The degradation of wood in old Indian Ocean shipwrecks

The Effects of the Ammonia Neutralizing Treatment on Marine ArchaeologicalVasaWood

“…The bands in the 1200-1600 cm -1 part of the spectra arise primarily from lignin. The characteristic absorption bands of lignin are at 1592 cm -1 and 1509 cm -1 and these two absorptions are caused by C=C stretching vibrations of the lignin matrix, probably associated with aromatic ring deformation modes [18,22]. The absorption around 1592 cm -1 can be easily impaired by water present in the sample, thus the intensity of the lignin absorption band at 1509 cm -1 is the better choice for the determination of the lignin content in wood.…”

“…However, many of these bands are highly mixed and coupled vibrations and it is not always possible to assign them to specific functional groups and many overlap with peaks from the PEG spectrum. However, the band at 896 cm -1 represents a β-anomeric linkage between discrete cellulose and hemicellulose units which can be used to determine the content and degree of deterioration of carbohydrates in wood [20][21][22]. The bands in the 1200-1600 cm -1 part of the spectra arise primarily from lignin.…”

Analytical Aspects of Waterlogged Wood in Historical Shipwrecks

“…30,31,42 With solid state 13 C NMR that employs cross-polarization and magic-angle spinning (CP/MAS), structural and chemical differences between modern and archaeological wood can be studied both qualitatively and quantitatively. 31,43 For example, the resonance peaks from hemicellulose at ~21 and ~173 ppm were virtually absent in archaeological ligno-cellulosic material from Greece, indicating the degree and type of degradation (chemical lysis or biodeterioration). 42 CP/MAS 13 C-NMR spectroscopy can also be useful for evaluating possible effects on the cellulose crystallinity in wood samples from shipwrecks exposed to ammonia.…”

“…25 However, difficulties arise when comparing data obtained from different temperatures and pyroprobes. 31 With MALDI-TOF MS (matrix assisted laser desorption ionization-time of flight mass spectrometry) the consolidation agent PEG has been analyzed for possible signs of degradation after exposing Vasa wood samples to ammonia vapor to neutralize the acids. 40 Similar analyses indicated signs of PEG degradation in oxidative processes catalyzed by iron ions within timbers of different shipwrecks.…”

“…[29][30][31] By means of a diamond anvil cell it is possible to acquire semi-quantitative spectra related to the peak heights of certain wood components. Softwood and hardwood can be identified from their characteristic lignin components, and the content of lignin (Klason lignin structure) can be determined.…”