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A team of scientists and conservators, including Desmond Cook, professor of physics at Old Dominion University, has high hopes for a new process
developed to protect artifacts from the Civil War ironclad USS Monitor.

Experiments are being conducted utilizing "critical fluid" processes in pressurized chambers. Water and other fluids under high pressure, and sometimes high heat, are used to remove harmful chemicals from samples of iron and wood. Fluids in a chamber isolate or break down contaminants under conditions similar to those found in a typical kitchen pressure cooker.

"Critical fluid technology will revolutionize artifact conservation and then be accepted for many more corrosion-related issues," Cook predicted. "Its future is as exciting as it can get if we can get the funding we need to develop this method."

Cook, who for two decades has been a rust-buster working on troublesome rust problems affecting bridges and other steel structures, was the right
man in the right place when The Mariners' Museum in Newport News was chosen to be the home of the Monitor conservation effort.

"I feel fortunate that these artifacts came right here into my backyard," he said, referring to the more than 1,000 pieces of the ironclad vessel and shipboard articles that have been recovered so far from the Monitor wreck site 16 miles off Cape Hatteras, N.C. Those pieces include the well-known
turret, two massive guns and the vessel's steam engine.

Cook's role in the conservation of the Monitor is noted in a feature article, "Up from the Deep," in the October issue of Materials Performance magazine.

"Through his work on the Monitor and other historical conservation projects, Cook hopes to develop new conservation techniques that will in turn lead to new information for the corrosion community" to use in protecting structures such as bridges, oil rigs and pipelines, the article states.

Little scientific research has been done on corrosion of wrought iron and cast iron, both of which are prominent in the makeup of the Monitor artifacts. With the Monitor project being hailed as the most important salvage effort ever of a sunken battleship, scientists and conservators are under a lot of pressure to design and implement a fail-safe conservation strategy, Cook said.

"The history of this sort of work is littered with mistakes," he explained, citing instances in which marine artifacts deteriorated despite conservation treatments.

Conventional conservation strategies for shipwreck articles involve alkaline baths-often juiced with electrical current-that last for years, perhaps a decade or more.

"The problem with this technique is that when chloride (salt) extraction rates are low, the chloride is assumed to be all removed," Cook said. "But this is not true. Residual chloride remains. So after many years of electrolytic treatment, you still end up with enough chlorides to cause failure later."

As it happened, the Monitor recovery effort over the last decade has coincided with a similar effort for another Civil War vessel, the Confederate submarine H.L. Hunley. It is also constructed of wrought and cast iron and presents similar conservation challenges. The 40-foot Hunley, which sank at the entrance of the Charleston, S.C., harbor in 1864 and was raised in 2000, is at the Warren Lasch Conservation Center in Charleston.

Scientists from Clemson University took on the challenge of helping to conserve the Hunley and it was their innovation to employ critical fluid technology. Cook and colleagues at Clemson have now combined their efforts in order to assist both conservation projects.

"My work with the Hunley project involves working with researchers fromClemson to develop and evaluate the critical fluid extraction process and facility," Cook said. "This work is done in Charleston, but I do all the materials analysis, pre- and post-treatment, at ODU. The analytical techniques I use have been developed from my work involving steel bridge corrosion evaluation due to marine and de-icing salt exposure."

Cook said his goal is eventually to have critical fluid technology
facilities at ODU's Applied Research Center in Newport News, allowing
extraction experiments as well as analysis with sophisticated spectroscopy,
X-ray diffraction and electron microprobes to be done under one roof.

Critical fluid technology involves different types of processes.
Supercritical fluid extraction is a three-decade-old process that at times
has put liquefied carbon dioxide to work to separate caffeine from coffee
and cholesterol from eggs. When waterlogged wood is the target,
supercritical reactions can remove water without causing the cracking and
other damage that comes from air-drying wood, and other treatments.

"Supercritical" means that a substance such as carbon dioxide has been
heated and pressurized to produce vapor-liquid equilibrium. Subcritical
water remains fluid under very high heat and pressure and is an
extraordinary solvent. In these states, substances can rinse into tiny pits
and crevices and do quickly what a conventional extraction bath may take
years to accomplish.

At present, Clemson scientists have only one relatively small critical
fluid chamber. A larger one is being planned, and an even larger one is
needed in order to treat some of the bulky iron plates and guns from the
two Civil War vessels. Because of the high temperatures and pressures, the
chambers must be made with expensive "space-age" metals.

"Getting more funding is what we need now to scale up our recent successful
tests," said Cook, who has also been assisted in the Monitor conservation
project by David Burdige, ODU professor of ocean, earth and atmospheric
sciences and an expert in marine sediments.

The Mariners' Museum will open its $30 million USS Monitor Center in March
of next year. Its attractions will include some conserved artifacts, but
most of the recovered material will be on view only in the conservators'
water tanks. The center, however, does feature a replica of the Monitor
that visitors will be able to tour.

Cook said that even under the best-case scenario, the conservation of
artifacts already recovered could take a decade or so. The most difficult
conservation job will involve the Monitor's steam engine, which is made of
several different metals.

The conservation effort and the raising of other Monitor artifacts will be
hastened, Cook said, only if new technologies show superior results. "But
getting scientists involved in the conservation programs is difficult,
probably because of the poor track record of funding availability in this
area," he added. "Conservation is typically not a topic of scientific
research. Our partnership of ODU and Clemson researchers, together with The
Mariners' Museum and the Friends of the Hunley organization, is a very new
mindset in the conservation area."

The Union battleship Monitor was discovered in 1973 about 240 feet below
the surface of the Atlantic Ocean. It had sunk in a storm in December 1862,
just a few months after its historic, indecisive battle with the ironclad
CSS Virginia (formerly the Merrimack) in Hampton Roads. (The Confederates
ran the Virginia aground and destroyed it so it would not fall into enemy

What schoolchildren come to know as the Civil War battle of the Monitor and
the Merrimack signaled a shift in battleship construction from wood and
sail to iron and steam. The Monitor also was the first navy vessel to have
a turret allowing 360-degree cover by its guns.

This article was posted on: November 28, 2006

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