Conservation

For more than a century, the Monitor’s resting place in the “Graveyard of the Atlantic” remained a mystery despite numerous searches. Discovered in 1973, the wrecksite became the first National Marine Sanctuary in 1975 under the auspices of NOAA. Today, conserving the recovered iron artifacts is a race against time. Each item presents a different challenge to conservators as they seek to reverse the damage done by nearly 140 years of immersion in saltwater.

 

A Race To Save History

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. 

 

 

The gun turret of the USS Monitor

The gun turret of the USS Monitor

Monitor’s rotating gun turret was an important technological advance in naval architecture and warfare. Its cylindrical frame was constructed of eight layers of 1″ thick wrought iron plates strong enough to withstand enemy fire. The turret rotated to aim the two XI” Dahlgren shell guns and then rotated away after firing to protect the sailors inside from return fire. When the Monitor sank, the vessel flipped over and the turret fell upside down onto the seabed. A number of important artifacts were excavated from this part of the ship, including the remains of two sailors. Visitors can see the turret in the Batten Conservation Laboratory Complex as it undergoes treatment in a large tank of water to prevent further corrosion.

The engine of the USS Monitor

The engine of the USS Monitor

Monitor’s coal-fired steam engine was another of engineer John Ericsson’s improved designs. He oriented the engine so that the piston oscillated horizontally instead of vertically, greatly reducing the height of the engine compartment, allowing it to stay below the waterline. The components of the engine are constructed of various material types: iron, brass, nickel alloys, glass, rubber, grease, and coatings. Conservators will disassemble the engine so that each component can be conserved without negative effects on other components. Upon conclusion of the treatment, the engine will be reassembled and placed on display in the Large Artifact Gallery of Ironclad Revolution.

The condenser is part of the Monitor’s steam engine propulsion assembly. After steam moved the engine piston that turned the propeller, it passed through the condenser where it expanded into cooler, lower pressure gas that was discharged from the engine room. The condenser is another example of a large, complex artifact with many composite parts.

The Dahlgren shell gun of the USS Monitor

The Dahlgren Shell Gun of the USS Monitor

The Monitor was armed with two XI-Inch Dahlgren shell guns that were located inside the revolving gun turret. The cast iron guns are over thirteen feet long with a bore diameter of eleven inches. Each gun weighs approximately eight tons. Rear Admiral John A. Dahlgren designed the guns, numbers 27 and 28, which were manufactured at Robert P. Parrott’s West Point Foundry in Cold Springs, NY in 1859. After the battle with the C.S.S. Virginia, one was engraved “Monitor & Merrimac- Worden” to commemorate the battle and captain of the Monitor. The other gun was engraved “Monitor & Merrimac- Ericsson” to honor the man who designed the revolutionary warship. Visitors can see these massive guns undergoing electrolytic reduction and desalination in the Batten Conservation Laboratory Complex.

Monitor’s Dahlgren guns rested on specially designed gun carriages. Each carriage rolled back and forth on massive iron rails on the floor of the turret. A large brass wheel on the side of each carriage tightened or loosened a braking assembly to allow safe operation of the guns. During initial test firing, a sailor accidentally loosened rather than tightened both gun carriage brake assemblies. When the guns fired, both carriages recoiled and slammed into the rear wall of the turret. When archaeologists excavated the gun turret, both carriages were resting on top of the cannons because the turret flipped upside down. This fact, coupled with suction formed by layers of sediment and pressure from the sea, made both carriages difficult and dangerous to remove from the turret for treatment. Both carriages are now upright, partially disassembled, and desalinating in treatment tanks in the Batten Conservation Laboratory complex. Visitors can see these 3,200 pound carriages from a special viewing platform.

The Worthington simplex pumps, or “donkey pumps”, were hardworking general purpose pumps. They were used to pump feed water in and out of the boiler, as bilge pumps, and as essential firefighting pumps. Conservators at The Mariner’s Museum have already disassembled one of the pumps to facilitate easier treatment of the pump’s different component materials such as rubber, iron, brass, textiles and lead. The pump will be reassembled and placed on display when treatment is complete. The main iron cradle of each pump contains a casting that says “H. R. Worthington New York, Patented April 3, 1849.

The packing seal, or “stuffing box”, is an assembly of cast iron, wrought iron, and organic packing material that prevented water from entering the ship where the propeller shaft passed through the hull. The packing seal kept out leaks and still allowed the shaft to turn unimpeded. Sailors tightened two cast iron sleeves to compress a layer of plant fibers made waterproof with resins. At some point before excavation, the outer cast iron gland fractured, revealing an informative cross section the materials used in this part. The damage likely occurred during the wrecking process when a large section of the propeller shaft, near the packing seal, bent under the force of the sinking vessel.

The propeller of the USS <em>Monitor</em> in conservation

The propeller of the USS Monitor in conservation

Monitor’s four-blade, cast iron screw propeller is currently on display in the Large Artifact Gallery of the USS Monitor Center. The nine-foot diameter propeller was protected from enemy shot because it was located safely forward of the aft-most portion of the hull. The screw propeller was better protected than exposed paddlewheels on other ships at the time. This made it extremely difficult to crippleMonitor’s propulsion system.

The anchor of the USS Monitor

The anchor of the USS Monitor

Though it may not look like it, Monitor’s anchor is made of wrought iron. When wrought iron artifacts suchas this one corrode, the surfaces often look like decayed wood. The core of the anchor is still composed of solid, shiny iron despite its outward appearance. The anchor was recovered from the wreck site in the 1980′s and was the first large artifact treated.

Silverware from the USS Monitor

Silverware from the USS Monitor

During the excavation of Monitor’s revolving gun turret in 2002, archaeologists and conservators discovered twenty-four pieces of silverware. Some pieces of silverware were engraved with the names or initials of crewmembers or officers who served aboard the Monitor. A few pieces silverware carry the names of sailors who perished the night of the sinking, and these artifact offer a personal and emotional connection to the past.

The red lantern from the USS Monitor

The red lantern from the USS Monitor

On the night of December 31, 1862, while en route to the Carolinas, the Monitor sank in heavy seas off the coast of Cape Hatteras, North Carolina. Eye witnesses reported that at approximately 1:30 A.M., the red distress signal lantern burning atop the turret and the ship itself were no longer visible. Recovered in 1977, this lantern was discovered lying in the sand near USS Monitor’s turret. This lantern was the last visible sign of the Monitor before she sank and the very first artifact recovered from the wreck, signaling a rebirth of this mighty Civil War icon.

The reversing wheel of the USS Monitor

The reversing wheel of the USS Monitor

The engine’s reversing wheel is a large brass wheel with a single handle and six curved spokes. The engineer changed the orientation of the valves in the engine by turning the wheel, thus altering the direction of the steam hitting the pistons and changing the ship’s direction from forward to reverse. The recovery of the reversing wheel revealed a modification to Ericsson’s engine design; he had originally specified a hand crank.

The engine register is a brass gauge and was mounted to the ship’s engine. The engine register consists of a round metal container which houses six numbered brass wheels that would rotate as the propeller shaft turned. The numbered wheels reflected the number of revolutions made by the engine, (74,9088), during the vessel’s service. The function of this artifact was similar to an odometer in modern automobiles. The engine register faceplate reads “Monitor, Engine Register, 1862″ and was the first artifact recovered from the wreck with the vessel’s name on it. There is a small hole torn in the face of the register. This damage was likely caused by impact during the sinking.

The engine room clock from the USS Monitor

Engine room clock from the USS Monitor

Monitor’s engine room clock is built primarily of brass components. The clock also had a silvered face and glass plate, though the glass no longer remains intact. During treatment, a conservator discovered a maker’s mark on the surface of an interior component of the clock’s gear box. The mark, “V. GIROUD”, stands for Victor Giroud, a well-known clock maker in New York at the time of Monitor’s construction.

Rubber comb found in the USS Monitor's gun turret

Rubber comb found in the USS Monitor’s gun turret

Personal effects related to the men that served aboard Monitor offer a glimpse of life on an ironclad during the Civil War. Archaeologists excavated a rubber comb from sediment inside Monitor’s gun turret. The comb is a standard issue Navy comb and is made of black hard rubber with longer, wider teeth on one end and shorter thinner teeth on the other. The comb is inscribed with, “U.S. NAVY, IR. COMB Co. GOODYEARS PATENT MAY 6 1851″ and is in near perfect condition. It looks quite similar to plastic combs available in modern pharmacies.

Button found in the USS Monitor

Button found in the USS Monitor

Several naval jacket buttons have also been found during excavation. The large, round black buttons are made of India rubber. Each button has four small holes for attachment. The front has a circular edging around it with printing and three five-point stars above an anchor. The buttons are inscribed, “U.S.N. NOVELTY RUBBER Co / GOODYEAR’S PATENT / 1851 / NEW YORK”.

Only six ammunition cartridges have been recovered from the wreck. Each unfired, 0.56 rim-fire cartridge is composed of a lead bullet and copper alloy jacket. Some recovered cartridges are fragmentary while others are intact and likely still contain gunpowder and gun cotton.
A pencil from the turret is a great example of an everyday item used by crewmembers of the Monitor. This pencil is much like those we use today, with a graphite rod surrounded by two layers of wood. The wood separated from the graphite during burial, allowing us to see the graphite rod inside. Pencils are preferred writing instruments on naval ships because their markings don’t smudge if they get wet. Even after 140 years on the ocean floor, this pencil could still be used to write!
Archaeologists recovered a Wellington-style leather boot inside the turret. The boot may have belonged to an officer. The crew took off their shoes and heavy clothing as they prepared to leave the Monitor to board the lifeboats the night the ironclad sank. William Keeler wrote, “I divested myself of the greater portion of my clothing to afford me greater facilities for swimming in case of necessity…

 

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 theMonitor 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 

Layers of decay

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.

 

Large iron artifacts can require years of conservation. Multi-component objects such as Monitor’s steam engine and condenser must be disassembled to guarantee thorough treatment. Following documentation and disassembly, iron artifacts are conserved through a process called electrolytic reduction.

Electrolytic reduction is a process in which an artifact is placed in an alkaline solution of sodium hydroxide or sodium carbonate in deionized water. Metal electrodes are then suspended around the artifacts and a low-volt, low-amp current is passed through the object. The negative charge applied to the artifact forces negatively charge chloride (salt) ions from the artifact and into the storage solution. The positively charged electrodes help attract the negatively charge ions, increasing the rate at which they diffuse into solution. During this process, oxygen and hydrogen bubbles form at the artifact’s surface and help loosen and remove concretion from the artifact. The electrical current also consolidates and stabilizes weakened iron and reduces iron corrosion products to more stable forms. The chlorides are trapped in the electrolyte solution, which is changed when it becomes contaminated with chlorides. The process is complete when no more chlorides can be detected in the solution.

 

Electrolytic Reduction

 

 

FAQ

In order to complete the electrolytic reduction circuit in the conservation tank, there has to be a place for the electricity to go when it leaves the artifacts. Platinum coated wire, or electrodes, complete the circuit. Conservators also use stainless steel mesh in some tanks for the same purpose.
When the electric current flows out of the artifacts into the solution in the tank, it causes water molecules to break down into their component parts. This creates bubbles of hydrogen and oxygen.
It is estimated that it will take fifteen to twenty years to reduce the corrosion and to remove all the salt from the turret. Other objects, such as the engine, may also take more than a decade to desalinate.
Most materials made or refined by humans become altered by minerals and salt in the chemically and biologically active medium of sea water. If left untreated after recovery, these artifacts would rapidly corrode and disintegrate.
When the reduction and chloride removal phases of iron conservation have been completed, the artifacts are removed from the tanks. Their surfaces are stabilized with phosphates and tannates and conservators then apply special coatings to protect the artifacts from humidity, moisture, and other damaging substances.