Abstract

Moisture diffusion in wood refers to the molecular movement of water below the fiber-saturation point. This process is fundamental to understanding drying behavior, surface treatment response, and overall performance in engineered products and architectural applications. In this research, the transverse moisture diffusion coefficient of Eucalyptus nitens was measured under isothermal conditions (20 degrees C at 50% and 30% relative humidity) across two anatomical directions (radial and tangential), and three radial positions (inner, middle, and outer wood) of 17-year-old trees from different provenances in Chile. The vapometer method was used, applying Fick's law, and results were related to basic density and apparent density obtained from X-ray profiles. Diffusion was higher in the radial direction than in the tangential and decreased with increasing humidity. A significant inverse correlation was found between wood density and diffusion coefficient, particularly in the middle zone, which consistently showed the lowest values. These results support targeted drying approaches for Eucalyptus nitens based on anatomical direction and radial positions.