Water Distribution in Wood after Short Term Wetting

Water has a major influence on wood properties, especially dynamic moisture cycles, which affect the wood in outdoor applications. It is thus important to understand the penetration and distribution of water in wood. In this study, rainfall events were simulated to correspond to water immersion periods of 1 h. Specimens were imaged by magnetic resonance imaging (MRI) after 1 h of immersion. These measurements were used to determine the water distribution in the wood and to elucidate changes during the drying of specimens of five wood species: sweet chestnut heartwood (Castanea sativa), European larch heartwood (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris) and Norway spruce (Picea abies). Both gravimetric and MRI analysis showed that after 1 h of immersion, pine sapwood took up the highest amount of water, followed by spruce wood. Considerably lower moisture contents were determined in pine heartwood, chestnut and larch, which correlated with a lower signal intensity. The outer parts of the specimens exhibited similar patterns with all of the specimens. The most variable results were the moisture content time profiles in the middle part of the specimens. Comparison of the MRI measurements and gravimetrically determined moisture contents during drying validated the MRI measurements and confirmed the method to be suitable for giving comprehensive information about the water drying kinetic.