A warship battles the enemy within

Shipwreck: Saved from a watery grave, the Vasa now has preservationists scrambling to stop a chemical reaction from destroying it from the inside.

Medicine & Science

December 29, 2003|By Scott Shane | Scott Shane,SUN STAFF

STOCKHOLM, Sweden - The mighty Swedish warship Vasa was - literally - a total flop on its maiden voyage in 1628. It keeled over and sank in minutes as thousands gathered for the occasion watched in horror.

But dredged up more than 300 years later from cold storage on the bottom of Stockholm's harbor, the vessel has enjoyed a remarkable second life as one of the world's great museum pieces.

Now the Vasa is under attack from a new enemy. Its ancient oak timbers are literally consuming themselves, being chewed up by sulfuric acid produced by the accidental chemistry of centuries-old sewage and dissolved iron bolts.

Preservationists at the Vasa Museum have rushed in with stopgap measures as rudimentary as spraying the ship with baking soda. Meanwhile, they're finding new ways to preserve old wood and developing scientific insights that may help save history around the world.

"The Vasa still has secrets left to reveal," writes Magnus Sandstrom, professor of structural chemistry at Stockholm University, in The Vasa's New Battle: Sulphur, Acid and Iron a booklet on the acid issue just published with two colleagues, Yvonne Fors and Ingmar Persson.

"When we understand the chemical processes, then we can find ways to counteract even the tooth of time."

The story of the fight to preserve the largest wooden object ever recovered from the sea - the Vasa is 226 feet long and weighs roughly 1,000 tons - must begin with the original catastrophe. In maritime history, perhaps only the Titanic's launch can rival the Vasa's for sheer hubris.

In 1628, the year of the Vasa's stillbirth, Sweden was near the height of its imperial power under King Gustavus II Adolfus, the Lion of the North. He was about to lead one of the world's most powerful militaries into Europe's Thirty Years' War and would eventually rule not only Sweden, but also Finland, Latvia, Estonia and part of Germany.

The Vasa was to be a worthy flagship for the Swedish navy. Built over three years in Stockholm shipyard from 1,000 oak trees, it was decorated with hundreds of painted wooden sculptures of figures from myth, the Bible and Swedish lore. It carried a formidable arsenal, including 48 cannon - firing 24-pound balls.

In retrospect, the arsenal was a bit too formidable. The ship's designers were masters of their craft, but innocent of the mathematics of calculating the balance of so big a ship. By adding a second gun deck, they doomed their masterpiece.

There were signs of impending disaster. To test the ship's stability while moored, construction overseers had 30 men run back and forth on the deck. After three tries, the experiment was halted because the Vasa was threatening to capsize.

A top admiral watching the test seemed paralyzed in the absence of the king. "If only His Majesty were at home!" declared Adm. Klas Fleming, according to later testimony. He let plans for the launch go ahead.

On August 10, 1628, crowds gathered to watch the magnificent vessel leave to meet the impatient king in Prussia. As the Vasa emerged from the lee of one of the islands on which Stockholm is built, wind caught the sails and it tilted dangerously. The ship righted itself, but with the next gust, "she heeled right over and water gushed in through the gun ports until she slowly went to the bottom under sail, pennants and all," according to a letter sent by the chagrinned Council of the Realm to give his absent king the bad news.

The Vasa's service ended after 20 minutes and less than a mile of travel, taking about 50 people to their deaths.

In the inquiry that followed, the Vasa's Danish-born captain was interrogated about what had gone wrong. "You can cut me in a thousand pieces if all the guns were not secured," said Sofring Hansson, according to the record preserved at the Vasa Museum. "And before God Almighty I swear that no one on board was intoxicated."

Divers soon salvaged many of the Vasa's guns, but the ship settled in the muck at a depth of 100 feet.

Several factors conspired to protect it. The low salinity of the Baltic was not hospitable to shipworms. The choking pollution of Stockholm harbor - which killed the fishing industry and contributed to cholera epidemics that killed 8 percent of the city's inhabitants during 1834 and 1835 - also fed bacteria that depleted the oxygen near the sea floor.

With little oxygen available, the bacteria drew oxygen from sulfate ions in sea water to decompose organic matter, creating a poisonous hydrogen sulfide byproduct that protected the ship from pests.

The Vasa was located in 1956 by a single-minded engineer, Anders Franzen, who had searched for it for years. He dropped a home-built sampling tool from a boat to a suspicious hump on the ocean bottom and brought back a tiny piece of black oak.

To bring the wreck to the surface, Franzen and his associates considered some wild ideas: freezing the ship in a huge block of ice and letting it float free, or stuffing it with Ping-Pong balls to force it to surface.

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