Freeze-drying history
A&M Archaeologists find a way to accelerate preservation of 17th-century shipwreck
Allan Turner
Source : http://www.chron.com/disp/story.mpl/metropolitan/7315090.html
COLLEGE STATION — Since its discovery in Matagorda Bay 15 years ago, the French ship La Belle has yielded a treasure trove of artifacts that offer unprecedented insight into 17th-century exploration of the New World.
Weapons, trade goods, medical and navigational instruments — part of the approximately 1 million items plucked from the bay bottom — have found homes in Texas museums.
But the biggest, arguably most significant recovery — a massive section of the ship's oak hull — has remained out of sight, submerged in a tank of preservative at Texas A&M University's nautical archaeology conservation lab.
The process of replacing water in the sodden timbers with polyethylene glycol, begun in 2004, could have taken up to nine more years to complete. But now, with the purchase of what is thought to be the hemisphere's largest archaeological freeze-dryer, conservationists believe they have found a better, cheaper way to finish the work in far less time.
In coming months, segments of the ship's 54-foot-long, 14-foot-wide hull, will be transferred to the dryer for processing. In October 2013, the newly conserved hull will be unveiled at Austin's Bob Bullock State History Museum, where it will be reassembled - in view of museum visitors - over a 10-month period.
The hull will be the centerpiece of a 6,000-square-foot exhibit on the Belle and its role in French exploration of Texas.
Sank in 1686
The ship, one of four explorer Robert Cavelier, Sieur de La Salle, brought to America in search of the Mississippi River's mouth, sank in Matagorda Bay in 1686.
Texas Historical Commission nautical archaeologists discovered the Belle's remains in 1995, calling them one of the New World's most exciting shipwrecks.
"The exciting thing about the hull reaching completion, aside from the conservation of a major artifact, is that it's an icon of an event that transformed Texas history," said Jim Bruseth, historical commission archaeology director. The ship's sinking, he said, contributed to the failure of La Salle's Fort Saint Louis colony near present-day Inez and opened the door to Spanish domination of the region.
"We could very well have been a state with a French heritage," Bruseth said.
He named Louisiana
La Salle is best known for his 1682 expedition down the Mississippi in which he claimed the land for King Louis XIV and named it Louisiana. In 1687, he was murdered during a mutiny of his men in Grimes County while engaged in an overland hunt for the Mississippi.
The discovery of the Belle provided a clear look at what explorers might pack to supply infant colonies and at construction techniques employed by 17th-century ship builders.
Conserving the ship's hull, said Peter Fix, a Texas A&M anthropology research associate who is lead conservator for the Belle, has been an arduous and increasingly costly undertaking.
The recovered hull, representing about 35 percent of the ship's underwater section, was heavily damaged by worms, bacteria and chemical reactions with seawater, he said. And, after more than three centuries beneath the bay, its wooden parts were saturated with water. "You could squeeze it like a sponge," Fix said.
On dry land, without conservation, the hull would have begun shrinking, warping and cracking within hours, he said.
For more than two years, the hull was immersed in fresh water to leach salt from its beams. During that time, Fix and his associates hand-cleaned, inch by inch, the boards of encrustations.
'Cost-effective' solution
In 2001, the A&M team, funded by the historical commission, began re-assembling the hull. Three years later, the reconstructed hull was submerged in polyethylene glycol.
At first, Fix's team got the petroleum-based preservative free, then, as its cost rose, at cost. But expenses continued to soar - raising the estimated cost of the process from $330,000 to more than $1.5 million - and conservators were forced to consider other options.
In summer 2008, the A&M team, with the sponsoring historical commission's support, began looking into freeze-drying.
"It was much more cost-effective," Fix said. "On the scientific side, freeze-drying is better for the timbers. There will be less maintenance necessary in the museum, less possibility for chemical interactions."
On the aesthetic side, Bruseth added, the finished hull will appear more natural. Polyethylene glycol leaves wood dark and waxy, he said.
The $500,000 cost of the 40-foot-long freeze-dryer, which will shiver the Belle's timbers at minus 40 degrees Celsius, was covered by the historical commission.
In addition to use in future conservation projects, the machine may be employed to salvage books, documents, furniture and other items damaged in Texas floods.