Susan Braovac

• Cutajar, Michelle; Braovac, Susan-Diana; Stockman, Robert A.; Howdle, Steven M. & Harding, Stephen E. (2023). Evaluation of two terpene-derived polymers as consolidants for archaeological wood. Scientific Reports. 13(1). doi: 10.1038/s41598-023-29785-5. Fulltekst i vitenarkiv Vis sammendrag

  The evaluation of two terpene-derived polymers, termed TPA6 and TPA7, as possible consolidants for archaeological wood was carried out. The overall objective of this work was to expand the non-aqueous treatment toolkit which is available for the conservation of the highly degraded Oseberg collection. The wood artefacts which were found on the Oseberg ship were treated with alum in the early twentieth century, leading to the formation of sulfuric acid and to the precarious state that they are in today. Some of these artefacts cannot be treated with conventional aqueous consolidants, like polyethylene glycol, due to their highly degraded and/or reconstructed nature. This study sought to examine the level of penetration of the polymers in archaeological wood and to evaluate their consolidative effect. Both TPA6 and TPA7 were soluble in isopropanol and had a Mw of 3.9 and 4.2 kDa respectively. A number of archaeological wood specimens were immersed in solutions of these polymers. Their penetration and effects were evaluated using weight and dimensional change, colour change, infrared spectroscopy, scanning electron microscopy and hardness tests. Both polymers successfully penetrated the wood specimens, with a higher concentration found on the surface versus the core. Additionally, both polymers appeared to increase the hardness of the specimen surfaces. Increasing the polymer concentration and soaking time in future investigations could potentially facilitate the penetration to the wood cores.

• Cutajar, Michelle; Machado, Fabricio; Crucitti, Valentina Cuzzucoli; Braovac, Susan-Diana; Stockman, Robert A. & Howdle, Steven M. [Vis alle 7 forfattere av denne artikkelen] (2022). Comparative hydrodynamic characterisation of two hydroxylated polymers based on α-pinene- or oleic acid-derived monomers for potential use as archaeological consolidants. Scientific Reports. 12(1). doi: 10.1038/s41598-022-21027-4. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The Oseberg Viking ship burial is one of the most extensive collections of Viking wooden artefacts ever excavated in Norway. In the early twentieth century, many of these artefacts were treated with alum in order to preserve them, inadvertently leading to their current degraded state. It is therefore crucial to develop new bioinspired polymers which could be used to conserve these artefacts and prevent further disintegration. Two hydroxylated polymers were synthesised (TPA6 and TPA7), using α-pinene- and oleic acid-derived monomers functionalised with an acrylate moiety. Characterisation using biomolecular hydrodynamics (analytical ultracentrifugation and high precision viscometry) has shown that these polymers have properties which would potentially make them good wood consolidants. Conformation analyses with the viscosity increment (ν) universal hydrodynamic parameter and ELLIPS1 software showed that both polymers had extended conformations, facilitating in situ networking when applied to wood. SEDFIT-MSTAR analyses of sedimentation equilibrium data indicates a weight average molar mass M w of (3.9 ± 0.8) kDa and (4.2 ± 0.2) kDa for TPA6 and TPA7 respectively. Analyses with SEDFIT (sedimentation velocity) and MultiSig however revealed that TPA7 had a much greater homogeneity and a lower proportion of aggregation. These studies suggest that both these polymers—particularly TPA7—have characteristics suitable for wood consolidation, such as an optimal molar mass, conformation and a hydroxylated nature, making them interesting leads for further research.

• Cutajar, Michelle; Stockman, Robert A.; Braovac, Susan-Diana; Steindal, Calin Constantin; Zisi, Angeliki & Harding, Stephen Ernest (2022). Comparative Hydrodynamic Study on Non-Aqueous Soluble Archaeological Wood Consolidants: Butvar B-98 and PDMS-OH Siloxanes. Molecules. ISSN 1431-5157. 27(7). doi: 10.3390/molecules27072133. Fulltekst i vitenarkiv Vis sammendrag

  Butvar B-98 and PDMS-OH both have a demonstrable ability as consolidants for archaeological wood. This makes them both potential treatment options for the Oseberg collection, which is one of the most important archaeological finds from the Viking era. Both Butvar B-98 and PDMS-OH are soluble in organic solvents, offering a useful alternative to aqueous-based consolidants. Extensive characterisation studies were carried out on both of these polymers, with the use of analytical ultracentrifugation and viscometry, for the benefit of conservators wanting to know more about the physical properties of these materials. Short column sedimentation equilibrium analysis using SEDFIT-MSTAR revealed a weight-average molar mass (weight-average molecular weight) Mw of (54.0 ± 1.5) kDa (kg · mol−1) for Butvar B-98, while four samples of PDMS-OH siloxanes (each with a different molar mass) had an Mw of (52.5 ± 3.0) kDa, (38.8 ± 1.5) kDa, (6.2 ± 0.7) kDa and (1.6 ± 0.1) kDa. Sedimentation velocity confirmed that all polymers were heterogeneous, with a wide range of molar masses. All molecular species showed considerable conformational asymmetry from measurements of intrinsic viscosity, which would facilitate networking interactions as consolidants. It is anticipated that the accumulated data on these two consolidants will enable conservators to make a more informed decision when it comes to choosing which treatment to administer to archaeological artefacts.

• Lucejko, Jeannette Jacqueline; McQueen, Caitlin; Sahlstedt, Malin; Modugno, Francesca; Colombini, Maria Perla & Braovac, Susan (2021). Comparative chemical investigations of alum treated archaeological wood from various museum collections. Heritage Science. 9(1), s. 69–69. doi: 10.1186/s40494-021-00517-0. Fulltekst i vitenarkiv Vis sammendrag

  From the mid-1800s to the late 1960s, conservation by alum salts (KAl(SO4)2·12H2O—potassium aluminium sulphate), using various recipes, was a common method to prevent shrinkage and to strengthen waterlogged archaeological wooden objects. This method was mainly used in Scandinavia. The alum method appears to have also been applied to highly degraded archaeological waterlogged wood in other countries, for example in the U.S and Germany. Today, many of the archaeological wooden objects treated with alum show extreme deterioration and very low pH, which are attributed to the effects of the alum-treatment. This study investigated the extent of the current levels of chemical degradation in wooden objects conserved with alum salts at different points in time (1880s, 1930s and 1905–13) in order to understand their current condition and whether extent of degradation was in any way related to time of treatment, in an attempt to understand the rate of degradation. It was also an opportunity to compare the chemical state of preservation of alum-treated wood from different collections, as only the Oseberg collection has been intensively studied in this way up until now. Samples from historical wooden objects from the following collections were investigated and compared: the Dejbjerg collection (National Museum of Denmark in Copenhagen); the Oseberg collection (Museum of Cultural History, Oslo, Norway); the Glimmingehus collection (Swedish History Museum, Sweden). Analyses of lignocellulosic polymers and of inorganic compounds were undertaken to evaluate the chemical preservation of the wooden objects. The investigations were performed using a multi-analytical approach which consisted of: pH measurements, analytical pyrolysis (Py-GC/MS), X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS). It was possible to link the extent of degradation with time, on a general level but we found a great variability in the state of preservation of the wood also within the same collection. It is clear, however that alum-treated wood is more degraded than archaeological wood not treated with alum.

• Lucejko, Jeannette Jacqueline; LaMotte, Anne de; Andriulo, Fabrizio; Kutzke, Hartmut; Harding, Stephen Ernest & Phillips-Jones, Mary K [Vis alle 10 forfattere av denne artikkelen] (2021). Evaluation of Soda Lignin from Wheat Straw/Sarkanda Grass as a Potential Future Consolidant for Archaeological Wood. Forests. 12(7). doi: 10.3390/f12070911. Fulltekst i vitenarkiv Vis sammendrag

  This work is part of a larger study, which aims to use soda lignin from straw as the starting point for a non-aqueous consolidant for highly degraded archaeological wood from the Oseberg collection. This wood was treated with alum salts in the early 1900s, is actively degrading and exists in varying states of preservation. Non-aqueous consolidants are an option to stabilize this wood mechanically in cases where it is too deteriorated to undergo aqueous-based retreatments, for example using polyethylene glycol. The aim of this study was to compare the extent of penetration of two soda lignin preparations in low- to medium-degraded archaeological pine. The soda lignins were dissolved in ethyl acetate and had two molecular weight groups: P1000 (molecular weight Mw of~3 kDa) and the ethyl acetate fraction FB01 (Mw of ~1 kDa). Penetration after immersion was evaluated by infrared spectroscopy and analytical pyrolysis. Treated specimens were also evaluated using weight and dimensional change and scanning electron microscopy. Both lignins penetrated into sample cores, but P1000 did not penetrate as well as FB01. This may be due to differences in their molecular weights, but also differences in polarity due to the presence of different functional groups.

• Wakefield, Jennifer M.K.; Braovac, Susan-Diana; Kutzke, Hartmut; Stockman, Robert A. & Harding, Stephen Ernest (2020). Tert-butyldimethylsilyl chitosan synthesis and characterization by analytical ultracentrifugation, for archaeological wood conservation. European Biophysics Journal. ISSN 0175-7571. 49, s. 781–791. doi: 10.1007/s00249-020-01450-z. Fulltekst i vitenarkiv
• McQueen, Caitlin; Mortensen, Martin Nordvig; Caruso, Francesco; Mantellato, Sara & Braovac, Susan (2020). Oxidative degradation of archaeological wood and the effect of alum, iron and calcium salts. Heritage Science. 8(1). doi: 10.1186/s40494-020-00377-0. Fulltekst i vitenarkiv Vis sammendrag

  Oxygen consumption measurement was used to study potential oxidative degradation reactions occurring in wooden artefacts from the Viking age Oseberg collection in Norway. Model samples of fresh birch were impregnated with iron, calcium and alum salts to mimic concentrations of such compounds found in Oseberg artefacts and to assess their effect on oxygen consumption rates. The results showed that heated impregnation with alum salt (KAl(SO4)2·12H2O) significantly increased the rate of oxygen consumption, confirming a previously observed link between alum-treatment and wood oxidation. The presence of iron salts in alum-treated wood specimens, even at low concentrations, also substantially increased the oxidation rate. However, the mechanism by which this occurred appeared to be influenced by the alum-treatment. Samples treated with both iron and calcium salts were also studied, in order to investigate a proposed inhibition of iron-induced oxidation by calcium ions. However, these did not appear to consume oxygen at significantly different rates. In Oseberg samples, a large variation in oxygen consumption rates from 0.48 to an apparent 8.2 μg O2 (g wood)−1 day−1 was observed, and these values were consistently higher than those for reference fresh wood. The results demonstrated that oxygen consumption measurement is a viable method of evaluating chemical stability in this case, but is best applied to model samples with limited compositional variability.

• Braovac, Susan (2019). Practical experiences with cross-disciplinary research - the case of Saving Oseberg. Primitive tider. ISSN 1501-0430. 21, s. 143–148. Fulltekst i vitenarkiv
• McQueen, Caitlin; Lucejko, Jeannette J.; Flåte, Ingrid; Modugno, Francesca & Braovac, Susan (2019). Ammonium alum in alum-treated wooden artefacts: discovery, origins and consequences. Heritage Science. 7(1), s. 1–11. doi: 10.1186/s40494-019-0321-7. Fulltekst i vitenarkiv Vis sammendrag

  Alum-treatment was extensively applied to archaeological wood from the Oseberg collection in the early 1900s, and was a common conservation method at the time involving impregnating objects with hot concentrated solutions of potassium alum (KAl(SO4)2⋅12H2O). This now obsolete consolidation method has led to dramatic long-term consequences, heavily affecting the state of preservation of the historical wooden artefacts, and dedicated chemical characterisation campaigns have been undertaken to better understand the degradation processes and aid development of re-treatment strategies. Analyses with Fourier transform infrared spectroscopy (FTIR), elemental microanalysis, and ion chromatography (IC) was performed, suggesting the presence of ammonium alum (NH4Al(SO4)2·12H2O) in many alum-treated wood samples, though no record exists of use of ammonium compounds during treatment of the artefacts. C/N rations of 1.70–68.8 in wood samples, and ammonium alum contents between 8 and 84% of the alum component and 23–168 mmol/100 g of total sample suggested that objects were actually treated with various mixes of potassium and ammonium alum. The two alums have similar properties, and in model studies of their behaviour under the conditions of alum-treatment appeared to form similarly acidic solutions, thus the different alum mixtures probably did not significantly influence object treatment. Nor have we observed other indications of unusual degradation pathways related specifically to the presence of ammonium alum. Nonetheless, investigations into potential re-treatment of the archaeological objects must be adjusted accordingly.

• McQueen, Caitlin; Steindal, Calin Constantin; Narygina, Olga & Braovac, Susan (2018). Temperature- and humidity-induced changes in alum-treated wood: a qualitative X-ray diffraction study. Heritage Science. 6:66, s. 1–11. doi: 10.1186/s40494-018-0232-z. Fulltekst i vitenarkiv Vis sammendrag

  Alum-treated wooden artefacts suffer from extreme deterioration, and the stability of these objects and the salts they contain to variations in climate conditions is an important issue. Responses of potassium alum (KAl(SO4)2·12H2O), ammonium alum (NH4Al(SO4)2·12H2O), potassium bisulfate (KHSO4) and alum-treated wood to changing temperature and relative humidity (RH) were therefore investigated at the crystalline level using powder X-ray diffraction (XRD). The XRD analysis showed changes in the crystal structures of alum salts that suggest some degree of dehydration starting at 40 °C at 15% RH. Rehydration of such dehydrated alum in Oseberg wood samples was still ongoing after 2 years. However, alum salts on their own and in alum-treated wood generally appeared to be stable to most of the changing climate conditions. Conversely, the minor potassium bisulfate component found in some samples was very sensitive to all changes in RH and temperature, and may even cause changes to the alum component under some conditions. This may be related to the efflorescence of K9H7(SO4)8·H2O crystals seen on some fragments after long-term exposure to high RH. These findings can help to refine RH and temperature limits for alum-treated objects, and also demonstrate the utility of temperature- and RH-controlled XRD for qualitative monitoring of climate-induced changes in such salt-impregnated materials.

• Braovac, Susan; McQueen, Caitlin; Sahlstedt, Malin; Kutzke, Hartmut; Łucejko, Jeannette J. & Klokkernes, Torunn (2018). Navigating conservation strategies: linking material research on alum-treated wood from the Oseberg collection to conservation decisions. Heritage Science. 6:77, s. 1–16. doi: 10.1186/s40494-018-0241-y. Fulltekst i vitenarkiv Vis sammendrag

  From the mid-1800s to the late 1950s, conservation by alum salts (aluminum potassium sulfate dodecahydrate)—with some variations—was a routine method for treating highly deteriorated waterlogged archaeological wood in many countries, especially in Scandinavia. It was eventually replaced by newer methods in the 1960s, such as that using polyethylene glycol. Accordingly, the signs of deterioration in such collections and the reasons behind them are not well known among current preservation specialists. The research in the Saving Oseberg project (2014–2019) has shed light on the consequences of this treatment and reasons behind the severe deterioration observed today in many objects of the Oseberg Viking Age wooden finds, which were conserved in the early 1900s. Saving Oseberg aims to provide research-based recommendations for the future preservation of the finds, and as such, a large part of the project is aimed at improving our understanding of this complex material. Here the consequences of the method are summarized, drawing on the research to date. Chemical analyses of the Oseberg wood showed its current condition to be highly degraded: little polysaccharide content is left and the lignin is significantly oxidized and extensively depolymerized. The conservation implications are also discussed.

• McQueen, Caitlin; Tamburini, Diego & Braovac, Susan (2018). Identification of metal compounds in alum-treated wood from the Oseberg collection. I Williams, Emily & Hocker, Emma (Red.), Proceedings of the 13th ICOM-CC Group on Wet Organic Archaeological Materials Conference: Florence 2016. International Council of Museums Committee for Conservation (ICOM-CC). ISSN 9789290124368. s. 162–168. doi: 10.1038/s41598-018-21314-z. Fulltekst i vitenarkiv Vis sammendrag

  Wooden artefacts from the Oseberg collection contain various metal compounds arising from factors such as alum-treatment, the use of metal joiners and storage in metal tanks. Such compounds can significantly influence the condition of the wood, and therefore inorganic characterisation is important to include in studies of the wood. Using XRD, FTIR spectroscopy and SEM-EDS, we have been able to characterise metal compounds in several alum-treated wood fragments, including alum decomposition products, iron and zinc corrosion products and combinations thereof.

• McQueen, Caitlin; Tamburini, Diego & Braovac, Susan (2018). Identification of inorganic compounds in composite alum-treated wooden artefacts from the Oseberg collection. Scientific Reports. 8. doi: 10.1038/s41598-018-21314-z. Fulltekst i vitenarkiv Vis sammendrag

  Alum-treated wooden artefacts from the Oseberg collection display a great deal of morphological, structural and compositional inhomogeneity. Thus, an in-depth understanding of chemical processes underlying their degradation requires consideration of a variety of local environments. In addition to alum, sources of inorganic compounds include metal parts, corrosion products of which can migrate into the surrounding wood. In order to characterise the inorganic compounds a range of local environments, samples from several locations in a selection of composite objects have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS). We have found that corrosion of iron rods used in reconstruction has formed iron(II) sulfates, which have migrated into the alum-treated wood to form sulfates containing combinations of potassium, aluminium, iron(II) and iron(III) cations. Reactions of alum were also evident from the presence of alunite in some samples. Areas with significant abundances of zinc sulfates, zinc sulfide and elemental sulfur were also detected. These results provide a first-time window into the complex array of inorganic species that can be present in such composite alum-treated objects.

• Andriulo, Fabrizio; Giorgi, Rodorico; Steindal, Calin Constantin; Kutzke, Hartmut & Braovac, Susan (2018). Nanotechnologies for the restoration of alum-treated archaeological wood. I Williams, Emily & Hocker, Emma (Red.), Proceedings of the 13th ICOM-CC Group on Wet Organic Archaeological Materials Conference: Florence 2016. International Council of Museums Committee for Conservation (ICOM-CC). ISSN 9789290124368. s. 176–183. doi: 10.1007/s00339-016-9833-0. Fulltekst i vitenarkiv
• Dionisi-Vici, P; Braovac, Susan; Hauer, David & Jensen, Maria Malherbes (2018). Measuring stress levels of archaeological samples from the Oseberg ship under fluctuating relative humidity - preliminary results. I Williams, Emily & Hocker, Emma (Red.), Proceedings of the 13th ICOM-CC Group on Wet Organic Archaeological Materials Conference: Florence 2016. International Council of Museums Committee for Conservation (ICOM-CC). ISSN 9789290124368. s. 333–337. Fulltekst i vitenarkiv Vis sammendrag

  Long-term effects of climate fluctuations are very important to consider regarding preservation of archaeological wooden artifacts. Since 2009, a hygromechanical monitoring has been carried out on the Oseberg ship in the Viking Ship Museum (VSH) in Oslo. The monitoring has showed a measurable warping response of the oak planks to the uncontrolled relative humidity fluctuations in the museum. However, one of the missing pieces of information for an improved understanding of the hygro-mechanical behavior of the ship is the measurement of the stress levels potentially absorbed by the restrained planks during relative humidity (RH) fluctuations. Here, a methodology aiming to contribute to this analysis is proposed and the first results of the tests are presented. Measurements were carried out in a climate chamber, simulating the average extremes in RH commonly measured at VSH (30% and 75% RH). The experimental results will allow us to determine realistic climatic set points for the plans of a new museum complex.

• McHale, Emily; Braovac, Susan; Steindal, Calin Constantin; Kutzke, Hartmut & Benneche, Tore (2018). Consolidation of waterlogged wood with lignin-like oligomers. I Williams, Emily & Hocker, Emma (Red.), Proceedings of the 13th ICOM-CC Group on Wet Organic Archaeological Materials Conference: Florence 2016. International Council of Museums Committee for Conservation (ICOM-CC). ISSN 9789290124368. s. 184–192. doi: 10.1038/srep46481. Fulltekst i vitenarkiv
• Emanuelsson, Emma & Braovac, Susan (2018). Re-conservation of glycerol-conserved ropes from the Viking Age Oseberg ship. I Williams, Emily & Hocker, Emma (Red.), Proceedings of the 13th ICOM-CC Group on Wet Organic Archaeological Materials Conference: Florence 2016. International Council of Museums Committee for Conservation (ICOM-CC). ISSN 9789290124368. s. 379–382. Fulltekst i vitenarkiv
• Lucejko, Jeannette J.; Nasa, Jacopo La; McQueen, Caitlin; Braovac, Susan; Colombini, Maria Perla & Modugno, Francesca (2018). Protective effect of linseed oil varnish on archaeological wood treated with alum. Microchemical Journal. ISSN 0026-265X. 139, s. 50–61. doi: 10.1016/j.microc.2018.02.011. Fulltekst i vitenarkiv Vis sammendrag

  The Viking Age wooden artefacts recovered in the early 1900s from the Oseberg mound (Norway) and treated with alum, are today highly degraded. This is due to the effects of the alum-treatment and the reactivity of alum and alum-derived salts [1]. Some of the artefacts from the Oseberg collection that were treated with alum were also coated with a drying oil: boiled linseed oil. These artefacts appear to be better preserved with respect to those not treated with linseed oil. In order to assess the effect of linseed oil on wood preservation, an alum-treated archaeological wood fragment from the Oseberg collection treated with linseed oil was investigated by three analytical techniques: gas chromatography coupled with mass spectrometry (GC/MS), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and high-performance liquid chromatography coupled to electrospray ionisation and quadrupole time-of-flight mass spectrometry (HPLC-ESI-Q-ToF). These techniques provided important information on the molecular composition and state of preservation of both archaeological wood and aged linseed oil. Py(HMDS)-GC/MS was applied to assess the state of preservation of the main wood components, lignin and polysaccharides, in the presence of linseed oil and alum treatments. GC/MS and HPLC-ESI-Q-ToF were used to perform lipid characterisation and to investigate the lipid degradation and oxidation processes. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and elemental analysis by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) were performed to give information on the corresponding inorganic components, particularly the composition and distribution of the alum. Samples taken at different depths from the surface of the archaeological wood fragment were analysed and compared. The results showed that, although the wood was highly depleted of carbohydrates, it was better preserved than previously analysed Oseberg artefacts not treated with linseed oil. Results from GC/MS and HPLC-ESI-Q-ToF suggested that the linseed oil played a mitigating role in terms of wood degradation. The behaviour of the lipid material, which was more oxidized on the wood surface than in the core, was the opposite to that usually encountered in archaeological wood, suggesting a selective oxidation of the linseed oil. This unusual pattern of wood degradation was not mirrored by the inorganic components: alum was found to be more abundant at the surface of the fragment than at depth, as would be expected, but no decomposition products were found. However, the alum appeared to mainly consist of ammonium salt, rather than the potassium alum documented as the treatment material for the Oseberg artefacts.

• McQueen, Caitlin; Tamburini, Diego; Łucejko, Jeannette Jacqueline; Braovac, Susan; Gambineri, Francesca & Modugno, Francesca [Vis alle 8 forfattere av denne artikkelen] (2017). New insights into the degradation processes and influence of the conservation treatment in alum-treated wood from the Oseberg collection. Microchemical Journal. ISSN 0026-265X. 132, s. 119–129. doi: 10.1016/j.microc.2017.01.010. Fulltekst i vitenarkiv Vis sammendrag

  The Oseberg collection includes the most complete ensemble of wooden remains from the Viking Age. However, since many of the wooden objects were treated with alum in the early 1900s, they now suffer from dramatic conservation issues. A multi-analytical approach was adopted to investigate both the organic and the inorganic components of some selected wood fragments, with the aim of fully characterising the materials and their decomposition products. A particular focus was taken on the differences between the surface and the core of the fragments analysed, and on the correlations between the results obtained by the different techniques, in order to disclose possible interactions between the materials during degradation. In addition to differences in alum concentration and wood alteration between the surface and the core, some decomposition/transformation products of alum, such as mercallite (KHSO4), were identified by FTIR and XRD. Contextual interpretation of the results obtained by ICP-OES elemental analysis of inorganic components and Py(HMDS)-GC/MS characterisation of degraded lignocellulosic materials supported some previous observations about potential relationships between specific metals (Al, Fe, Ca) and wood degradation and enabled new correlations to be highlighted. Although similar degradation patterns were revealed in the investigated objects–depletion of holocellulose, oxidation of lignin and some transformation of alum - a notable variability at the molecular level was highlighted. This is an important factor to be taken into account for the planning of re-treatment strategies of these extremely precious artefacts.

• Andriulo, Fabrizio; Giorgi, Rodorico; Baglioni, Piero; Steindal, Calin Constantin; Braovac, Susan & Kutzke, Hartmut (2017). Hybrid nanocomposites made of diol-modified silanes and nanostructured calcium hydroxide. Applications to Alum-treated wood. Pure and Applied Chemistry. ISSN 0033-4545. doi: 10.1515/pac-2016-1014. Fulltekst i vitenarkiv
• Andriulo, Fabrizio; Giorgi, Rodorico; Steindal, Calin Constantin; Kutzke, Hartmut; Baglioni, Piero & Braovac, Susan (2017). Hybrid nanocomposites made of diol-modified silanes and nanostructured calcium hydroxide. Applications to Alum-treated wood. Pure and Applied Chemistry. ISSN 0033-4545. doi: 10.1515/pac-2016-1014. Fulltekst i vitenarkiv
• Andriulo, Fabrizio; Braovac, Susan; Kutzke, Hartmut; Giorgi, Rodorico & Baglioni, Piero (2016). Nanotechnologies for the restoration of alum-treated archaeological wood. Applied Physics A: Materials Science & Processing. ISSN 0947-8396. Fulltekst i vitenarkiv
• McHale, Emily; Braovac, Susan; Steindal, Calin Constantin; Gillis, Richard B; Adams, Gary & Harding, Stephen E [Vis alle 8 forfattere av denne artikkelen] (2016). Synthesis and characterisation of lignin-like oligomers as a bio-inspired consolidant for waterlogged archaeological wood. Pure and Applied Chemistry. ISSN 0033-4545. 88(10-11), s. 969–977. doi: 10.1515/pac-2016-0814. Fulltekst i vitenarkiv Vis sammendrag

  The development of new materials for the consolidation of waterlogged archaeological wood from sustainable sources is an important area of research, as the most widely used consolidant today is petroleum based. Ideally a new consolidant will interact with the existing wood structure, ensuring maximum compatibility. Lignin is often the major component remaining in archaeological wood, as it is less susceptible to degradation than holocellulose. Therefore, in order to maximise the potential for interaction with the wood cells, lignin-like oligomers have been synthesized from isoeugenol using a water soluble copper salen catalyst at pH 10, giving a weight average Mw of 1.6 kDa. Analysis by NMR spectroscopy has shown that the oligomers have a lignin-like structure with β-O-4′, β-β′ and β-5′ connections. A 10 w/w% solution of the oligomers in ethyl acetate was found to thoroughly penetrate 1 cm3 samples of waterlogged archaeological wood (density of 0.146 g/mL, maximum water content of 620%) after 14 days impregnation, as determined by FTIR spectroscopy. No impregnation material could be seen by SEM, suggesting that it coats the cell walls upon drying. This indicates that dehydrogenated polymers penetrate waterlogged archaeological wood well and have the potential to be developed into consolidants.

• Braovac, Susan; Tamburini, Diego; Łucejko, Jeannette Jacqueline; McQueen, Caitlin; Kutzke, Hartmut & Colombini, Maria Perla (2016). Chemical analyses of extremely degraded wood using analytical pyrolysis and inductively coupled plasma atomic emission spectroscopy. Microchemical Journal. ISSN 0026-265X. 124, s. 368–379. doi: 10.1016/j.microc.2015.09.016. Fulltekst i vitenarkiv
• Andriulo, Fabrizio; Braovac, Susan; Kutzke, Hartmut; Giorgi, Rodorico & Baglioni, Piero (2016). Nanotechnologies for the restoration of alum-treated archaeological wood. Applied Physics A: Materials Science & Processing. ISSN 0947-8396. 122(4). doi: 10.1007/s00339-016-9833-0. Fulltekst i vitenarkiv
• Bader, Thomas; Borst, Karin de; Fackler, Karin; Ters, Thomas & Braovac, Susan (2013). A nano to macroscale study on structure-mechanics relationships of archaeological oak. Journal of Cultural Heritage. ISSN 1296-2074. 14(5), s. 377–388. doi: 10.1016/j.culher.2012.09.007. Fulltekst i vitenarkiv
• Kutzke, Hartmut & Braovac, Susan (2013). Conservation of archaeological wood: the Oseberg find. I Rennie, John; Weil, Jonathan; Blumel, David; Malmoli, Stefan & Maybaum, Hilary (Red.), Yearbook of Science and Technology 2013. McGraw-Hill. ISSN 9780071801409. s. 89–92. Fulltekst i vitenarkiv
• Braovac, Susan; Hjulstad, Guro & Storbekk, Elin Christine (2012). Decisions about moving collections – where do conservators fit in? How can we contribute? I Bronken, Ida Antonia Tank; Braovac, Susan; Olstad, Tone Marie & Ørnhøi, Anne Apalnes (Red.), Moving Collections. Processes and Consequences. Archetype Publications Ltd.. ISSN 9781904982845. s. 175–184. Fulltekst i vitenarkiv
• Braovac, Susan & Kutzke, Hartmut (2012). The presence of sulfuric acid in alum-conserved wood – origin and consequences. Journal of Cultural Heritage. ISSN 1296-2074. 13(3), s. 203–208. doi: 10.1016/j.culher.2012.02.002. Fulltekst i vitenarkiv
• Braovac, Susan (2002). Samlingene på Vikingskipshuset: tilstand og vurdering. Skrifter - Universitetet i Oslos kulturhistoriske museer. ISSN 1503-0792. 1, s. 31–40. Fulltekst i vitenarkiv

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• Bronken, Ida Antonia Tank; Braovac, Susan; Olstad, Tone Marie & Ørnhøi, Anne Apalnes (2012). Moving Collections. Processes and Consequences. Archetype Publications Ltd.. ISBN 9781904982845. 220 s. Fulltekst i vitenarkiv
• Braovac, Susan; Bader, Thomas; Fackler, Karin & Hofstetter, Karin (2011). Stiffness properties of the archaeological oak wood from the Oseberg ship. Fraunhofer IRB Verlag. ISBN 9783816785606. 310 s. Fulltekst i vitenarkiv
• Braovac, Susan; Fackler, Karin; Ters, Thomas & Bader, Thomas (2011). Chemical composition of the archaeological oak wood from the Oseberg ship. Fraunhofer IRB Verlag. ISBN 9783816785606. 310 s. Fulltekst i vitenarkiv

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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. Fulltekst i vitenarkiv Vis sammendrag

  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

• Braovac, Susan & Viestad, Vibeke Maria (2020). Arkeologi på rappen 3-4: Susan Braovac on Saving Oseberg and cross-disciplinary research (podcast). [Radio]. Primitive tider Arkeologi på rappen 3-4. Fulltekst i vitenarkiv
• Braovac, Susan & Andriulo, Fabrizio (2020). Applying alkaline nanoparticles to deacidify alum-treated wood. Fulltekst i vitenarkiv
• Wakefield, Jennifer M.K.; Steindal, Calin Constantin; Piva, Eleonora; Stockman, R; Adams, Gary & Heinze, T [Vis alle 8 forfattere av denne artikkelen] (2019). Investigation of natural polymers for treatments of Oseberg artifacts-review of lab degraded and archaeological wood. Fulltekst i vitenarkiv
• Braovac, Susan; Sahlstedt, Malin & Wittköpper, Markus (2019). Retreatment testing of alum-treated woods from the Oseberg collection – results from first trials. Fulltekst i vitenarkiv
• McQueen, Caitlin; Braovac, Susan; Lucejko, Jeannette J. & Modugno, F (2019). Unexpected ammonium compounds in alum-treated wood from the Oseberg collection. Fulltekst i vitenarkiv
• Lucejko, Jeannette J.; McQueen, Caitlin; Braovac, Susan; Sahlstedt, Malin; Modugno, F & Caruso, Francesco [Vis alle 8 forfattere av denne artikkelen] (2019). Acid-catalyzed hydrolysis of paper in contact with acidic wood. Fulltekst i vitenarkiv
• Lucejko, Jeannette J.; Sahlstedt, Malin; McQueen, Caitlin; Modugno, F & Braovac, Susan (2019). Comparative chemical investigations of alum treated archaeological wood from different museum collections. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• McQueen, Caitlin; Tamburini, Diego & Braovac, Susan (2017). FTIR microscopy for analysis of treated archaeological wood samples. Fulltekst i vitenarkiv
• McQueen, Caitlin; Kutzke, Hartmut & Braovac, Susan (2016). Identification of metal compounds in alum-treated wood from the Oseberg collection. Fulltekst i vitenarkiv
• McHale, Emily; Steindal, Calin Constantin; Braovac, Susan; Gillis, Richard; Adams, Gary & Benneche, Tore [Vis alle 7 forfattere av denne artikkelen] (2016). Synthesis and characterisation of lignin-like oligomers as a bio-inspired consolidant for waterlogged archaeological wood. Fulltekst i vitenarkiv
• Andriulo, Fabrizio; Giorgi, Rodorico; Steindal, Calin Constantin; Kutzke, Hartmut; Braovac, Susan & Baglioni, Piero (2016). Nanotechnologies for the restoration of alum-treated archaeological wood. Fulltekst i vitenarkiv
• McHale, Emily; Braovac, Susan; Steindal, Calin Constantin; Kutzke, Hartmut & Benneche, Tore (2016). Consolidation of waterlogged archaeological wood with lignin-like oligomers. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Braovac, Susan; Hauer, David; Steindal, Calin Constantin; McQueen, Caitlin; Andriulo, Fabrizio & McHale, Emily (2016). Oseberg-konserveringen for dummies. Museumsnytt. ISSN 0027-4186. Fulltekst i vitenarkiv
• Tamburini, Diego; Lucejko, Jeannette J.; Modugno, Francesca; Colombini, Maria Perla; Kutzke, Hartmut & Braovac, Susan [Vis alle 9 forfattere av denne artikkelen] (2015). The ArCo Project - Ageing Studies of Treated Composite Archaeological Waterlogged Artefacts - preliminary results. Fulltekst i vitenarkiv
• Tamburini, Diego; Braovac, Susan; Lucejko, Jeannette J.; Modugno, Francesca; McQueen, Caitlin & Kutzke, Hartmut [Vis alle 7 forfattere av denne artikkelen] (2015). Chemical analysis of degraded wood by Py-GC/MS and ICP-AES. Fulltekst i vitenarkiv
• Tamburini, Diego; Lucejko, Jeannette J.; Modugno, Francesca; Colombini, Maria P.; Kutzke, Hartmut & Braovac, Susan [Vis alle 9 forfattere av denne artikkelen] (2015). PY-GC-MS with in situ silylation to the analysis of treated composite archaeological wood artifacts - the ArCo project. Fulltekst i vitenarkiv
• Hauer, David; Andriulo, Fabrizio; McQueen, Caitlin; Braovac, Susan; Steindal, Calin Constantin & Kutzke, Hartmut [Vis alle 7 forfattere av denne artikkelen] (2015). Håper at vikingskattene kan reddes. [TV]. NRK Dagsrevuen. Fulltekst i vitenarkiv
• McQueen, Caitlin; Kutzke, Hartmut & Braovac, Susan (2015). Metal ions in archaeological wood from the Oseberg find – a complex issue? Fulltekst i vitenarkiv
• McHale, Emily; Benneche, Tore; Kutzke, Hartmut; Christensen, Mikkel & Braovac, Susan (2014). Preservation of archaeological wood: a challenge for biomimetic materials. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Braovac, Susan; Bill, Jan & Løchen, Ragnar (2013). Åndenes Makt. [TV]. TVNorge. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Kutzke, Hartmut; Christensen, Mikkel & Braovac, Susan (2012). Hvor fortid og fremtid møtes - med forskerlupe i Osebergfunnet. Fulltekst i vitenarkiv
• Kutzke, Hartmut; Braovac, Susan; Christensen, Mikkel & Gjengedal, Kjerstin (2012). Nasjonalskatt går i oppløysing. [Journal]. Apollon. Fulltekst i vitenarkiv
• Kutzke, Hartmut; Braovac, Susan & Euler, Harald (2011). The behaviour of alum in alum-conserved wooden objects. Fulltekst i vitenarkiv
• Braovac, Susan; Jensen, Maria; Aarseth, Bjarte Einar; Bill, Jan; Hjulstad, Guro & Løchen, Ragnar [Vis alle 9 forfattere av denne artikkelen] (2011). Long term responses in archaeological wood to ambient temperature and relative humidity – case study: the Oseberg Ship. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Lehmann, Eberhard; Mannes, David; Hunger, K.; Wörle, Marie; Braovac, Susan & Kutzke, Hartmut [Vis alle 7 forfattere av denne artikkelen] (2011). Wood investigations by means of radiation transmission techniques in the analysis of cultural heritage objects of different size scale. Fulltekst i vitenarkiv
• Kutzke, Hartmut; Braovac, Susan; Christensen, Mikkel & Hansen, Finn Knut (2011). Old treatments – new solutions? Summary of activities of the Alum Research Group. Fulltekst i vitenarkiv
• Bisulca, Christina; Odegaard, Nancy; Braovac, Susan & Kutzke, Hartmut (2011). Consolidation of Alum-Treated Wood with Alkoxysilanes. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv Vis sammendrag

  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.

• Kutzke, Hartmut; Braovac, Susan & Christensen, Mikkel (2011). Kunsten å bevare vikingkunst - ingen enkel kunst. Preserving the objects from Oseberg. Fulltekst i vitenarkiv
• Braovac, Susan & Kutzke, Hartmut (2010). Past Conservation Treatments and their Consequences – the Oseberg Find as a case study. Fulltekst i vitenarkiv
• Braovac, Susan; Christensen, Mikkel; Kutzke, Hartmut; Hartmann, Stefan; Mokso, Raimund & Lehmann, Eberhard (2010). Looking inside! 3D imaging experiments on alum-conserved archaeological wood. Fulltekst i vitenarkiv
• Braovac, Susan; Christensen, Mikkel; Kutzke, Hartmut; Hartmann, Stefan; Mokso, Rajmund & Lehmann, Eberhard (2010). Looking inside! 3D imaging experiments on alum-conserved archaeological wood. Fulltekst i vitenarkiv
• Christensen, Iben V.; Ottosen, Lisbeth M.; Jensen, Poul; Bojesen-Koefoed, Inger; Kutzke, Hartmut & Braovac, Susan [Vis alle 8 forfattere av denne artikkelen] (2010). The use of an electric field for the removal of alum from treated wooden objects. Fulltekst i vitenarkiv
• Kutzke, Hartmut; Braovac, Susan & Christensen, Mikkel (2009). Historische Konservierungsmethoden als neue Herausforderung fuer die Archaeometrie: Die alaunbehandelten Holzobjekte des Osebergfundes. Fulltekst i vitenarkiv
• Braovac, Susan & Kutzke, Hartmut (2009). The Presence of Sulfuric Acid in Alum-conserved Wood – Origin and Consequences. Fulltekst i vitenarkiv
• Vici, Paolo Dionisi; Aarseth, Bjarte Einar; Bill, Jan; Hjulstad, Guro; Jensen, Maria Malherbes & Løchen, Ragnar [Vis alle 9 forfattere av denne artikkelen] (2009). In-situ deformation measurements on a large wooden archaeological artefact: the Viking Age Oseberg ship. Fulltekst i vitenarkiv
• Christensen, Iben V.; Ottosen, Lisbeth M.; Jensen, Poul; Bojesen-Koefoed, Inger; Kutzke, Hartmut & Braovac, Susan [Vis alle 8 forfattere av denne artikkelen] (2009). The use of an electric field for the removal of alum from treated wooden objects. Fulltekst i vitenarkiv
• Braovac, Susan (2008). Rescuing the Oseberg Find, a Project in Progress. Alum-conserved Wood - Mechanisms of Deterioration and Development of Preservation Strategies. Fulltekst i vitenarkiv
• Braovac, Susan (2008). History of the Viking ship collections and their conservation challenges. Fulltekst i vitenarkiv
• Braovac, Susan (2007). The Viking Ship finds: Preservation Challenges and the search for potential solutions. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Vedeler, Marianne & Braovac, Susan (2003). Nytt liv i gamle magasiner. Museumsnytt. ISSN 0027-4186. 52(3). Fulltekst i vitenarkiv

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