Expeditions to the Monitor have yielded an amazing variety of artifacts. In 2002 alone, The Mariners’ Museum processed more than 800 artifacts to be conserved and prepared for exhibition at The Monitor Center.
In the Batten Conservation Laboratory Complex, visitors can take a close-up look at how the ironclad’s turret, steam engine, condenser, Dahlgren shell guns, auxiliary machinery, and other components are being preserved for future generations. Expeditions to the Monitor have yielded an amazing variety of artifacts: huge iron components, delicate glass bottles, lumps of coal, wood paneling, a leather book cover, walnut shells, and corn kernels. Thousands of artifacts and components arrived at The Mariners’ Museum to be conserved and prepared for exhibition at The Monitor Center. Each artifact presents a different challenge to conservators as they seek to stabilize the damage done by nearly 140 years of immersion in saltwater. Once-mighty iron components such as the engine, turret, and propeller have been rendered so fragile that they will disintegrate without years of painstaking treatment. Iron and brass artifacts and components are treated with electrolytic reduction, desalinated, rinsed, dehydrated, and protected with various coatings. This process can take years or decades to complete. In contrast, delicate glass fragments can be more easily cleaned and readied for exhibition in just a few weeks.
Fragile as iron: A conservation challenge.
Courtesy of the Daily Press
Conserving the iron artifacts recovered from the Monitor is a race against time. The ship’s fragile, salt-contaminated iron can break apart if exposed to the air for long periods of time. After recovery, the artifacts are kept wet and quickly transported to The Mariners’ Museum, where they begin intensive treatment to counteract the effects of being submerged in seawater for nearly 140 years.
The Corrosion Process
In a dynamic environment such as the sea bottom, iron corrodes rapidly. The iron absorbs salts, which could form crystals within the material if it were allowed to dry. This reaction can cause the material to break apart, much like frost-heaving in frozen soil. Conserving iron pieces recovered from the sea involves reduction of the object to arrest corrosion, stabilization of the material, and removal of the salt. The length of time for the process depends on the rate at which salt can be removed from the corroded iron. Large items with thicker corrosion layers, such as the engine or propeller, require more time than do smaller ones. Artifacts from the Monitor are kept wet to prevent drying and the formation of salt crystals. Equally important is retaining the marine encrustations that cover the artifacts because they protect the fragile surfaces from physical damage and atmospheric levels of oxygen that can speed the corrosion process. The fragile, salt-contaminated iron artifacts recovered from the Monitor present great challenges to conservators. Almost 200 tons of iron items have been raised from the wreck and will require decades of treatment before the deteriorated metal is stable. Each artifact will be placed on display in the Ironclad Revolution gallery upon completion of the conservation process.
Layers of Decay
Submerged iron oxidizes into various corrosion compounds that form in unstable layers and will disintegrate over time. Iron and other metals become covered with surface encrustations, called concretion. Concretion is a combination of sand, sediment, marine life, and iron oxides (rust) that bonds to the surface of an artifact. Iron and other material types also absorb chlorides (salt) from sea water, which destabilize the iron and accelerate corrosion. They also crystallize when dry and can cause structural failure of an artifact.