Contact with oxygen, in conjunction with the high humidity of the museum environment, causes these contaminants to produce sulfuric acid, according to a new doctoral thesis in chemistry from Stockholm University.
The Vasa sank in Stockholm's harbour on her maiden voyage in 1628 and was salvaged in 1961. The impressively restored ship is, after conservation, on display in the Vasa Museum in Stockholm. At present over 2,000 acidic sulfate salt precipitates have been registered in the timbers of the wreck as a result of the sulfuric acid formation. In her doctoral thesis from Structural Chemistry at Stockholm University, Yvonne Fors indicates that sulfur contaminants are a common conservation concern for marine archaeological wood. Her thesis presents the background, consequences and some remedies for these processes.
The seawater at the Vasa's wreck site became heavily polluted over the course of time and bacterial degradation of organic waste from the growing city consumed most of the oxygen in the water. Malodorous hydrogen sulfide was produced by scavenging bacteria, resulting in the accumulation of different sulfur and iron compounds in the wreck's timbers during 333 years on the seabed.
"In the Vasa high sulfur concentrations are found only in the surface layers of the timbers, while for other shipwrecks such as the Mary Rose in Portsmouth, England, sulfur has penetrated throughout the hull. There are more than two tonnes of sulfur in each of them", says Yvonne Fors, who has studied how sulfur passes from seawater into the timbers. Advanced x-ray spectroscopic analyses at international research facilities in USA and France were used to map the distribution of the sulfur and iron compounds in the wood cells of the timber. Through contact with oxygen and high humidity conditions sulfur and iron compounds may develop sulfuric acid. Presently, there is approximately two tonnes of sulfuric acid in the Vasa's wood.
"It is essential to find out as much as possible about how and where the different compounds are bonded in the cell structure of the timber in order to be able to predict their reactivity and the possibility of removing them," says Yvonne Fors. It appears that the sulfur and iron contaminants can only be partially extracted, without seriously damaging the fragile wood. "It is important to keep a stable climate in the museum to slow down the processes," says Yvonne Fors. High acidity can have a long-term detrimental effect on the strength of the timber, and this must be limited. Yvonne Fors has carried out some promising initial experiments neutralising the acid in loose pieces from the Vasa by means of ammonia gas. However, any possible side effects on the wood must be carefully evaluated. The discoveries and conclusions in this thesis are an important first step in prolonging the expiration date of this national treasure.The title of the thesis: Sulfur-Related Conservation Concerns for Marine Archaeological Wood. The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa.
The Swedish warship Vasa sank on her maiden voyage in the mouth of the Stockholm harbour on the 10th of August 1628. The Vasa was fitted with what were then the most powerful armaments carried by any ship in northern Europe, and was sent to help the Swedish King Gustav II Adolf in the struggle for control over the Baltics. However, the ship lacked stability and keeled over in a gust and sank to a depth of thirty-two meters after sailing for just over a kilometre. The hull was salvaged in 1961, 333 years later, during a remarkable diving operation, and is now on display in the Vasa Museum in Stockholm.
Maria Erlandsson | idw
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences