Sorption and capillary condensation in wood and the moisture content of red pine

Abstract

The major purpose of this study is to improve hygrothermal simulation of wood responses to environmental vapor and moisture conditions under high relative humidity conditions. The article first reviews moisture property–related wood microstructures, sorption behavior, the concept of fiber saturation point, the potential for vapor to condense in wood under high relative humidity conditions, the measurement of equilibrium moisture content using traditional sorption methods, and the use of pressure plate test method at relative humidities above 95%. It then summarizes the results of equilibrium moisture content measurements for red pine sapwood at high relative humidity conditions using both sorption and pressure plate methods, with capillary saturation as maximum moisture content. It also discusses a number of wood microstructure and end-use-related factors that could influence the moisture content in service and the measurement of equilibrium moisture content in laboratory. Inconsistencies were found with other equilibrium moisture content data using the pressure plate test method.