Wood-water relationship and micro-chemical properties of huminated archaeological European elm (Ulmus laevis P.)

Abstract

Archaeological wood requires effective conservation to prevent further degradation, and traditional modifications such as polyethylene glycol (PEG) have limitations, including hygroscopicity and chemical degradation over time. To explore alternative modification, this study was conducted to investigate the suitability of humins, crosslinked with different concentrations of succinic acid (SA), to protect archaeological elm wood from the Agapia Monastery against water and to determine the modification mechanism. Key parameters such as dimensional stability, moisture sorption isotherms, and determination of accessible hydroxy groups as a function of humination modification were analyzed using dynamic vapor sorption (DVS). The modification mechanism was studied by microstructural and chemical properties evaluation by Confocal-Raman spectroscopy and scanning electron microscopy (SEM). Results indicated that humins, particularly crosslinked with SA, significantly improved the water-related properties of wood and its dimensional stability. The humination also reduced the accessibility of the hydroxy group, thus decreasing the equilibrium moisture content (EMC) of huminated elm at relative humidities (RHs) ranging from 0 to 95%. While SEM images revealed structural changes in the modified wood, Confocal-Raman spectroscopy confirmed the successful allocation of humins into the cell walls. This study demonstrates that humins are promising materials for archaeological wood conservation, providing improvements in both chemical and physical properties.