By Shawna Williams
|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
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
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.
So what’s eating the Vasa? Sulfuric acid is the villain
here, researchers found. Sandstrom hopes that with more analysis, they can
identify what is hastening the acid formation, and find better ways to