Stockholm University chemist Magnus Sandstrom looks on as Vasa Museum curator Lovisa Dal prepares a sample for analysis. (Photo courtesy of SciArts)

SSRL is helping provide clues to save the 400-year-old Swedish ship Vasa, preserved for centuries in Stockholm Harbor but now in danger of succumbing to air in the museum that houses it.

"The SSRL facilities were actually the key to solving the problem," said Magnus Sandstrom, a chemist from Stockholm University who came here to find what is causing the ship’s decay.

The massive Vasa warship, launched in 1628 in Stockholm Harbor, tipped over and sank soon after its launch. It was brought back up in 1961, and put in a specially built museum. Conditions in the harbor kept the ship well preserved while it was underwater, but a few years ago, after an exceptionally humid summer, a museum conservator noted discoloration on parts of the ship, a warning that decomposition was starting.

The story of the Vasa has drawn attention worldwide. When Sandstrom and a Vasa Museum curator, Lovisa Dal, came to SLAC in mid-December to make new measurements, the Scientific Arts Media department was asked to shoot some footage of the pair in action for a Swedish science television show.

This filming was "the second or third project we’ve done like this," said Chip Dalby (TIS), a member of the film crew. The crew sent about an hour of footage to Sweden, showing Sandstrom and Dal preparing and analyzing a sample, and talking about the process in Swedish.

To get samples from the ship for analysis, museum curators used a machine like those used to get core samples from living trees. They stored the samples in tubes filled with nitrogen, since exposure to oxygen could change the wood and make later measurements unreliable.

Before the wood samples could be analyzed, they first had to be filed into a fine powder and sandwiched between mylar tape and polypropylene film on an aluminum slide. Dal did this in a nitrogen-filled box. The slide was then put in a helium-filled X-ray sample chamber, where high-energy synchrotron radiation hit the sample and generated a spectrum. A computer analyzed the spectrum to find what elements were in the sample and in what chemical state they occurred at different depths from the surface of the wood.