In August 1628, a Swedish warship sank within minutes of setting sail on its maiden voyage. This film documents the technical challenges involved in preserving the Wasa, which had been lost in Stockholm harbour for over three hundred years.In 1956, the unearthing of pieces of blackened oak led to the discovery of the Wasa, held fast in a grave of silt and slime. In an elaborate salvage operation it took three years to raise the ship clear of the seabed and move her to shallow water. It took a further two years to shore up the damaged stern and make it water tight for floating into dry dock. Although its timbers held throughout the move, they became exposed and vulnerable once they started to dry out. A constant stream of water had to be pumped over the ship to prevent the hull from disintegrating.Archaeologists cleared seven hundred tonnes of mud, which was sifted for treasures that would provide clues to why the Wasa sank. Hundreds more pieces recovered from the harbour, many of them elaborate sculptures that decorated the ship, explain a whole period of Sweden's history. A laboratory was built nearby for the work of preservation where every artefact, from intricate carvings to insignificant slivers of timber, was marked, measured and preserved.Over the centuries the waters of the Baltic chemically changed the outer layer of the wood, which would flake, crack and shrink beyond repair if allowed to dry without treatment. A substance was required to diffuse through the wood cells, forcing out the water, and setting hard, leaving it free to breathe during the final stage of drying. Research revealed a widely used petroleum product that met these demands. Polyethylene glycol, also used as a lubricant in the forming of metals and a base for ointments, hands creams and lipsticks, reinforces the wood cells and preserves the original shape of the Wasa.Artefacts and the hull itself are housed in a working museum where visitors can see the process of restoration. As more relics move from the laboratory to the museum a picture emerges of life aboard a Swedish warship. Although it is now clear that ineffective design made it unstable, the Wasa remains an excellent example of 17th century craftsmanship.
