Swelling of oak wood in alcoholic solutions: synergy and memory effects between water and ethanol

This work is devoted to dimensional changes in oak wood induced by the adsorption of water and ethanol molecules during barrel aging of wine and spirits. A custom device has been developed to determine the deformations in the radial and tangential directions of samples soaked in liquid, through imagery and digital image correlation. Swelling measurements and residual shrinkage after subsequent drying are reported at eight ethanol contents, including pure water and ethanol. A synergistic effect is observed over a wide range of concentrations. This suggests a collaborative action of sorption sites when both water and ethanol are in sufficient quantity. In addition, sequential exposure tests were performed to assess the effect of history, showing that the order of exposure influences the swelling because of the irreversible alterations in the structure of the wood. All these data, including the residual shrinkage, were analyzed and the mechanisms are summarized in a graphical presentation.