identified microbe has been found within the "rusticles, the porous and delicate icicle-like structures that form on rusting iron ... actually feeding off the rusting metal". As these microbes continue eating the rusting metal, the shipwreck of the Titanic will soon be no more. Another underwater pest that can devour shipwrecks are wood eating shipworms. These small creatures can chew through wooden shipwrecks at a rapid pace, and if left unchecked can-do extensive damage to wrecks. Moreover, surface pests such as rodents, insects, and mold can cause even more devastation to shipwreck artifacts that have not been safely stored or tended to. Conservators must be aware of what pests a shipwreck and its artifacts could be introduced too and plan accordingly.
Pollutants Pollutants can refer to chemical reactions, air quality, and corrosion. As artifacts go through the various conservation techniques to protect and preserve them, conservators must be cognizant and monitor these artifacts consistently to ensure no further degradation takes place that could be due to unwanted chemical reactions or pollutants in the air. Conservators must also be highly aware of the chemical reactions that have already occurred to the artifacts being recovered such as concretion and metal oxidation.
Light When shipwreck artifacts are recovered it is important for conservators to evaluate how to create an appropriate environment with the correct light exposure. This is impeccably important for waterlogged wood and other organic materials as the direct presence of ultraviolet light/infrared radiation can cause degradation and eventual disintegration. The best practice is to keep shipwreck artifacts in a cooler storage environment with minimal access to light, which can cause unwanted heating and fluctuations in temperature, leading to extremely harmful results.
Temperature Like other historical and cultural artifacts, incorrect temperatures can have a devastating effect on shipwreck artifacts, particularly wood. Drastic temperature changes can cause irreversible damage to artifacts such as: warping, crumbling, or fragmenting. Higher temperatures, specifically, could result in humidity levels significantly rising which could cause further deterioration, infestations of insects, molds, rot, and bacteria.
Relative humidity As discussed previously, high relative humidity may result in mold, infestations, rot and even undesirable chemical reactions or corrosion, depending on environmental conditions. Incorrect relative humidity can cause biological deterioration of shipwreck artifacts, resulting in cracking, crumbling, or complete disintegration of the artifacts, especially organic materials. Even metal artifacts need to be protected from the corroding effects caused by a higher relative humidity.
Dissociation It is important to ensure that records for shipwreck artifacts are accurate and detailed. Without accurate documentation an artifact could be mislabeled and associated with an incorrect wreck site. This is vital for shipwreck discoveries as they can become points of contention in international legal battles over ownership. Furthermore, shipwreck artifacts removed without care and at random are subjected to become dissociated and lose their provenience. This dissociation causes a great loss of information about the artifact and its relevance to the shipwreck.
Basic conservation of shipwreck artifacts by material type
Bone and ivory Approximately 70% of bone and ivory is made up of an inorganic lattice composed of calcium phosphate and various carbonates and fluorides, and at least 30% is ossein, which is organic. It is difficult to distinguish them unless examined microscopically.Hamilton, D. (1996). Bone, Ivory, Teeth and Antler. In Basic Methods of Conserving Underwater Archaeological Material Culture (pp. 16–18). Washington, D.C.: U.S. Dept. of Defense, Legacy Resource Management Program. Both bone and ivory are easily warped by heat and moisture, and deteriorate by prolonged exposure to water.
Cleaning
Removal of soluble salts Bone and ivory being at a saltwater environment will absorb soluble salts and crystallizes when removed from water as the object drys. The salt crystallization will make the surface flake and can destroy the object. In some cases when bone and ivory suffer ossein loss due to hydrolysis, it leaves the calcareous substance; the calcareous substance can cause the materials to fossilise and once organic content is lost resulting in crystallisation, quartz can be formed.Conservation of Underwater Cultural Heritage. (n.d.). Retrieved from: http://www.mecd.gob.es/cultura-mecd/en/dms/mecd/cultura-mecd/areas-cultura/patrimonio/mc/libroverde/capitulos/capitulo6EN.pdf The soluble salt must be removed to preserve and stabilize the object when removed from the marine environment. Artifacts of these types of material are recommended to remove all the soluble salts with the use of water.
Removal of stains