Effect of Steaming and Hot-Water Soaking on Extractive Distribution and Moisture Diffusivity in Southern Pine During Drying

Samples of southern pine sapwood and heartwood were treated five different ways: steaming in the saturated condition for 1 h and 5 h, respectively, steaming at a moisture content near the fiber saturation point (FSP) for 1 h, hot-water soaking for 10 h, and steaming near 95% relative humidity at an equilibrium moisture content (EMC) slightly below the FSP for 1 h at 100°C. The samples were dried from near saturation condition to an EMC slightly below the FSP, and then to final 12% EMC. The results indicate that the amount of extractives removed tended to be evenly distributed along the flow direction before drying and after drying to near FSP, which suggests that extractives move with water in wood in response to moisture gradient during drying. Hot-water soaking and prolonged steaming increased the moisture diffusivities above and below the FSP. The variation in diffusion coefficient was partially due to changes in the extractive distribution profile.