These difficulties may also be attributed
mainly to the slow movement of moisture through porous materials, which makes
the experimental period be extensively long. The entry of water into wood may
result from mass flow or diffusion of water vapour into the cell lumens and
diffusion from there into the cell wall, or from a diffusion of bound water entirely
within the cell wall. In most cases, both processes probably occur. The mass flow
penetration, followed by the diffusion into the cell wall, is a much more rapid
process than either vapour-phase or bound-water diffusion (Banks, 1973). Water
absorption experiments are valuable in predicting moisture uptake regardless of
the mechanisms.