Impregnation of radiata pine wood by vacuum treatment II: effect of pre-steaming on wood structure and resin content

Radiata pine sapwood and heartwood were dried using high-temperature, conve ntional-temperature, and air drying schedules with and without pre-steaming . They were then impregnated by vacuum treatment with double-distilled wate r, toluidine blue, and fluorescein dye. For sapwood, there were only minor differences in uptake between drying methods and when pre-steaming was used . Using microscopy, the primary flow pathways in sapwood were found to be t he resin canal network and ray parenchyma cells, which provided conduction without large resistance. In heartwood, uptake was strongly influenced by p re-steaming the green lumber. After pre-steaming heart-wood, there was an i ncrease in uptake from all surfaces but especially from the radial surfaces , Lower extractive contents, disruption of epithelial and ray parenchyma ce lls, and alteration of the condition of bordered pits were also associated with pre-steaming. It was therefore passible to classify how paths in radia ta pine heartwood five ways, according to uptake values and wood anatomical features.