THE PENETRATION OF WATER VAPOR INTO WOOD

Abstract

The rate of diffusion of water vapor through wood has been studied through a comparison of the time taken for samples of various thickness to become saturated. This process is, in a sense, the converse of natural drying, and for comparative purposes is more amenable to careful control of pressure and temperature. Continuous measurements of the amount of adsorption were carried out by the use of a quartz spring balance completely enclosed in the apparatus at a constant vapor pressure.Comparative numerical values have been obtained of the rate of diffusion of water vapor through spruce (Picea canadensis) and pine (Pinus banxiana) in various directions, through heartwood and sapwood, and through samples of different lengths. The results are considered as evidence that the movement of water through wood at concentrations below the saturation point, takes place as vapor diffusion through the spaces of the wood structure due to the pressure gradient consequent on the difference of moisture content.