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Steindal, Calin Constantin & Braovac, Susan-Diana
(2022).
The degradation of conserved archaeological wood in the presence of pyrite - An analytical protocol.
Show summary
The StAr Project (Development of Storage and assessment methods suited for organic archaeological artefacts) within the framework of Joint Programming Initiative on Cultural Heritage and Global Change (JPI-CH) Conservation, Protection and Use, seeks to establish an analytical assessment protocol suited for museums, using well-established analytical techniques to observe the extent of degradation of archaeological wood containing unstable inorganic compounds. The assessment of the post-treatment condition of conserved archaeological wooden artefacts would allow identification of early stages of degradation, leading to earlier and more cost effective mitigation measures to be applied.
The role of pyrite oxidation in the degradation of archaeological collections is well documented. In the presence of oxygen, pyrite oxidizes producing sulphuric acid and hydrates of iron(II) sulphate. Sulphuric acid causes extensive depolymerisation of cellulose and hemicellulose, reducing mechanical strength, while the iron(II) sulphate adsorbs water from the atmosphere, further enhancing oxidation. Additionally, the high amounts of iron(II) and iron(III) ions also degrade polyethylene glycol (PEG), which is often used as a conservation agent to support the wood cells before drying.
This paper presents our methodological efforts in analyzing wood samples from several objects and excavation sites, treated by different conservation treatments, both standard and newer (PEG, and the polyester-based ‘Nucléart’, respectively). Combining powder X-ray diffraction (XRD) with scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), infrared spectroscopy and pH measurements, we sought to elucidate the state of pyrite oxidation and wood degradation. XRD patterns revealed the presence of complex inorganic mixtures, often dominated by the presence of gypsum, and iron sulphate in different oxidation and hydration states along with unoxidized pyrite. Moreover, IR spectra of wood revealed degradation of the holocellulose fraction, while lignin appears less affected.
Key words: Archaeological wood, pyrite, oxidation, sulphate, degradation
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Braovac, Susan
(2019).
Practical experiences with cross-disciplinary research - the case of Saving Oseberg.
Primitive tider.
ISSN 1501-0430.
21,
p. 143–148.
Full text in Research Archive
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Wakefield, Jennifer M.K.; Steindal, Calin Constantin; Piva, Eleonora; Stockman, R; Adams, Gary & Heinze, T
[Show all 8 contributors for this article]
(2019).
Investigation of natural polymers for treatments of Oseberg artifacts-review of lab degraded and archaeological wood.
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Lucejko, Jeannette J.; Sahlstedt, Malin; McQueen, Caitlin; Modugno, F & Braovac, Susan
(2019).
Comparative chemical investigations of alum treated archaeological wood from different museum collections.
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Lucejko, Jeannette J.; McQueen, Caitlin; Braovac, Susan; Sahlstedt, Malin; Modugno, F & Caruso, Francesco
[Show all 8 contributors for this article]
(2019).
Acid-catalyzed hydrolysis of paper in contact with acidic wood.
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McQueen, Caitlin; Braovac, Susan; Lucejko, Jeannette J. & Modugno, F
(2019).
Unexpected ammonium compounds in alum-treated wood from the Oseberg collection.
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Braovac, Susan; Sahlstedt, Malin & Wittköpper, Markus
(2019).
Retreatment testing of alum-treated woods from the Oseberg collection – results from first trials.
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McQueen, Caitlin; Steindal, Calin Constantin & Braovac, Susan
(2018).
Temperature- and RH-induced changes in materials related to alum-treated wood – a qualitative X-ray diffraction study.
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Lucejko, Jeannette J.; Braovac, Susan; McQueen, Caitlin; Modugno, F & Colombini, Maria Perla
(2018).
The catalysing effect of alum in degradation processes of carbohydrates in archaeological wood.
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McQueen, Caitlin; Tamburini, Diego & Braovac, Susan
(2017).
FTIR microscopy for analysis of treated archaeological wood samples.
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Andriulo, Fabrizio; Giorgi, Rodorico; Steindal, Calin Constantin; Kutzke, Hartmut; Braovac, Susan & Baglioni, Piero
(2016).
Nanotechnologies for the restoration of alum-treated archaeological wood.
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McHale, Emily; Steindal, Calin Constantin; Braovac, Susan; Gillis, Richard; Adams, Gary & Benneche, Tore
[Show all 7 contributors for this article]
(2016).
Synthesis and characterisation of lignin-like oligomers as a bio-inspired consolidant for waterlogged archaeological wood.
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Braovac, Susan; McQueen, Caitlin; Andriulo, Fabrizio; McHale, Emily & Steindal, Calin Constantin
(2016).
The Saving Oseberg Project – Chemistry for the salvation of Viking Age wooden artefacts.
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McQueen, Caitlin; Kutzke, Hartmut & Braovac, Susan
(2016).
Identification of metal compounds in alum-treated wood from the Oseberg collection.
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McHale, Emily; Braovac, Susan; Steindal, Calin Constantin; Kutzke, Hartmut & Benneche, Tore
(2016).
Consolidation of waterlogged archaeological wood with lignin-like oligomers.
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Hauer, David; Andriulo, Fabrizio; McQueen, Caitlin; Braovac, Susan; Steindal, Calin Constantin & Kutzke, Hartmut
[Show all 7 contributors for this article]
(2015).
Håper at vikingskattene kan reddes.
[TV].
NRK Dagsrevuen.
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Tamburini, Diego; Lucejko, Jeannette J.; Modugno, Francesca; Colombini, Maria Perla; Kutzke, Hartmut & Braovac, Susan
[Show all 9 contributors for this article]
(2015).
The ArCo Project - Ageing Studies of Treated Composite Archaeological Waterlogged Artefacts - preliminary results.
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McHale, Emily; McQueen, Caitlin; Christensen, Mikkel; Braovac, Susan; Næss, Ellen Marie & Hauer, David
(2015).
Barnesøndag: Oseberglaboratoriet (Family day: The Oseberg Laboratory).
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McQueen, Caitlin; Kutzke, Hartmut & Braovac, Susan
(2015).
Metal ions in archaeological wood from the Oseberg find – a complex issue?
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Tamburini, Diego; Lucejko, Jeannette J.; Modugno, Francesca; Colombini, Maria P.; Kutzke, Hartmut & Braovac, Susan
[Show all 9 contributors for this article]
(2015).
PY-GC-MS with in situ silylation to the analysis of treated composite archaeological wood artifacts - the ArCo project.
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Tamburini, Diego; Braovac, Susan; Lucejko, Jeannette J.; Modugno, Francesca; McQueen, Caitlin & Kutzke, Hartmut
[Show all 7 contributors for this article]
(2015).
Chemical analysis of degraded wood by Py-GC/MS and ICP-AES.
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McHale, Emily; Benneche, Tore; Kutzke, Hartmut; Christensen, Mikkel & Braovac, Susan
(2014).
Preservation of archaeological wood: a challenge for biomimetic materials.
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Braovac, Susan; Bill, Jan & Løchen, Ragnar
(2013).
Åndenes Makt.
[TV].
TVNorge.
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Braovac, Susan; Lucejko, Jeanette J.; Tamburini, Diego; Kutzke, Hartmut & Colombini, Maria P.
(2013).
Saving Oseberg - Research for Preservation. Analysis of Highly Deteriorated Archaeological Wooden Objects by Py (HMDS) - GC/MS.
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Kutzke, Hartmut; Braovac, Susan; Christensen, Mikkel & Gjengedal, Kjerstin
(2012).
Nasjonalskatt går i oppløysing.
[Newspaper].
Apollon.
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Braovac, Susan; Kutzke, Hartmut; Jørgensen, Sissel; Bouzga, Aud Mjærum; Hansen, Eddy Walther & Arstad, Bjørnar
(2012).
ALUM-TREATED WOOD: CHARACTERIZATION USING INFRARED SPECTROSCOPY AND SOLID STATE NMR.
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Kutzke, Hartmut; Christensen, Mikkel & Braovac, Susan
(2012).
Hvor fortid og fremtid møtes - med forskerlupe i Osebergfunnet.
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Bisulca, Christina; Odegaard, Nancy; Braovac, Susan & Kutzke, Hartmut
(2011).
Consolidation of Alum-Treated Wood with Alkoxysilanes.
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Kutzke, Hartmut; Braovac, Susan & Christensen, Mikkel
(2011).
Kunsten å bevare vikingkunst - ingen enkel kunst. Preserving the objects from Oseberg.
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Lehmann, Eberhard; Mannes, David; Hunger, K.; Wörle, Marie; Braovac, Susan & Kutzke, Hartmut
[Show all 7 contributors for this article]
(2011).
Wood investigations by means of radiation transmission techniques in the analysis of cultural heritage objects of different size scale.
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Kutzke, Hartmut; Braovac, Susan; Christensen, Mikkel & Hansen, Finn Knut
(2011).
Old treatments – new solutions? Summary of activities of the Alum Research Group.
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Kutzke, Hartmut; Braovac, Susan & Euler, Harald
(2011).
The behaviour of alum in alum-conserved wooden objects.
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Braovac, Susan; Jensen, Maria; Aarseth, Bjarte Einar; Bill, Jan; Hjulstad, Guro & Løchen, Ragnar
[Show all 9 contributors for this article]
(2011).
Long term responses in archaeological wood to ambient temperature and relative humidity – case study: the Oseberg Ship.
Show summary
INTRODUCTION
The Oseberg ship, dated from ca 815-820 AD, is one of the most important discoveries of the Viking age period in Norway. The fact that the ship consists of 90 % original material makes it a unique find with no comparison elsewhere in the world. The ship is 21.5 meters long, built with radially cut, 3 cm thick oak planks and is 5 meters at its widest. In 1904 the waterlogged wood was conserved with linseed oil and creosote and the surface exterior was then lacquered. Over 2000 pieces were used for the reconstruction of the ship with the use of both original and modern screws together with adhesive.
The Oseberg ship, displayed at the Viking Ship Museum in Oslo, has been subjected to an uncontrolled climate since 1926, with only heating in winter. The display area is therefore influenced by seasonal changes in relative humidity (RH), which rises above values of 70% RH in summer, and drops below 30% RH in winter. Rapid changes over the course of a few hours have also been recorded.
EXPERIMENTAL RESULTS
Continuous monitoring of dimensional change due to RH fluctuations has been carried out on two planks of the ship and on two samples free to warp. To our knowledge, it is the first example of long term hygro-mechanical monitoring on an archaeological wooden artifact. Through this approach it is possible to show the specific sensitivity to RH fluctuations; restrained planks show the least response, while unrestrained samples have highest response to RH changes.
The analysis of the data obtained after fifteen months of continuous logging allows us to quantify the specific “sensitivity” of the wood, which can be useful in determining the threshold of allowable RH fluctuations.
The results of stress on the free samples in the exhibition site will be discussed. It is also planned to measure the forces absorbed by the restrained samples so that long-term mechanical effects of absorbed stress can be understood better. These data are fundamental as a validation of future Finite Element simulations and hygromechanical modelling of deteriorated wood.
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Braovac, Susan; Kutzke, Hartmut; Jørgensen, Sissel; Bouzga, Aud Mjærum; Arstad, Bjørnar & Hansen, Eddy Walther
(2011).
Alum-treated wood: characterization using infrared spectroscopy and solid state 1h and 13C NMR.
Show summary
Abstract
The Oseberg find contains a large proportion of hardwoods that had been treated about 100 years ago with hot solutions of alum salts (potassium aluminum sulfate dodecahydrate, KAl(SO4)2 . 12H2O). Today, the wood is characterized by a high acidity (pH 1) and is structurally highly degraded. The observed deterioration is also active. The ‘alum treatment’ was a method of choice for the conservation of highly deteriorated waterlogged archaeological wood found from 1850 – 1950 and has since been replaced by treatment with polyethylene glycols (PEG). The alum treatment has been mainly used in Scandinavia but also in the USA, Japan and other European countries.
Attempts to chemically characterize the alum-treated wood from the Oseberg find is one phase in the research currently being undertaken at the Museum of Cultural History as a part of the Alum Research Project. The ultimate aim of this project is to design conservation re-treatments which will stabilize and strengthen the wood. So far, we have focussed on non-destructive analytical techniques using ATR-FTIR and solid state NMR. Further chemical analyses are planned, using destructive techniques.
Analyses using infrared spectroscopy and solid state 1H and 13C NMR were undertaken on selected alum-treated samples and compared with fresh woods as well as archaeological woods from the same find not treated with alum. The advantages of these analytical techniques lie in the fact that sample preparation is minimal prior to measurement – highly deteriorated wood can be greatly modified by standard sample preparation procedures. These techniques, when used together, give an acceptable level of qualitative structural information regarding the state of the remaining polymers.
Analytical results demonstrated that all alum-treated samples are highly degraded relative to archaeological wood from the same find not treated with alum salts. The non-alum-treated archaeological wood has carbohydrates left, which are highly reduced in the alum-treated wood. 13C NMR can distinguish different lignin types, and has shown that syringyl lignin is more deteriorated than guaiacyl lignin in the most deteriorated alum-treated samples. NMR and FTIR-ATR results also show that remaining polymers in the alum-treated wood, dominated by lignins, are highly oxidized and contain carboxylic groups. This shows that the alum-treatment has caused extensive chemical changes in the wood, resulting in wood with a powdery consistency with almost no structural integrity relative to samples from Oseberg not treated with alum.
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Christensen, Iben V.; Ottosen, Lisbeth M.; Jensen, Poul; Bojesen-Koefoed, Inger; Kutzke, Hartmut & Braovac, Susan
[Show all 8 contributors for this article]
(2010).
The use of an electric field for the removal of alum from treated wooden objects.
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Braovac, Susan & Kutzke, Hartmut
(2010).
Past Conservation Treatments and their Consequences – the Oseberg Find as a case study.
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Braovac, Susan; Christensen, Mikkel; Kutzke, Hartmut; Hartmann, Stefan; Mokso, Rajmund & Lehmann, Eberhard
(2010).
Looking inside! 3D imaging experiments on alum-conserved archaeological wood.
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Braovac, Susan; Christensen, Mikkel; Kutzke, Hartmut; Hartmann, Stefan; Mokso, Raimund & Lehmann, Eberhard
(2010).
Looking inside! 3D imaging experiments on alum-conserved archaeological wood.
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Christensen, Iben V.; Ottosen, Lisbeth M.; Jensen, Poul; Bojesen-Koefoed, Inger; Kutzke, Hartmut & Braovac, Susan
[Show all 8 contributors for this article]
(2009).
The use of an electric field for the removal of alum from treated wooden objects.
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Kutzke, Hartmut; Braovac, Susan & Christensen, Mikkel
(2009).
Historische Konservierungsmethoden als neue Herausforderung fuer die Archaeometrie: Die alaunbehandelten Holzobjekte des Osebergfundes.
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Dionisi Vici, Paolo; Aarseth, Bjarte Einar; Bill, Jan; Hjulstad, Guro; Jensen, Maria Malherbes & Løchen, Ragnar
[Show all 9 contributors for this article]
(2009).
In-situ deformation measurements on a large wooden archaeological artefact: the Viking Age Oseberg ship.
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Braovac, Susan & Kutzke, Hartmut
(2009).
The Presence of Sulfuric Acid in Alum-conserved Wood – Origin and Consequences.
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Braovac, Susan
(2008).
Rescuing the Oseberg Find, a Project in Progress. Alum-conserved Wood - Mechanisms of Deterioration and Development of Preservation Strategies.
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Braovac, Susan
(2008).
History of the Viking ship collections and their conservation challenges.
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Braovac, Susan & Olstad, Tone Marie
(2007).
Braovac, Susan, Tone Olstad, How to Move a Viking Ship: two conservators’ perspectives on the process leading to a decision.
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Braovac, Susan
(2007).
The Viking Ship finds: Preservation Challenges and the search for potential solutions.
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Braovac, Susan; Huth, Nadine & Løchen, Ragnar
(2006).
Rescuing the Oseberg Find, a project in progress: Alum-conserved wood – mechanisms of deterioration and development of preservation strategies.
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Vedeler, Marianne & Braovac, Susan
(2003).
Nytt liv i gamle magasiner.
Museumsnytt.
ISSN 0027-4186.
52(3).
