No abstract

There is currently a pressing need for the development of novel bioinspired consolidants for waterlogged, archaeological wood. Bioinspired materials possess many advantages, such as biocompatibility and sustainability, which makes them ideal to use in this capacity. Based on this, a polyhydroxylated monomer was synthesised from α-pinene, a sustainable terpene feedstock derived from pine trees, and used to prepare a low molar mass polymer TPA5 through free radical polymerisation. This polymer was extensively characterised by NMR spectroscopy (chemical composition) and molecular hydrodynamics, primarily using analytical ultracentrifugation reinforced by gel filtration chromatography and viscometry, in order to investigate whether it would be suitable for wood consolidation purposes. Sedimentation equilibrium indicated a weight average molar mass Mw of (4.3 ± 0.2) kDa, with minimal concentration dependence. Further analysis with MULTISIG revealed a broad distribution of molar masses and this heterogeneity was further confirmed by sedimentation velocity. Conformation analyses with the Perrin P and viscosity increment ν universal hydrodynamic parameters indicated that the polymer had an elongated shape, with both factors giving consistent results and a consensus axial ratio of ~ 4.5. These collective properties—hydrogen bonding potential enhanced by an elongated shape, together with a small injectable molar mass—suggest this polymer is worthy of further consideration as a potential consolidant.

This paper aims to expand our understanding of the processes involved in the production of the artificial pigment Egyptian blue through the scientific examination of pigments found in the first century BCE workshop of the Greek island of Kos. There, 136 Egyptian blue pellets were brought to light, including successfully produced pellets, as well as partially successful and unsuccessful products. This study is based on the examination of eighteen samples obtained from pellets of various textures and tones of blue, including light and dark blue pigments, coarse and fine-grained materials, and one unsuccessful pellet of dark green/grey colour. The samples were examined by optical microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and micro-Raman spectroscopy. These complementary microanalytical techniques provide localised information about the chemical and mineralogical composition of this multicomponent material, at a single-grain level. The results shed light on the firing procedure and indicate possible sources for raw materials (beach sand, copper alloys), as well as demonstrating the use of a low-alkali starting mixture. Moreover, two different process for the production of light blue pigments were identified: (a) decreased firing time and (b) grinding of the initially produced pellet and mixing with cobalt-containing material.

The project Saving Oseberg is funded by the Norwegian State with the aim to preserve the Viking Age wooden objects from the Oseberg burial mound. They were excavated in 1904 near Tønsberg, Norway, and many have been treated in the past with alum salts (KAl(SO 4 ) 2 Á12H 2 O). Alum was widely used during the early 1900s as a treatment for archaeological wood to prevent shrinkage and impart strength. In the 1990s, conservators observed an alarming condition of the objects. Initial investigations showed that the alum treatment has initiated a slow but ongoing deterioration process, attacking the wood for over 100 years. Today, the artefacts are highly acidic and have significantly reduced mechanical strength. In the last decade, the use of nonaqueous alkaline nanoparticle dispersions has provided successful results for the protection of cellulose-based materials. Alum-treated archaeological wood samples from Oseberg, with a pH B 2, have been treated with alkaline nanoparticle dispersions, and the effects of the treatment have been evaluated by thermal analysis (TG-DTG), infrared spectroscopy (ATR-FTIR) and X-ray microtomography (micro-CT) analyses. In this contribution, the preliminary results will be presented.

The presented research examines 17th century distemper paint from the polychrome wooden interiors of two Norwegian stave churches: Eidsborg and Heddal. For the first time, the inorganic and organic components of specimens from Eidsborg and Heddal were identified using X-ray Diffraction (XRD), Environmental Scanning Electron Microscopy (ESEM)—Energy Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared (FT-IR) spectroscopy, Enzyme-Linked Immunosorbent Assay (ELISA), and Gas Chromatography-Mass Spectrometry (GC-MS) after derivatization. This multi-analytical approach allowed for the identification of red ochre as the main red pigment within the topcoat (with the possible addition of minium), confirmed that a chalk basecoat was used, and finally permitted the recognition of alteration phases. Markers of proteinaceous material attributed to the use of animal-based glues were detected throughout the stratigraphic layers of both churches, with the addition of linseed oil in some locations. Furthermore, the wood substrate showed markers characteristic of pine tree, with contamination of wood fractions being detected in some of the paint samples from Heddal and Eidsborg. This research has contributed to a better understanding of the current preservation state of Heddal and Eidsborg, and ultimately assisted in developing a deeper comprehension and awareness of materials used in Norwegian stave churches.

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.

The alum-treated Viking Age archaeological wooden objects from the Oseberg find have undergone extensive chemical deterioration due to the original conservation treatment, based on alum salts (KAl(SO4)2·12H2O), done in the early 1900s. Today, the artifacts are highly acidic (pH≤2) and fragile; in some cases wood has almost completely lost its structural integrity. Research on conservation methods for these finds is currently underway. In the present study, organic/inorganic multi-functional ‘hybrid systems’ – using propylene glycol modified TEOS and alkaline nanoparticles (Ca(OH)2) – have been engineered to deacidify and consolidate alum-treated wood in a single step. The advantage of using silicon monomer and nano-materials as a starting point resides in their ease of penetration into the wood structure, where silicon monomers subsequently undergo polymerization. Treated samples were investigated using thermal analysis (DTG), X-Ray Diffraction (XRD), infrared spectroscopy (ATR-FTIR), SEM/EDX and Gas Chromatography Mass Spectroscopy (GC-MS). Results suggest that in addition to consolidating the wood, alkoxysilanes could act as a bridging agent between remaining lignin and calcium hydroxide nanoparticles.

Lignins are valuable renewable resources for the potential production of a large array of biofuels, aromatic chemicals and biopolymers. Yet native and industrial lignins are complex, highly branched and heterogenous macromolecules, properties that have to date often undermined their use as starting materials in lignin valorisation strategies. Reliable knowledge of weight average molar mass, conformation and polydispersity of lignin starting materials can be proven to be crucial to and improve the prospects for the success of such strategies. Here we evaluated the use of commonly-used size exclusion chromatography (SEC)—calibrated with polystyrene sulphonate standards—and under-used analytical ultracentrifugation—which does not require calibration—to characterise a series of lignin fractions sequentially extracted from soda and Kraft alkaline lignins using ethyl acetate, methyl ethyl ketone (MEK), methanol and acetone:water (fractions F01–F04, respectively). Absolute values of weight average molar mass (Mw) determined using sedimentation equilibrium in the analytical ultracentrifuge of (3.0 ± 0.1) kDa and (4.2 ± 0.2) kDa for soda and Kraft lignins respectively, agreed closely with previous SEC-determined Mws and reasonably with the size exclusion chromatography measurements employed here, confirming the appropriateness of the standards (with the possible exceptions of fraction F05 for soda P1000 and F03 for Indulin). Both methods revealed the presence of low (~ 1 kDa) Mw material in F01 and F02 fractions followed by progressively higher Mw in subsequent fractions. Compositional analysis confirmed > 90% (by weight) total lignins successively extracted from both lignins using MEK, methanol and acetone:water (F02 to F04). Considerable heterogeneity of both unfractionated and fractionated lignins was revealed through determinations of both sedimentation coefficient distributions and polydispersity indices. The study also demonstrates the advantages of using analytical ultracentrifugation, both alongside SEC as well as in its own right, for determining absolute Mw, heterogeneity and conformation information for characterising industrial lignins.