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Ammonia Treatment of Acidic Vasa Wood
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2009 (English)In: Proceedings 10th ICOM-CC WOAM Conference, Amsterdam 2007 / [ed] Per Hoffmann, Bremerhaven, 2009, 539-561 p.Conference paper, Published paper (Other academic)
Abstract [en]

Outbreaks of acidic sulfate salts have been reported in numerous areas on the wooden surfaces of the Swedish historical shipwreck Vasa (from 1628) in the Vasa Museum. Effects of ammonia vapour treatment to reduce the acidity in Vasa wood, similar to that previously applied to the Dutch East Indiaman Batavia (from 1629), have been investigated by means of solid state 13C-NMR and MALDI-TOF spectrometry. No major changes were found in the molecular weight distribution of the bulking agent polyethylene glycol (PEG) or in the crystallinity of pulp cellulose after mild exposure to ammonia vapour. Further studies on the long-term pH stability and the post-treatment properties of the wood using spectroscopic methods and mechanical testing are in progress.

Place, publisher, year, edition, pages
Bremerhaven, 2009. 539-561 p.
Series
ICOM, Committee for Conservation, Working Group on Wet Organic Archaeological Materials, 10
National Category
Other Basic Medicine
Research subject
Structural Chemistry
Identifiers
URN: urn:nbn:se:su:diva-25013ISBN: 978 90 5799 139-4 (print)OAI: oai:DiVA.org:su-25013DiVA: diva2:198719
Conference
10th ICOM-CC WOAM Conference
Note
Part of urn:nbn:se:su:diva-7627Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2010-01-15Bibliographically approved
In thesis
1. Sulfur-Related Conservation Concerns in Marine Archaeological Wood: The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa
Open this publication in new window or tab >>Sulfur-Related Conservation Concerns in Marine Archaeological Wood: The Origin, Speciation and Distribution of Accumulated Sulfur with Some Remedies for the Vasa
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Synchrotron-based sulfur spectroscopy reveals a common concern for marine archaeological wood from seawater: accumulation of reduced sulfur compounds in two pathways. The distribution of sulfur species in the oak wood cell structure was mapped by scanning x-ray spectro-microscopy (SXM). Organically bound sulfur was found within lignin-rich parts, identified mainly as thiols and disulfides by sulfur K-edge x-ray absorption near edge structure (XANES) spectroscopy. Particles of iron sulfides, which may form in the presence of corroding iron, appeared in wood cavities. Cores scanned by x-ray fluorescence (XRF) show that high sulfur accumulation is restricted to the surface layers for the Swedish shipwreck Vasa, while the distribution is rather uniform throughout the hull timbers of the Mary Rose, U.K. Laboratory experiments, exposing fresh pine to simulated seabed conditions, show that the organically bound sulfur develop in reactions between lignin, exposed by cellulose-degrading erosion bacteria, and hydrogen sulfide produced in situ by scavenging sulfate reducing bacteria. With bacteria inoculated from shipwreck samples also iron sulfides formed. The iron sulfides oxidise in high humidity, and are the probable main cause of the numerous outbreaks on the Vasa’s hull of acidic sulfate salts, which were identified by x-ray powder diffraction (XRD). The iron ions catalyse several wood-degrading oxidative processes. Multi-elemental analyses were performed by scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (ESCA). The present amounts of total S remaining in the Vasa and the Mary Rose are estimated to at least 2 tonnes. After the Vasa´s spray treatment with polyethylene glycol solutions ceased in 1979, the continuing oxidation processes are estimated to have produced 2 tonnes of sulfuric acid in the wood. Laboratory experiments to gently neutralize acidic Vasa wood by ammonia gas have been conducted with promising results.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2008. 105 p.
Keyword
Sulfur accumulation, marine archaeological wood, Vasa, acidity, iron, ammonia, x-ray spectroscopy, cellulose
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-7627 (URN)978-91-7155-624-0 (ISBN)
Public defence
2008-06-03, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 09:30
Opponent
Supervisors
Available from: 2008-05-13 Created: 2008-05-09 Last updated: 2011-01-11Bibliographically approved

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