Gallo-Roman craft restored thanks to freeze drying.

A 32 m long barge weighing 30 tonnes that sank in the Rhone around 50 AD is being restored by soaking in polyethylene glycol, followed by freeze drying.

"Arles-Rhône 3" was discovered in 2004 in the Roman port of Arelate, near Arles in the South of France. Its hulk and part of its equipment remained virtually unaltered for almost 2000 years, protected by a thick layer of silt. It was cut into several segments and in order to preserve the wood, which then had a remarkable appearance, but a texture similar to that of a sponge, had to be dipped in a series of increasingly concentrated ethylene-glycol resin baths (first at a concentration of 20%, then 40%), in order to gradually replace the water with resin.

After this, the elements were freeze dried in order to vaporize the water, without it going through a solid ice phase, given that a classic drying process would not have made it possible to save the boat, which is to be exhibited, thanks to a metal frame, starting in spring 2013 in Arles.

Monitor progress: www.arles-rhone3.fr

La Recherche, January 2012.