Featured Research

from universities, journals, and other organizations

Degradation Of Wood In Royal Warship Vasa Is Caused By Iron

Date:
September 30, 2008
Source:
Vetenskapsrådet (The Swedish Research Council)
Summary:
During its time in the sea bottom of Stockholm harbor, huge amounts of iron and sulfurous compounds accumulated in the wood of the royal warship Vasa. Since 2000 it has been noticed that changes are taking place in the wood, changes that threaten the stability of the ship.

The warship Vasa, Stockholm, Sweden.
Credit: Image courtesy of The Vasa Museum

During its time in the sea bottom of Stockholm harbour, huge amounts of iron and sulfurous compounds accumulated in the wood of the royal warship Vasa. Since 2000 it has been noticed that changes are taking place in the wood, changes that threaten the stability of the ship.

At first it was believed that the conversion of sulfur to sulfuric acid was the culprit, but now it has been shown that it is the iron from the ship’s rusted bolts and cannonballs is causing the most serious deterioration of the wood. This is the subject of a dissertation by Gunnar Almkvist from the Swedish University of Agricultural Sciences.

The wood in the royal ship Vasa has been seriously affected by the biological and chemical processes that the hull was exposed to during its period under water (1628-1961), during its conservation period (1962-1989), and subsequently in its modern museum setting.

Iron and sulfurous compounds (a total of 5-10 tons) were incorporated in the wood through natural processes when the ship lay on the sea bottom of Stockholm harbour.

The sulfur comes from the degradation of Stockholm’s unpurified sewage on the oxygen-free bottom, while the iron primarily comes from the bolts that held together the hull and other iron objects onboard, such as cannonballs. In the subsequent conservation, the wood was treated with huge amounts of polyethylene glycol (PEG) and fungicides.

During the rainy summer of 2000, the humidity varied dramatically inside the museum, and during this time white and yellow precipitates were discovered on the ship. These deposits turned out to be acidic sulfur and iron compounds, and it was concluded that sulfur in the wood had been converted into sulfuric acid. Concern about what was happening to the Vasa led to a commitment to pursue research into the causes and how they could be prevented.

Gunnar Almkvist and his colleagues have now completed a thorough examination of the chemical degradation processes in the wood, and it turns out that it is the iron that is the main culprit, not the sulfur.

The most serious problem is that the wood substances have begun to be degraded at some depth in the lumber and that this degradation has also affected the conservation agent (PEG). Analyses show that the wood is extremely acidic in places where the scientists found degradation.

The low pH level is a result of the formation of organic acids such as formic acid and oxalic acid with the degradation of wood components and PEG. In these sections there are only tiny amounts of sulfur. Certain types of sulfurous compounds appear to have a protective effect when the wood is in much better condition where there is a great deal of sulfur.

Everywhere there has been degradation, on the other hand, there is plenty of iron, and this iron has proven to be in a form that is highly mobile and chemically active. Iron can vary in its oxidation levels and then can take on special properties and participate in special reactions.

In the presence of oxygen or other oxidation agents, iron ions can form so-called radicals. These are very short-lived but highly reactive and can attack most biological substances. The theory is therefore that the iron is catalyzing (hastening) the formation of radicals in the wood of the Vasa. Sulfur, on the other hand, can function as an antioxidant that captures radicals and prevents them from reacting with the wood or with PEG. The element that was originally thought to be the threat thus appears to be a safeguard.

The dissertation also reports from attempts to extract iron compounds from the Vasa wood. The results show that this is possible, though very time-consuming. In the process, other water-soluble compounds are also extracted and acids are neutralized. The method can be successfully used for smaller objects and can also be developed for the treatment and conservation of waterlogged archeological wood.

Link to the complete dissertation: The Chemistry of the Vasa - Iron, Acids and Degradation: http://diss-epsilon.slu.se/archive/00001809/


Story Source:

The above story is based on materials provided by Vetenskapsrådet (The Swedish Research Council). Note: Materials may be edited for content and length.


Cite This Page:

Vetenskapsrådet (The Swedish Research Council). "Degradation Of Wood In Royal Warship Vasa Is Caused By Iron." ScienceDaily. ScienceDaily, 30 September 2008. <www.sciencedaily.com/releases/2008/09/080925083203.htm>.
Vetenskapsrådet (The Swedish Research Council). (2008, September 30). Degradation Of Wood In Royal Warship Vasa Is Caused By Iron. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2008/09/080925083203.htm
Vetenskapsrådet (The Swedish Research Council). "Degradation Of Wood In Royal Warship Vasa Is Caused By Iron." ScienceDaily. www.sciencedaily.com/releases/2008/09/080925083203.htm (accessed October 20, 2014).

Share This



More Matter & Energy News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) — Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) — Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) — Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
What We Know About Microsoft's Rumored Smartwatch

What We Know About Microsoft's Rumored Smartwatch

Newsy (Oct. 20, 2014) — Microsoft will reportedly release a smartwatch that works across different mobile platforms, has a two-day battery life and tracks heart rate. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins