Evaluation of cell wall reinforcement in feather keratin-treated waterlogged wood as imaged by synchrotron X-ray microtomography (μXRT) and TEM

Abstract

Archaeological waterlogged woods (WLW) become considerably fragile over time because of chemical hydrolysis and the deterioration by microorganisms in the wet buried environment. The methods are sought for the dimensional stabilization of such woods. In the present article, the conservation of archaeological WLW of Chamaecyparis pisifera (Sieb. et Zucc.) Endl. by means of a commercially available feather keratin was in focus. The impregnation of an ancient wood from the 9th century A.D. was examined by the noninvasive synchrotron X-ray microtomography, which is well suited for imaging fragile samples. The thickness of the cell walls of keratin-treated wood was preserved and was comparable with that of recent wood. Notably, the middle lamella (ML) of keratin-treated wood appeared to be electron dense as indicated by transmission electron microscopy. Thus, it can be concluded that feather keratin is predominantly adsorbed on the ML and it prevents wood cell walls from collapsing and provides reinforcement.

Evaluation of chemical treatments on dimensional stabilization of archeological waterlogged hardwoods obtained from the Thang Long Imperial Citadel site, Vietnam

“…This phenomenon was also found in previous report [22]. This could be due to the interactions between degradation products of lignin in WW and keratin were not well established [18]. Within the WW species analyzed, PEG and trehalose treatment provided quite similar shrinkage values, while large variation of shrinkage rate was observed in keratin treatment.…”

“…The samples were immersed in distilled water under reduced pressure (0.1 MPa) for 40 min and the weight of each specimen was measured. The keratin treatment can reinforce the waterlogged softwoods as reported in the previous paper [18], while the effect was not enough to stabilize waterlogged hardwoods and other fragile materials [22]. The treatment was modified with adding a divalent metal salt process to integrate the keratin [26].…”

“…Interest in further seeking green materials (such as keratin [16][17][18][19]) for the consolidation of wood has been increasing in recent years [20,21]. The dimensional stability of the WW treated with keratin was excellent [17,18], except for the experiment on heavily degraded wood [22]. The treatment involving feather keratin enhanced the mechanical properties of WW [23].…”

Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties

“…A few examples may illustrate this: XCT was applied to study wood species (Trtik et al 2007; Van den Bulcke et al 2009;Svedström et al 2012), wood coatings (Van den Bessières et al 2013), structural changes during drying and modification (Leppänen et al 2011;Van den Bulcke et al 2011;Taylor et al 2013;Biziks et al 2016), archeological wood (Svedström et al 2011), cork (Oliveira et al 2016), fiberboards (Badel et al 2008, Walter andThoemen 2009), wood plastic composites (Defoirdt et al 2010;Schwarzkopf and Muszynski 2015), plywood (Van den Bulcke et al 2011), wood strand composites (Li et al 2016), and wax-impregnation (Scholz et al 2010a,b), just to mention a few. In general, the emerging synchrotron based TM with its high resolution has a great analytical power for wood research (Trtik et al 2007;Hass et al 2010;Zauner et al 2012;Endo and Sugiyama 2013;Baensch et al 2015).…”

Diffusion of chemicals into archaeological waterlogged hardwoods obtained from the Thang Long Imperial Citadel site, Vietnam

“…The diffusional replacement of water in WW has been investigated with a range of different chemical agents, including sugars (saccharose, lactose, trehalose) [9,10], polyethylene glycols (PEGs) of different molecular weights (PEG300-PEG6000) [3,[11][12][13][14][15], polymerizable monomers and cross-linkable precondensates (e.g., melamine and phenolic resins) [16], and keratin [17]. Furthermore, the conservation of WW has been performed using several types of diffusion technologies, including multi-spraying, long-term immersion, bandaging, panel impregnation, and pressurediffusion techniques [8].…”