This 17th Century Warship That Was Recovered is Slowly Deteriorating in A Museum
In 1628, the Swedish warship Vasa set off on its maiden voyage from Stockholm harbor towards Poland, where a war was raging in the Baltic.
Commissioned by the King, 400 craftsmen built the 69-meter, richly decorated ship. It was fitted with 64 cannons, and upon completion, it was one of the most powerfully armed vessels in the world of the time.
Unfortunately, Vasa was too top heavy and dangerously unstable. Despite its instability, the king was eager to see her in battle and pushed her to sea.
On the day of departure, a crowd gathered at the harbor to see the ship off. The crew was permitted to take family and guests along for the first part of the passage. Over a hundred crewmen along with women and children were on board. After sailing just 1,300 meters, at the first strong breeze, the ship foundered, leaned over and sank. Around 30 people lost their lives.
The news of the sinking reached the Swedish king, who was in Poland, he wrote angrily to the Royal Council in Stockholm demanding that the guilty parties be punished. An inquiry was organized but in the end no one was found guilty of negligence and no one was punished.
After the ship’s valuable bronze cannons were salvaged, Vasa was mostly forgotten, until she was located and recovered from the shallow waters in 1961.
With a largely intact hull, the ship was housed in a temporary museum called Wasavarvet ("The Wasa Shipyard") until 1988 and then she was moved to the Vasa Museum in Stockholm.
The ship is one of Sweden's most popular tourist attractions, attracting more than a million visitors per year.
But in 2000, signs of deterioration sprang up on the ship’s surface. A new study shows that the ship’s wooden hull has significantly weakened due to decay of the wood’s structural fibers.
The Vasa wood is about 40 percent weaker than regular oak wood, and has become very acidic.
They're still not sure what's causing the decay, but one theory suggests that iron leaching out of the ship’s metal bolts and fixtures could be combining with oxygen to create a highly reactive substance that’s eating away the cellulose of the wood.
While some microbial degradation took place underwater, the researchers believe most of the decay happened after the ship was brought out of the water.
Soon after the ship was salvaged, it was sprayed with a waxy substance called polyethylene glycol (PEG), to replace the water inside the wood and prevent it from shrinking. It wasn’t intended to protect against fiber degradation, but it appears to have kept the ship’s surface better preserved than its inner regions.
In 2004, the museum upgraded its climate-control system to keep the relative humidity stable, as fluctuating humidity could lead to changes in the shape and weight of the ship. Efforts are also underway to replace the corroding steel bolts that were inserted in the ship during the 1960s with improved stainless steel ones.
The Vasa does not have an immediate risk of structural failure, the researchers concluded. Still, the ship deforms a few millimeters every year.
Given the extent of the wood atrophy, “It’s sort of a little bit too late to do anything,” said Bjurhager, who is focusing instead on preventing further deformation. Her team is currently working on a computer model of the ship so they can design a new support structure.