Light load: Freeze-drying a supply ship

by The Canadian Press

BRYAN, Texas: More than three centuries ago, a French explorer’s supply ship sank in the Gulf of Mexico, taking with it France’s hopes of colonizing a vast piece of the New World—modern-day Texas.

Like Rene-Robert Cavelier Sieur de La Salle in 1685, researchers at Texas A&M University are in uncharted waters as they try to reconstruct his vessel with a gigantic freeze-dryer, the first undertaking of its size.

By placing the ship —La Belle—in a constant environment of up to -51C (-60F), more than 300 years of moisture will be safely removed from hundreds of European oak and pine timbers and planks. The freeze-dryer, located at the old Bryan Air Force base several miles northwest of College Station, Texas, is 12m (40ft) long and 2.5m (8ft) wide, the biggest such machine on the continent devoted to archaeology.

Researchers will then rebuild the 16.5 metre (54.5ft) vessel, which will become the centerpiece of the Bob Bullock Texas State History Museum in Austin.

From a historical perspective, it’s “an icon of a small event that dramatically changed the course of Texas history,” said Jim Bruseth, who led the Texas Historical Commission effort to recover the remains.

The supply ship was built in 1684 and sank two years later in a storm on Matagorda Bay, about midway between Galveston and Corpus Christi.

“When La Belle sank, that doomed La Salle’s colony and opened up the door for Spain to come in and occupy Texas,” Bruseth said. “People can see firsthand how history can turn on a dime.”

“It’s an important piece in ship architecture,” said Peter Fix, conservator at the school’s Centre for Maritime Archaeology and Conservation. Researchers have determined that unlike earlier vessels, the frames on La Belle were marked specifically by the French craftsmen so the wood comprising the hull could follow the complex curve of the ship.

“This was the age of Enlightenment when math was coming into more play,” Fix said.

After a more than decade-long hunt, Texas Historical Commission archaeologists found it in 1995 in 3.7m (12 ft) of murky water. Then began the tedious recovery that involved constructing a dam around the site.

After the water was pumped out, teams dug through up to 1.8m (6ft) of mud in the Gulf of Mexico seabed to retrieve the nearly intact ship and some 700,000 items, from swords, cannons and ammunition to beads and mirrors intended for trade. Archaeologists also found one skeleton, believed to be a crew member or settler among the some 40 people aboard.

The ship was then transferred to the Texas A&M lab, where the water-logged wood has been immersed in a chemical solution to keep it solid.

Initially, the ship was being reassembled in a two-stage chemical process, but as oil prices rose, so did the cost of the key chemical, polyethylene glycol. They decided the freeze-dry process was more economical and would shorten the preservation timeframe. So, the hull was disassembled and the wood was categorized and digitally scanned so that they could make moulds of its original shape.

A New York-based firm that specializes in scientific equipment built the submarine-like freeze dryer.

“If we were to take any piece of wood, say it’s been in the water for 300 years, and pull it out, it would shrink, crack, warp within a couple of days,” Fix said. “The physical stress on wood would essentially cause it to fall apart and crumble and powder into pieces.”

But scientists know that at the right temperature and pressure, water can go from being solid to gas and skip the liquid phase.

“It’s a slow, controlled process and depending on the thickness of material, over four to six or seven months, we know that timber has lost most of its bound water and it’s safe to bring out,” Fix said, noting that they’re experimenting with smaller pieces to “make sure nothing goes wrong.”

A similar preservation using freeze-dryer technology is planned for a medieval ship discovered in 2002 in Newport, South Wales. That vessel is about twice the length of La Belle.

The La Belle rebuilding will start late next year at the Bullock Museum.

“I can’t wait,” said Bruseth, who is serving as guest curator for the exhibit. “It’s just fantastic to see this project reach the point where we’ll actually be reassembling the ship as a permanent installation.”

La Salle was the first European to travel the Mississippi River south to the Gulf, claiming all the land along the Mississippi and its tributaries for France in 1682. In 1685, he sailed from France with more than 300 colonists aboard four ships, La Belle among them, to establish a settlement at the mouth of the Mississippi.

Maps of the time show he believed the river was closer to Mexico, and his expedition missed the Mississippi by hundreds of miles.

“They were guessing,” Bruseth said.

His team established a colony near Matagorda Bay, but it was ravaged by disease, rattlesnakes and Indians. Three years later, La Salle led a handful of survivors inland in search of the Mississippi. The explorer didn’t make it out of Texas; he was murdered by his own men.