Evaluation of Soda Lignin from Wheat Straw/Sarkanda Grass as a Potential Future Consolidant for Archaeological Wood

Abstract

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.

Evaluation of two terpene-derived polymers as consolidants for archaeological wood

“…Wood with a high degree of degradation has a density of ~ 0.1 g/mL while sound wood usually has a density of ~ 0.4-0.5 g/mL 11 . Well-preserved pine speci cally is reported to have a density of around 0.5 g/mL 3 . With regards to MMC, a value of above 400% indicates that the wood is highly degraded 14 .…”

“…These solutions were then used to soak the assigned wood specimens. Control group 2, as well as both treatment groups were left immersed in their respective solutions for two weeks, based on a previous report of wood testing with non-aqueous treatments 3 . The wood cubes were then removed from the solutions and left to slowly air-dry in a fume-hood for one week, after which they were kept in climate chamber at 20°C and 50% RH.…”

“…The most popular conservation method usually involves treatment with polyethylene glycol (PEG) and subsequent freeze-drying. If the Oseberg artefacts are retreated using this method, they would rst have to be immersed in water, to remove the alum salts and acid, before adding PEG 3 . Retreating the Oseberg artefacts is not such a simple matter however, due to the large variation of the wood's preservation state.…”

“…A particular emphasis was put on the sustainability of the new materials, with the use of bioinspired polymers whenever possible. Examples of materials that have been investigated include lignin 3 , isoeugenol 4,5 , chitosan 6,7 and aminocellulose 8 . Most recently, we have developed polymers derived from terpenes with functionalised hydroxylated moieties 9,10 .…”

Evaluation of two terpene-derived polymers as consolidants for archaeological wood

“…The most popular conservation method usually involves treatment with polyethylene glycol (PEG) and subsequent freeze-drying 3 . If the Oseberg artefacts are retreated using this method, they would first have to be immersed in water, to remove the alum salts and acid, before adding PEG 4 . Retreating the Oseberg artefacts is not such a simple matter however, due to the large variation of the wood’s preservation state.…”