Freeze-drying History

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.

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.

Read more here.



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