THE EFFECT OF DRYING SCHEDULE ON THE RADIAL PERMEABILITY OF PINUS-RADIATA D DON

The effect of air-, kiln-, and high-temperature drying on the radial permeability of Pinus radiata D. Don was studied. It was found that for both heartwood and sapwood the permeability increased as the severity of drying increased. The sapwood permeability rose from 5.3 x 10(-14) m2 for air-dried timber to 10.9 x 10(-14) m2 for high-temperature-dried timber, an increase of approximately 100%. The rise in heartwood permeability was approximately 280%, with the air-dried permeability being 1.3 x 10(-14) m2 and the high-temperature-dried permeability being 5.3 x 10(-14) m2. It is considered that this higher radial permeability of high temperature-dried wood is responsible for its increased ease of impregnation with preservatives. As the predominant route for gas movement in P. radiata is the resin canal network, it is suggested that this increase in permeability is due to movement and modification of the resin. The flow through the samples was entirely laminar, with no evidence of either molecular or turbulent flow for pressure differentials from 10 to 100 kPa.